Next: Summary, Up: (dir)

## Debugging with DDD

DDD is a graphical front-end for GDB and other command-line debuggers.

This is the First Edition of Debugging with DDD, 8 Feb, 2009, for DDD Version 3.3.12.

## Table of Contents

- Debugging with DDD
- Summary of DDD
  - About this Manual
  - Typographic conventions
  - Free software
  - Getting DDD
  - Contributors to DDD
  - History of DDD
- 1 A Sample DDD Session
  - 1.1 Sample Program
- 2 Getting In and Out of DDD
  - 2.1 Invoking DDD
    - 2.1.1 Choosing an Inferior Debugger
    - 2.1.2 DDD Options
    - 2.1.3 X Options
    - 2.1.4 Inferior Debugger Options
      - 2.1.4.1 GDB Options
      - 2.1.4.2 DBX and Ladebug Options
      - 2.1.4.3 XDB Options
      - 2.1.4.4 JDB Options
      - 2.1.4.5 Bash Options
      - 2.1.4.6 GNU Make Options
      - 2.1.4.7 Perl Options
      - 2.1.4.8 PYDB Options
    - 2.1.5 Multiple DDD Instances
    - 2.1.6 X warnings
  - 2.2 Quitting DDD
  - 2.3 Persistent Sessions
    - 2.3.1 Saving Sessions
    - 2.3.2 Resuming Sessions
    - 2.3.3 Deleting Sessions
    - 2.3.4 Customizing Sessions
  - 2.4 Remote Debugging
    - 2.4.1 Running DDD on a Remote Host
    - 2.4.2 Using DDD with a Remote Inferior Debugger
      - 2.4.2.1 Customizing Remote Debugging
    - 2.4.3 Debugging a Remote Program
  - 2.5 Customizing Interaction with the Inferior Debugger
    - 2.5.1 Invoking an Inferior Debugger
    - 2.5.2 Initializing the Inferior Debugger
      - 2.5.2.1 Bash Initialization
      - 2.5.2.2 DBX Initialization
      - 2.5.2.3 GDB Initialization
      - 2.5.2.4 JDB Initialization
      - 2.5.2.5 GNU Make Initialization
      - 2.5.2.6 Perl Initialization
      - 2.5.2.7 PYDB Initialization
      - 2.5.2.8 XDB Initialization
      - 2.5.2.9 Finding a Place to Start
      - 2.5.2.10 Opening the Selection
    - 2.5.3 Communication with the Inferior Debugger
- 3 The DDD Windows
  - 3.1 The Menu Bar
    - 3.1.1 The File Menu
    - 3.1.2 The Edit Menu
    - 3.1.3 The View Menu
    - 3.1.4 The Program Menu
    - 3.1.5 The Commands Menu
    - 3.1.6 The Status Menu
    - 3.1.7 The Source Menu
    - 3.1.8 The Data Menu
    - 3.1.9 The Maintenance Menu
    - 3.1.10 The Help Menu
    - 3.1.11 Customizing the Menu Bar
      - 3.1.11.1 Auto-Raise Menus
      - 3.1.11.2 Customizing the Edit Menu
  - 3.2 The Tool Bar
    - 3.2.1 Customizing the Tool Bar
  - 3.3 The Command Tool
    - 3.3.1 Customizing the Command Tool
      - 3.3.1.1 Disabling the Command Tool
    - 3.3.2 Command Tool Position
      - 3.3.2.1 Customizing Tool Decoration
  - 3.4 Getting Help
  - 3.5 Undoing and Redoing Commands
  - 3.6 Customizing DDD
    - 3.6.1 How Customizing DDD Works
      - 3.6.1.1 Resources
      - 3.6.1.2 Changing Resources
      - 3.6.1.3 Saving Options
    - 3.6.2 Customizing DDD Help
      - 3.6.2.1 Button Tips
      - 3.6.2.2 Tip of the day
      - 3.6.2.3 Help Helpers
    - 3.6.3 Customizing Undo
    - 3.6.4 Customizing the DDD Windows
      - 3.6.4.1 Splash Screen
      - 3.6.4.2 Window Layout
      - 3.6.4.3 Customizing Fonts
      - 3.6.4.4 Toggling Windows
      - 3.6.4.5 Text Fields
      - 3.6.4.6 Icons
      - 3.6.4.7 Adding Buttons
      - 3.6.4.8 More Customizations
    - 3.6.5 Debugger Settings
- 4 Navigating through the Code
  - 4.1 Compiling for Debugging
  - 4.2 Opening Files
    - 4.2.1 Opening Programs
    - 4.2.2 Opening Core Dumps
    - 4.2.3 Opening Source Files
    - 4.2.4 Filtering Files
  - 4.3 Looking up Items
    - 4.3.1 Looking up Definitions
    - 4.3.2 Textual Search
    - 4.3.3 Looking up Previous Locations
    - 4.3.4 Specifying Source Directories
  - 4.4 Customizing the Source Window
    - 4.4.1 Customizing Glyphs
    - 4.4.2 Customizing Searching
    - 4.4.3 Customizing Source Appearance
    - 4.4.4 Customizing Source Scrolling
    - 4.4.5 Customizing Source Lookup
    - 4.4.6 Customizing File Filtering
- 5 Stopping the Program
  - 5.1 Breakpoints
    - 5.1.1 Setting Breakpoints
      - 5.1.1.1 Setting Breakpoints by Location
      - 5.1.1.2 Setting Breakpoints by Name
      - 5.1.1.3 Setting Regexp Breakpoints
    - 5.1.2 Deleting Breakpoints
    - 5.1.3 Disabling Breakpoints
    - 5.1.4 Temporary Breakpoints
    - 5.1.5 Editing Breakpoint Properties
    - 5.1.6 Breakpoint Conditions
    - 5.1.7 Breakpoint Ignore Counts
    - 5.1.8 Breakpoint Commands
    - 5.1.9 Moving and Copying Breakpoints
    - 5.1.10 Looking up Breakpoints
    - 5.1.11 Editing all Breakpoints
    - 5.1.12 Hardware-Assisted Breakpoints
  - 5.2 Watchpoints
    - 5.2.1 Setting Watchpoints
    - 5.2.2 Editing Watchpoint Properties
    - 5.2.3 Editing all Watchpoints
    - 5.2.4 Deleting Watchpoints
  - 5.3 Interrupting
  - 5.4 Stopping X Programs
    - 5.4.1 Customizing Grab Checking
- 6 Running the Program
  - 6.1 Starting Program Execution
    - 6.1.1 Your Program's Arguments
    - 6.1.2 Your Program's Environment
    - 6.1.3 Your Program's Working Directory
    - 6.1.4 Your Program's Input and Output
  - 6.2 Using the Execution Window
    - 6.2.1 Customizing the Execution Window
  - 6.3 Attaching to a Running Process
    - 6.3.1 Customizing Attaching to Processes
  - 6.4 Program Stops
  - 6.5 Resuming Execution
    - 6.5.1 Continuing
    - 6.5.2 Stepping one Line
    - 6.5.3 Continuing to the Next Line
    - 6.5.4 Continuing Until Here
    - 6.5.5 Continuing Until a Greater Line is Reached
    - 6.5.6 Continuing Until Function Returns
  - 6.6 Continuing at a Different Address
  - 6.7 Examining the Stack
    - 6.7.1 Stack Frames
    - 6.7.2 Backtraces
    - 6.7.3 Selecting a Frame
  - 6.8 “Undoing” Program Execution
  - 6.9 Examining Threads
  - 6.10 Handling Signals
  - 6.11 Killing the Program
- 7 Examining Data
  - 7.1 Showing Simple Values using Value Tips
  - 7.2 Printing Simple Values in the Debugger Console
  - 7.3 Displaying Complex Values in the Data Window
    - 7.3.1 Display Basics
      - 7.3.1.1 Creating Single Displays
      - 7.3.1.2 Selecting Displays
      - 7.3.1.3 Showing and Hiding Details
      - 7.3.1.4 Rotating Displays
      - 7.3.1.5 Displaying Local Variables
      - 7.3.1.6 Displaying Program Status
      - 7.3.1.7 Refreshing the Data Window
      - 7.3.1.8 Display Placement
      - 7.3.1.9 Clustering Displays
      - 7.3.1.10 Creating Multiple Displays
      - 7.3.1.11 Editing all Displays
      - 7.3.1.12 Deleting Displays
    - 7.3.2 Arrays
      - 7.3.2.1 Array Slices
      - 7.3.2.2 Repeated Values
      - 7.3.2.3 Arrays as Tables
    - 7.3.3 Assignment to Variables
    - 7.3.4 Examining Structures
      - 7.3.4.1 Displaying Dependent Values
      - 7.3.4.2 Dereferencing Pointers
      - 7.3.4.3 Shared Structures
      - 7.3.4.4 Display Shortcuts
    - 7.3.5 Customizing Displays
      - 7.3.5.1 Using Data Themes
      - 7.3.5.2 Applying Data Themes to Several Values
      - 7.3.5.3 Editing Themes
      - 7.3.5.4 Writing Data Themes
      - 7.3.5.5 Display Resources
      - 7.3.5.6 VSL Resources
    - 7.3.6 Layouting the Graph
      - 7.3.6.1 Moving Displays
      - 7.3.6.2 Scrolling Data
      - 7.3.6.3 Aligning Displays
      - 7.3.6.4 Automatic Layout
      - 7.3.6.5 Rotating the Graph
    - 7.3.7 Printing the Graph
  - 7.4 Plotting Values
    - 7.4.1 Plotting Arrays
    - 7.4.2 Changing the Plot Appearance
    - 7.4.3 Plotting Scalars and Composites
    - 7.4.4 Plotting Display Histories
    - 7.4.5 Printing Plots
    - 7.4.6 Entering Plotting Commands
    - 7.4.7 Exporting Plot Data
    - 7.4.8 Animating Plots
    - 7.4.9 Customizing Plots
      - 7.4.9.1 Gnuplot Invocation
      - 7.4.9.2 Gnuplot Settings
  - 7.5 Examining Memory
- 8 Machine-Level Debugging
  - 8.1 Examining Machine Code
  - 8.2 Machine Code Execution
  - 8.3 Examining Registers
  - 8.4 Customizing Machine Code
- 9 Changing the Program
  - 9.1 Editing Source Code
    - 9.1.1 Customizing Editing
    - 9.1.2 In-Place Editing
  - 9.2 Recompiling
  - 9.3 Patching
- 10 The Command-Line Interface
  - 10.1 Entering Commands
    - 10.1.1 Command Completion
    - 10.1.2 Command History
    - 10.1.3 Typing in the Source Window
  - 10.2 Entering Commands at the TTY
  - 10.3 Integrating DDD
    - 10.3.1 Using DDD with Emacs
    - 10.3.2 Using DDD with XEmacs
    - 10.3.3 Using DDD with XXGDB
  - 10.4 Defining Buttons
    - 10.4.1 Customizing Buttons
  - 10.5 Defining Commands
    - 10.5.1 Defining Simple Commands using GDB
    - 10.5.2 Defining Argument Commands using GDB
    - 10.5.3 Defining Commands using Other Debuggers
- Appendix A Application Defaults
  - A.1 Actions
    - A.1.1 General Actions
    - A.1.2 Data Display Actions
    - A.1.3 Debugger Console Actions
    - A.1.4 Source Window Actions
  - A.2 Images
- Appendix B Bugs and How To Report Them
  - B.1 Where to Send Bug Reports
  - B.2 Is it a DDD Bug?
  - B.3 How to Report Bugs
  - B.4 What to Include in a Bug Report
  - B.5 Getting Diagnostics
    - B.5.1 Logging
      - B.5.1.1 Disabling Logging
    - B.5.2 Debugging DDD
    - B.5.3 Customizing Diagnostics
- Appendix C Configuration Notes
  - C.1 Using DDD with GDB
    - C.1.1 Using DDD with WDB
    - C.1.2 Using DDD with WindRiver GDB (Tornado)
  - C.2 Using DDD with Bash
  - C.3 Using DDD with DBX
  - C.4 Using DDD with Ladebug
  - C.5 Using DDD with JDB
  - C.6 Using DDD with GNU Make
  - C.7 Using DDD with Perl
  - C.8 Using DDD with Python
  - C.9 Using DDD with XDB
  - C.10 Using DDD with LessTif
- Appendix D Dirty Tricks
- Appendix E Extending DDD
- Appendix F Frequently Answered Questions
- Appendix G GNU General Public License
- Appendix H Help and Assistance
- Appendix I GNU Free Documentation License
  - ADDENDUM: How to use this License for your documents
- Label Index
- Key Index
- Command Index
- Resource Index
- File Index
- Concept Index

Copyright © 2004 Universität des Saarlandes
Lehrstuhl Softwaretechnik
Postfach 15 11 50
66041 Saarbrücken
GERMANY

Distributed by
Free Software Foundation, Inc.
59 Temple Place - Suite 330
Boston, MA 02111-1307
USA

DDD and this manual are available via the DDD WWW page.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts and no Back-Cover Texts. A copy of the license is included in the section entitled “GNU Free Documentation License”; See Documentation License, for details.

Send questions, comments, suggestions, etc. to ddd@gnu.org.
Submit bug reports at http://savannah.gnu.org/bugs/?group=ddd, the DDD bug tracker. Incoming bug reports are automatically copied to the developers' mailing list bug-ddd@gnu.org.

Next: Sample Session, Previous: Top, Up: Top

## Summary of DDD

The purpose of a debugger such as DDD is to allow you to see what is going on “inside” another program while it executes—or what another program was doing at the moment it crashed.

DDD can do four main kinds of things (plus other things in support of these) to help you catch bugs in the act:

- Start your program, specifying anything that might affect its behavior.
- Make your program stop on specified conditions.
- Examine what has happened, when your program has stopped.
- Change things in your program, so you can experiment with correcting the effects of one bug and go on to learn about another.

Technically speaking, DDD is a front-end to a command-line debugger (called inferior debugger, because it lies at the layer beneath DDD). DDD supports the following inferior debuggers:

- To debug executable binaries, you can use DDD with GDB, DBX, Ladebug, or XDB.
  - GDB, the GNU debugger, is the recommended inferior debugger for DDD. GDB supports native executables binaries originally written in C, C++, Java, Modula-2, Modula-3, Pascal, Chill, Ada, and FORTRAN. (see Using GDB with Different Languages, for information on language support in GDB.)
  - As an alternative to GDB, you can use DDD with the DBX debugger, as found on several UNIX systems. Most DBX incarnations offer fewer features than GDB, and some of the more advanced DBX features may not be supported by DDD. However, using DBX may be useful if GDB does not understand or fully support the debugging information as generated by your compiler.
  - As an alternative to GDB and DBX, you can use DDD with Ladebug, as found on Compaq and DEC systems. Ladebug offers fewer features than GDB, and some of the more advanced Ladebug features may not be supported by DDD. However, using Ladebug may be useful if GDB or DBX do not understand or fully support the debugging information as generated by your compiler.1
  - As another alternative to GDB, you can use DDD with the XDB debugger, as found on HP-UX systems.2.
- To debug Java byte code programs, you can use DDD with JDB, the Java debugger, as of JDK 1.1 and later. (DDD has been tested with JDK 1.1 and JDK 1.2.)
- To debug Bash programs, you need a version Bash that supports extended debugging support; see http://bashdb.sourceforge.net. It important to make sure you get the right version of the debugger that matches your version of Bash. For bash version 2.05b, you need a patched version of bash as well as the debugger for bash.
- To debug GNU Make Makefiles, you need a version GNU Make that supports extended debugging support. To get this enhanced version see http://bashdb.sourceforge.net/remake.
- To debug Perl programs, you can use DDD with the Perl debugger, as of Perl 5.003 and later.
- To debug Python programs, you need an extended version of the python debugger called `pydb`. To get this, see http://bashdb.sourceforge.net/pydb.

See Choosing an Inferior Debugger, for choosing the appropriate inferior debugger. See Sample Session, for getting a first impression of DDD.

Next: Typographic Conventions, Up: Summary

### About this Manual

This manual comes in several formats:

- The Info format is used for browsing on character devices; it comes without pictures. You should have a local copy installed, which you can browse via Emacs, the stand-alone `info` program, or from DDD via ‘`Help DDD Reference`’.

  The DDD source distribution `ddd-3.3.12.tar.gz` contains this manual as pre-formatted info files; you can also download them from
  the DDD WWW page.

- The PostScript format is used for printing on paper; it comes with pictures as well.

  The DDD source distribution `ddd-3.3.12.tar.gz` contains this manual as pre-formatted PostScript file; you can also download it from
  the DDD WWW page.

- The PDF format is used for printing on paper as well as for online browsing; it comes with pictures as well.

  The DDD source distribution `ddd-3.3.12.tar.gz` contains this manual as pre-formatted PDF file; you can also download it from
  the DDD WWW page.

- The HTML format is used for browsing on bitmap devices; it includes several pictures. You can view it using a HTML browser, typically from a local copy.

  A pre-formatted HTML version of this manual comes in a separate DDD package
  `ddd-3.3.12-html-manual.tar.gz`; you can browse and download it via
  the DDD WWW page.

The manual itself is written in TeXinfo format; its source code `ddd.texi` is contained in the DDD source distribution `ddd-3.3.12.tar.gz`.

The picture sources come in a separate package `ddd-3.3.12-pics.tar.gz`; you need this package only if you want to re-create the PostScript, HTML, or PDF versions.

Next: Free Software, Previous: About this Manual, Up: Summary

### Typographic conventions

<Ctrl+A>
  The name for a key on the keyboard (or multiple keys pressed simultaneously)
`run`
  A sequence of characters to be typed on the keyboard.
`~/.ddd/init`
  A file.
‘`Help`’
  A graphical control element, such as a button or menu item.
‘`File Open Program`’
  A sequence of menu items, starting at the top-level menu bar.
`argc - 1`
  Program code or debugger command.
`-g`
  A command-line option.
`$`
  System prompt.
`(gdb)`
  Debugger prompt.
`_`
  Cursor position.
version
  A metasyntactic variable; something that stands for another piece of text.
definition
  A definition.
caution
  Emphasis.
A warning
  Strong emphasis.
DDD
  An acronym.

Here's an example. ‘``break` location`’ is a typed command at the ‘``(gdb)`` ’ prompt; the metasyntactic variable ‘`location`’ would be replaced by the actual location. ‘``_``’ is the cursor position after entering the command.

         (gdb) break location
         Breakpoint number at location
         (gdb) _

Next: Getting <acronym>DDD</acronym>, Previous: Typographic Conventions, Up: Summary

### Free software

DDD is free; this means that everyone is free to use it and free to redistribute it on a free basis. DDD is not in the public domain; it is copyrighted and there are restrictions on its distribution, but these restrictions are designed to permit everything that a good cooperating citizen would want to do. What is not allowed is to try to prevent others from further sharing any version of DDD that they might get from you. The precise conditions are found in the GNU General Public License that comes with DDD; See License, for details.

The easiest way to get a copy of DDD is from someone else who has it. You need not ask for permission to do so, or tell any one else; just copy it.

Next: Contributors, Previous: Free Software, Up: Summary

### Getting DDD

If you have access to the Internet, you can get the latest version of DDD from the anonymous FTP server ‘`ftp.gnu.org`’ in the directory `/gnu/ddd`. This should contain the following files:

``ddd-version.tar.gz``
  The DDD source distribution. This should be all you need.
``ddd-version-html-manual.tar.gz``
  The DDD manual in HTML format. You need this only if you want to install a local copy of the DDD manual in HTML format.
``ddd-version-pics.tar.gz``
  Sources of images included in the DDD manual. You need this only if you want to recreate the DDD manual.

DDD can also be found at numerous other archive sites around the world; check the file `ANNOUNCE` in a DDD distribution for the latest known list.

Next: History, Previous: Getting <acronym>DDD</acronym>, Up: Summary

### Contributors to DDD

Dorothea Lütkehaus and Andreas Zeller were the original authors of DDD. Many others have contributed to its development. The files `ChangeLog` and `THANKS` in the DDD distribution approximates a blow-by-blow account.

Previous: Contributors, Up: Summary

### History of DDD

The history of DDD is a story of code recycling. The oldest parts of DDD were written in 1990, when Andreas Zeller designed VSL, a box-based visual structure language for visualizing data and program structures. The VSL interpreter and the Box library became part of Andreas' Diploma Thesis, a graphical syntax editor based on the Programming System Generator PSG.

In 1992, the VSL and Box libraries were recycled for the NORA project. For NORA, an experimental inference-based software development tool set, Andreas wrote a graph editor (based on VSL and the Box libraries) and facilities for inter-process knowledge exchange. Based on these tools, Dorothea Lütkehaus (now Dorothea Krabiell) realized DDD as her Diploma Thesis, 1994.

The original DDD had no source window; this was added by Dorothea during the winter of 1994–1995. In the first quarter of 1995, finally, Andreas completed DDD by adding command and execution windows, extensions for DBX and remote debugging as well as configuration support for several architectures. Since then, Andreas has further maintained and extended DDD, based on the comments and suggestions of several DDD users around the world. See the comments in the DDD source for details.

Major DDD events:

April, 1995
  DDD 0.9: First DDD beta release.
May, 1995
  DDD 1.0: First public DDD release.
December, 1995
  DDD 1.4: Machine-level debugging, glyphs, Emacs integration.
October, 1996
  DDD 2.0: Color displays, XDB support, generic DBX support, command tool.
May, 1997
  DDD 2.1: Alias detection, button tips, status displays.
November, 1997
  DDD 2.2: Sessions, display shortcuts.
June, 1998
  DDD 3.0: Icon tool bar, Java support, JDB support.
December, 1998
  DDD 3.1: Data plotting, Perl support, Python support, Undo/Redo.
January, 2000
  DDD 3.2: New manual, Readline support, Ladebug support.
January, 2001
  DDD 3.3: Data themes, JDB 1.2 support, VxWorks support.
November, 2002
  DDD 3.3.2: Bash support.
March, 2003
  DDD 3.3.3: Better Bash support. Compiles using modern tools thanks to Daniel Schepler.
Dec, 2005
  DDD 3.3.12-test: GNU Make support added.
Feb, 2006
  DDD 3.3.12-test3: Modernize Python debugging
Feb, 2009
  DDD 3.3.12: First mainstream release to include improved support for Python, Bash and Make.

Next: Invocation, Previous: Summary, Up: Top

## 1 A Sample DDD Session

You can use this manual at your leisure to read all about DDD. However, a handful of features are enough to get started using the debugger. This chapter illustrates those features.

The sample program `sample.c` (see Sample Program) exhibits the following bug. Normally, `sample` should sort and print its arguments numerically, as in the following example:

         $ ./sample 8 7 5 4 1 3
         1 3 4 5 7 8
         $ _

However, with certain arguments, this goes wrong:

         $ ./sample 8000 7000 5000 1000 4000
         1000 1913 4000 5000 7000
         $ _

Although the output is sorted and contains the right number of arguments, some arguments are missing and replaced by bogus numbers; here, `8000` is missing and replaced by `1913`.3

Let us use DDD to see what is going on. First, you must compile `sample.c` for debugging (see Compiling for Debugging), giving the `-g` flag while compiling:

         $ gcc -g -o sample sample.c
         $ _

Now, you can invoke DDD (see Invocation) on the `sample` executable:

         $ ddd sample

After a few seconds, DDD comes up. The Source Window contains the source of your debugged program; use the Scroll Bar to scroll through the file.

The Debugger Console (at the bottom) contains DDD version information as well as a GDB prompt.4

         GNU DDD Version 3.3.12, by Dorothea Lütkehaus and Andreas Zeller.
         Copyright © 1995-1999 Technische Universität Braunschweig, Germany.
         Copyright © 1999-2001 Universität Passau, Germany.
         Copyright © 2001-2004 Universität des Saarlandes, Germany.
         Reading symbols from sample...done.
         (gdb) _

The first thing to do now is to place a Breakpoint (see Breakpoints), making `sample` stop at a location you are interested in. Click on the blank space left to the initialization of `a`. The Argument field ‘`():`’ now contains the location (‘`sample.c:31`’). Now, click on ‘`Break`’ to create a breakpoint at the location in ‘`()`’. You see a little red stop sign appear in line 31.

The next thing to do is to actually execute the program, such that you can examine its behavior (see Running). Select ‘`Program Run`’ to execute the program; the ‘`Run Program`’ dialog appears.

In ‘`Run with Arguments`’, you can now enter arguments for the `sample` program. Enter the arguments resulting in erroneous behavior here—that is, ‘`8000 7000 5000 1000 4000`’. Click on ‘`Run`’ to start execution with the arguments you just entered.

GDB now starts `sample`. Execution stops after a few moments as the breakpoint is reached. This is reported in the debugger console.

         (gdb) break sample.c:31
         Breakpoint 1 at 0x8048666: file sample.c, line 31.
         (gdb) run 8000 7000 5000 1000 4000
         Starting program: sample 8000 7000 5000 1000 4000

         Breakpoint 1, main (argc=6, argv=0xbffff918) at sample.c:31
         (gdb) _

The current execution line is indicated by a green arrow.

          a = (int *)malloc((argc - 1) * sizeof(int));

You can now examine the variable values. To examine a simple variable, you can simply move the mouse pointer on its name and leave it there. After a second, a small window with the variable value pops up (see Value Tips). Try this with ‘`argc`’ to see its value (`6`). The local variable ‘`a`’ is not yet initialized; you'll probably see `0x0` or some other invalid pointer value.

To execute the current line, click on the ‘`Next`’ button on the command tool. The arrow advances to the following line. Now, point again on ‘`a`’ to see that the value has changed and that ‘`a`’ has actually been initialized.

To examine the individual values of the ‘`a`’ array, enter ‘`a[0]`’ in the argument field (you can clear it beforehand by clicking on ‘`():`’) and then click on the ‘`Print`’ button. This prints the current value of ‘`()`’ in the debugger console (see Printing Values). In our case, you'll get

         (gdb) print a[0]
         $1 = 0
         (gdb) _

or some other value (note that ‘`a`’ has only been allocated, but the contents have not yet been initialized).

To see all members of ‘`a`’ at once, you must use a special GDB operator. Since ‘`a`’ has been allocated dynamically, GDB does not know its size; you must specify it explicitly using the ‘`@`’ operator (see Array Slices). Enter ‘`a[0]@(argc - 1)`’ in the argument field and click on the ‘`Print`’ button. You get the first `argc - 1` elements of ‘`a`’, or

         (gdb) print a[0]@(argc - 1)
         $2 = {0, 0, 0, 0, 0}
         (gdb) _

Rather than using ‘`Print`’ at each stop to see the current value of ‘`a`’, you can also display ‘`a`’, such that its is automatically displayed. With ‘`a[0]@(argc - 1)`’ still being shown in the argument field, click on ‘`Display`’. The contents of ‘`a`’ are now shown in a new window, the Data Window. Click on ‘`Rotate`’ to rotate the array horizontally.

Now comes the assignment of ‘`a`’'s members:

           for (i = 0; i < argc - 1; i++)
                 a[i] = atoi(argv[i + 1]);

You can now click on ‘`Next`’ and ‘`Next`’ again to see how the individual members of ‘`a`’ are being assigned. Changed members are highlighted.

To resume execution of the loop, use the ‘`Until`’ button. This makes GDB execute the program until a line greater than the current is reached. Click on ‘`Until`’ until you end at the call of ‘`shell_sort`’ in

           shell_sort(a, argc);

At this point, ‘`a`’'s contents should be ‘`8000 7000 5000 1000 4000`’. Click again on ‘`Next`’ to step over the call to ‘`shell_sort`’. DDD ends in

           for (i = 0; i < argc - 1; i++)
                 printf("%d ", a[i]);

and you see that after ‘`shell_sort`’ has finished, the contents of ‘`a`’ are ‘`1000, 1913, 4000, 5000, 7000`’—that is, ‘`shell_sort`’ has somehow garbled the contents of ‘`a`’.

To find out what has happened, execute the program once again. This time, you do not skip through the initialization, but jump directly into the ‘`shell_sort`’ call. Delete the old breakpoint by selecting it and clicking on ‘`Clear`’. Then, create a new breakpoint in line 35 before the call to ‘`shell_sort`’. To execute the program once again, select ‘`Program Run Again`’.

Once more, DDD ends up before the call to ‘`shell_sort`’:

           shell_sort(a, argc);

This time, you want to examine closer what ‘`shell_sort`’ is doing. Click on ‘`Step`’ to step into the call to ‘`shell_sort`’. This leaves your program in the first executable line, or

          int h = 1;

while the debugger console tells us the function just entered:

         (gdb) step
         shell_sort (a=0x8049878, size=6) at sample.c:9
         (gdb) _

This output that shows the function where ‘`sample`’ is now suspended (and its arguments) is called a stack frame display. It shows a summary of the stack. You can use ‘`Status Backtrace`’ to see where you are in the stack as a whole; selecting a line (or clicking on ‘`Up`’ and ‘`Down`’) will let you move through the stack. Note how the ‘`a`’ display disappears when its frame is left.

Let us now check whether ‘`shell_sort`’'s arguments are correct. After returning to the lowest frame, enter ‘`a[0]@size`’ in the argument field and click on ‘`Print`’:

         (gdb) print a[0] @ size
         $4 = {8000, 7000, 5000, 1000, 4000, 1913}
         (gdb) _

Surprise! Where does this additional value `1913` come from? The answer is simple: The array size as passed in ‘`size`’ to ‘`shell_sort`’ is too large by one—`1913` is a bogus value which happens to reside in memory after ‘`a`’. And this last value is being sorted in as well.

To see whether this is actually the problem cause, you can now assign the correct value to ‘`size`’ (see Assignment). Select ‘`size`’ in the source code and click on ‘`Set`’. A dialog pops up where you can edit the variable value.

Change the value of ‘`size`’ to `5` and click on ‘`OK`’. Then, click on ‘`Finish`’ to resume execution of the ‘`shell_sort`’ function:

         (gdb) set variable size = 5
         (gdb) finish
         Run till exit from #0  shell_sort (a=0x8049878, size=5) at sample.c:9
         0x80486ed in main (argc=6, argv=0xbffff918) at sample.c:35
         (gdb) _

Success! The ‘`a`’ display now contains the correct values ‘`1000, 4000, 5000, 7000, 8000`’.

You can verify that these values are actually printed to standard output by further executing the program. Click on ‘`Cont`’ to continue execution.

         (gdb) cont
         1000 4000 5000 7000 8000

         Program exited normally.
         (gdb) _

The message ‘`Program exited normally.`’ is from GDB; it indicates that the `sample` program has finished executing.

Having found the problem cause, you can now fix the source code. Click on ‘`Edit`’ to edit `sample.c`, and change the line

         shell_sort(a, argc);

to the correct invocation

         shell_sort(a, argc - 1);

You can now recompile `sample`

         $ gcc -g -o sample sample.c
         $ _

and verify (via ‘`Program Run Again`’) that `sample` works fine now.

         (gdb) run
         `sample' has changed; re-reading symbols.
         Reading in symbols...done.
         Starting program: sample 8000 7000 5000 1000 4000
         1000 4000 5000 7000 8000

         Program exited normally.
         (gdb) _

All is done; the program works fine now. You can end this DDD session with ‘`Program Exit`’ or `Ctrl+Q`.

Up: Sample Session

### 1.1 Sample Program

Here's the source `sample.c` of the sample program.

         /* sample.c -- Sample C program to be debugged with DDD */

         #include <stdio.h>
         #include <stdlib.h>

         static void shell_sort(int a[], int size)
         {
             int i, j;
             int h = 1;
             do {
                 h = h * 3 + 1;
             } while (h <= size);
             do {
                 h /= 3;
                 for (i = h; i < size; i++)
                 {
                     int v = a[i];
                     for (j = i; j >= h && a[j - h] > v; j -= h)
                         a[j] = a[j - h];
                     if (i != j)
                         a[j] = v;
                 }
             } while (h != 1);
         }

         int main(int argc, char *argv[])
         {
             int *a;
             int i;

             a = (int *)malloc((argc - 1) * sizeof(int));
             for (i = 0; i < argc - 1; i++)
                 a[i] = atoi(argv[i + 1]);

             shell_sort(a, argc);

             for (i = 0; i < argc - 1; i++)
                 printf("%d ", a[i]);
             printf("\n");

             free(a);
             return 0;
         }

Next: Windows, Previous: Sample Session, Up: Top

## 2 Getting In and Out of DDD

This chapter discusses how to start DDD, and how to get out of it. The essentials are:

- Type ‘`ddd`’ to start DDD (see Invoking).
- Use ‘`File Exit`’ or `Ctrl+Q` to exit (see Quitting).

Next: Quitting, Up: Invocation

### 2.1 Invoking DDD

Normally, you can run DDD by invoking the program `ddd`.

You can also run DDD with a variety of arguments and options, to specify more of your debugging environment at the outset.

The most usual way to start DDD is with one argument, specifying an executable program:

         ddd program

If you use GDB, DBX, Ladebug, or XDB as inferior debuggers, you can also start with both an executable program and a core file specified:

         ddd program core

You can, instead, specify a process ID as a second argument, if you want to debug a running process:

         ddd program 1234

would attach DDD to process `1234` (unless you also have a file named `1234`; DDD does check for a core file first).

You can further control DDD by invoking it with specific options. To get a list of DDD options, invoke DDD as

         ddd --help

Most important are the options to specify the inferior debugger (see Choosing an Inferior Debugger), but you can also customize several aspects of DDD upon invocation (see Options).

DDD also understands the usual X options such as `-display` or `-geometry`. See X Options, for details.

All arguments and options that are not understood by DDD are passed to the inferior debugger; See Inferior Debugger Options, for a survey. To pass an option to the inferior debugger that conflicts with an X option, or with a DDD option listed here, use the `--debugger` option (see Options).

Next: Options, Up: Invoking

#### 2.1.1 Choosing an Inferior Debugger

The most frequently required options are those to choose a specific inferior debugger.

Normally, the inferior debugger is determined by the program to analyze:

- If the program requires a specific interpreter, such as Bash, Java, GNU Make, Perl, or Python, then you should use a Bash, JDB, GNU Make, Perl, `pydb`, Bash, or inferior debugger.

  Use

                ddd --bash program
                ddd --interpreter='path-to-debugger-bash --debugger' program

                ddd --jdb program

                ddd --make program
                ddd --interpreter='path-to-debugger-make --debugger' program

                ddd --perl program

                ddd --pydb program

  to run DDD with JDB, `pydb`, Perl, Bash, or GNU Make as an inferior debugger.

- If the program is an executable binary, you should use DBX, GDB, Ladebug, or XDB. In general, GDB (or its HP variant, WDB) provides the most functionality of these debuggers.

  Use

                ddd --dbx program

                ddd --gdb program

                ddd --ladebug program

                ddd --wdb program

                ddd --xdb program

  to run DDD with GDB, WDB, DBX, Ladebug, or XDB as inferior debugger.

If you invoke DDD without any of these options, but give a program to analyze, then DDD will automatically determine the inferior debugger:

- If program is a Python program, a Perl script, or a Java class, DDD will invoke the appropriate debugger.
- If program is an executable binary, DDD will invoke its default debugger for executables (usually GDB).

See Customizing Debugger Interaction, for more details on determining the inferior debugger.

Next: X Options, Previous: Choosing an Inferior Debugger, Up: Invoking

#### 2.1.2 DDD Options

You can further control how DDD starts up using the following options. All options may be abbreviated, as long as they are unambiguous; single dashes `-` instead of double dashes `--` may also be used. Almost all options control a specific DDD resource or resource class (see Customizing).

`--attach-windows`
  Attach the source and data windows to the debugger console, creating one single big DDD window. This is the default setting.

  Giving this option is equivalent to setting the DDD ‘`Separate`’ resource class to ‘`off`’. See Window Layout, for details.

`--attach-source-window`
  Attach only the source window to the debugger console.

  Giving this option is equivalent to setting the DDD ‘`separateSourceWindow`’ resource to ‘`off`’. See Window Layout, for details.

`--attach-data-window`
  Attach only the source window to the debugger console.

  Giving this option is equivalent to setting the DDD ‘`separateDataWindow`’ resource to ‘`off`’. See Window Layout, for details.

`--automatic-debugger`
  Determine the inferior debugger automatically from the given arguments.

  Giving this option is equivalent to setting the DDD ‘`autoDebugger`’ resource to ‘`on`’. See Customizing Debugger Interaction, for details.

`--button-tips`
  Enable button tips.

  Giving this option is equivalent to setting the DDD ‘`buttonTips`’ resource to ‘`on`’. See Customizing Help, for details.

`--configuration`
  Print the DDD configuration settings on standard output and exit.

  Giving this option is equivalent to setting the DDD ‘`showConfiguration`’ resource to ‘`on`’. See Diagnostics, for details.

`--check-configuration`
  Check the DDD environment (in particular, the X configuration), report any possible problem causes and exit.

  Giving this option is equivalent to setting the DDD ‘`checkConfiguration`’ resource to ‘`on`’. See Diagnostics, for details.

`--data-window`
  Open the data window upon start-up.

  Giving this option is equivalent to setting the DDD ‘`openDataWindow`’ resource to ‘`on`’. See Toggling Windows, for details.

`--dbx`
  Run DBX as inferior debugger.

  Giving this option is equivalent to setting the DDD ‘`debugger`’ resource to ‘`dbx`’. See Customizing Debugger Interaction, for details.

`--debugger name`
  Invoke the inferior debugger name. This is useful if you have several debugger versions around, or if the inferior debugger cannot be invoked under its usual name (i.e. `gdb`, `wdb`, `dbx`, `xdb`, `jdb`, `pydb`, or `perl`).

  This option can also be used to pass options to the inferior debugger that would otherwise conflict with DDD options. For instance, to pass the option `-d directory` to XDB, use:

                ddd --debugger "xdb -d directory"

  If you use the `--debugger` option, be sure that the type of inferior debugger is specified as well. That is, use one of the options `--gdb`, `--dbx`, `--xdb`, `--jdb`, `--pydb`, or `--perl` (unless the default setting works fine).

  Giving this option is equivalent to setting the DDD ‘`debuggerCommand`’ resource to name. See Customizing Debugger Interaction, for details.

`--debugger-console`
  Open the debugger console upon start-up.

  Giving this option is equivalent to setting the DDD ‘`openDebuggerConsole`’ resource to ‘`on`’. See Toggling Windows, for details.

`--disassemble`
  Disassemble the source code. See also the `--no-disassemble` option, below.

  Giving this option is equivalent to setting the DDD ‘`disassemble`’ resource to ‘`on`’. See Customizing Source, for details.

`--exec-window`
  Run the debugged program in a specially created execution window. This is useful for programs that have special terminal requirements not provided by the debugger window, as raw keyboard processing or terminal control sequences. See Using the Execution Window, for details.

  Giving this option is equivalent to setting the DDD ‘`separateExecWindow`’ resource to ‘`on`’. See Customizing the Execution Window, for details.

`--font fontname`
`-fn fontname`
  Use fontname as default font.

  Giving this option is equivalent to setting the DDD ‘`defaultFont`’ resource to ‘`fontname`’. See Customizing Fonts, for details.

`--fonts`
  Show the font definitions used by DDD on standard output.

  Giving this option is equivalent to setting the DDD ‘`showFonts`’ resource to ‘`on`’. See Diagnostics, for details.

`--fontsize size`
  Set the default font size to size (in 1/10 points). To make DDD use 12-point fonts, say `--fontsize 120`.

  Giving this option is equivalent to setting the DDD ‘`FontSize`’ resource class to ‘`size`’. See Customizing Fonts, for details.

`--fullname`
`-f`
  Enable the TTY interface, taking additional debugger commands from standard input and forwarding debugger output on standard output. Current positions are issued in GDB `-fullname` format suitable for debugger front-ends. By default, both the debugger console and source window are disabled. See TTY mode, for a discussion.

  Giving this option is equivalent to setting the DDD ‘`TTYMode`’ resource class to ‘`on`’. See TTY mode, for details.

`--gdb`
  Run GDB as inferior debugger.

  Giving this option is equivalent to setting the DDD ‘`debugger`’ resource to ‘`gdb`’. See Customizing Debugger Interaction, for details.

`--glyphs`
  Display the current execution position and breakpoints as glyphs. See also the `--no-glyphs` option, below.

  Giving this option is equivalent to setting the DDD ‘`displayGlyphs`’ resource to ‘`on`’. See Customizing Source, for details.

`--help`
`-h`
`-?`
  Give a list of frequently used options. Show options of the inferior debugger as well.

  Giving this option is equivalent to setting the DDD ‘`showInvocation`’ resource to ‘`on`’. See Diagnostics, for details.

`--host hostname`
`--host username@hostname`
  Invoke the inferior debugger directly on the remote host hostname. If username is given and the `--login` option is not used, use username as remote user name. See Remote Debugger, for details.

  Giving this option is equivalent to setting the DDD ‘`debuggerHost`’ resource to hostname. See Remote Debugger, for details.

`--jdb`
  Run JDB as inferior debugger.

  Giving this option is equivalent to setting the DDD ‘`debugger`’ resource to ‘`jdb`’. See Customizing Debugger Interaction, for details.

`--ladebug`
  Run Ladebug as inferior debugger.

  Giving this option is equivalent to setting the DDD ‘`debugger`’ resource to ‘`ladebug`’. See Customizing Debugger Interaction, for details.

`--lesstif-hacks`
  Equivalent to `--lesstif-version 999`. Deprecated.

  Giving this option is equivalent to setting the DDD ‘`lessTifVersion`’ resource to `999`. See LessTif, for details.

`--lesstif-version version`
  Enable some hacks to make DDD run properly with LessTif. See LessTif, for a discussion.

  Giving this option is equivalent to setting the DDD ‘`lessTifVersion`’ resource to version. See LessTif, for details.

`--license`
  Print the DDD license on standard output and exit.

  Giving this option is equivalent to setting the DDD ‘`showLicense`’ resource to on. See Diagnostics, for details.

`--login username`
`-l username`
  Use username as remote user name. See Remote Debugger, for details.

  Giving this option is equivalent to setting the DDD ‘`debuggerHostLogin`’ resource to username. See Remote Debugger, for details.

`--maintenance`
  Enable the top-level ‘`Maintenance`’ menu with options for debugging DDD. See Maintenance Menu, for details.

  Giving this option is equivalent to setting the DDD ‘`maintenance`’ resource to on. See Maintenance Menu, for details.

`--manual`
  Print the DDD manual on standard output and exit.

  Giving this option is equivalent to setting the DDD ‘`showManual`’ resource to on. See Diagnostics, for details.

`--news`
  Print the DDD news on standard output and exit.

  Giving this option is equivalent to setting the DDD ‘`showNews`’ resource to on. See Diagnostics, for details.

`--no-button-tips`
  Disable button tips.

  Giving this option is equivalent to setting the DDD ‘`buttonTips`’ resource to ‘`off`’. See Customizing Help, for details.

`--no-data-window`
  Do not open the data window upon start-up.

  Giving this option is equivalent to setting the DDD ‘`openDataWindow`’ resource to ‘`off`’. See Toggling Windows, for details.

`--no-debugger-console`
  Do not open the debugger console upon start-up.

  Giving this option is equivalent to setting the DDD ‘`openDebuggerConsole`’ resource to ‘`off`’. See Toggling Windows, for details.

`--no-disassemble`
  Do not disassemble the source code.

  Giving this option is equivalent to setting the DDD ‘`disassemble`’ resource to ‘`off`’. See Customizing Source, for details.

`--no-exec-window`
  Do not run the debugged program in a specially created execution window; use the debugger console instead. Useful for programs that have little terminal input/output, or for remote debugging. See Using the Execution Window, for details.

  Giving this option is equivalent to setting the DDD ‘`separateExecWindow`’ resource to ‘`off`’. See Customizing the Execution Window, for details.

`--no-glyphs`
  Do not use glyphs; display the current execution position and breakpoints as text characters.

  Giving this option is equivalent to setting the DDD ‘`displayGlyphs`’ resource to ‘`off`’. See Customizing Source, for details.

`--no-lesstif-hacks`
  Equivalent to `--lesstif-version 1000`. Deprecated.

  Giving this option is equivalent to setting the DDD ‘`lessTifVersion`’ resource to `1000`. See LessTif, for details.

`--no-maintenance`
  Do not enable the top-level ‘`Maintenance`’ menu with options for debugging DDD. This is the default. See Maintenance Menu, for details.

  Giving this option is equivalent to setting the DDD ‘`maintenance`’ resource to off. See Maintenance Menu, for details.

`--no-source-window`
  Do not open the source window upon start-up.

  Giving this option is equivalent to setting the DDD ‘`openSourceWindow`’ resource to ‘`off`’. See Toggling Windows, for details.

`--no-value-tips`
  Disable value tips.

  Giving this option is equivalent to setting the DDD ‘`valueTips`’ resource to ‘`off`’. See Value Tips, for details.

`--nw`
  Do not use the X window interface. Start the inferior debugger on the local host.
`--perl`
  Run Perl as inferior debugger.

  Giving this option is equivalent to setting the DDD ‘`debugger`’ resource to ‘`perl`’. See Customizing Debugger Interaction, for details.

`--pydb`
  Run `pydb` as inferior debugger.

  Giving this option is equivalent to setting the DDD ‘`debugger`’ resource to ‘`pydb`’. See Customizing Debugger Interaction, for details.

`--panned-graph-editor`
  Use an Athena panner to scroll the data window. Most people prefer panners on scroll bars, since panners allow two-dimensional scrolling. However, the panner is off by default, since some M*tif implementations do not work well with Athena widgets. See Display Resources, for details; see also `--scrolled-graph-editor`, below.

  Giving this option is equivalent to setting the DDD ‘`pannedGraphEditor`’ resource to ‘`on`’. See Display Resources, for details.

`--play-log log-file`
  Recapitulate a previous DDD session.

                ddd --play-log log-file

  invokes DDD as inferior debugger, simulating the inferior debugger given in log-file (see below). This is useful for debugging DDD.

  Giving this option is equivalent to setting the DDD ‘`playLog`’ resource to ‘`on`’. See Customizing Debugger Interaction, for details.

`--PLAY log-file`
  Simulate an inferior debugger. log-file is a `~/.ddd/log` file as generated by some previous DDD session (see Logging). When a command is entered, scan log-file for this command and re-issue the logged reply; if the command is not found, do nothing. This is used by the `--play` option.
`--rhost hostname`
`--rhost username@hostname`
  Run the inferior debugger interactively on the remote host hostname. If username is given and the `--login` option is not used, use username as remote user name. See Remote Debugger, for details.

  Giving this option is equivalent to setting the DDD ‘`debuggerRHost`’ resource to hostname. See Remote Debugger, for details.

`--scrolled-graph-editor`
  Use M*tif scroll bars to scroll the data window. This is the default in most DDD configurations. See Display Resources, for details; see also `--panned-graph-editor`, above.

  Giving this option is equivalent to setting the DDD ‘`pannedGraphEditor`’ resource to ‘`off`’. See Display Resources, for details.

`--separate-windows`
`--separate`
  Separate the console, source and data windows. See also the `--attach` options, above.

  Giving this option is equivalent to setting the DDD ‘`Separate`’ resource class to ‘`off`’. See Window Layout, for details.

`--session session`
  Load session upon start-up. See Resuming Sessions, for details.

  Giving this option is equivalent to setting the DDD ‘`session`’ resource to session. See Resuming Sessions, for details.

`--source-window`
  Open the source window upon start-up.

  Giving this option is equivalent to setting the DDD ‘`openSourceWindow`’ resource to ‘`on`’. See Toggling Windows, for details.

`--status-at-bottom`
  Place the status line at the bottom of the source window.

  Giving this option is equivalent to setting the DDD ‘`statusAtBottom`’ resource to ‘`on`’. See Window Layout, for details.

`--status-at-top`
  Place the status line at the top of the source window.

  Giving this option is equivalent to setting the DDD ‘`statusAtBottom`’ resource to ‘`off`’. See Window Layout, for details.

`--sync-debugger`
  Do not process X events while the debugger is busy. This may result in slightly better performance on single-processor systems.

  Giving this option is equivalent to setting the DDD ‘`synchronousDebugger`’ resource to ‘`on`’. See Customizing Debugger Interaction, for details.

`--toolbars-at-bottom`
  Place the toolbars at the bottom of the respective window.

  Giving this option is equivalent to setting the DDD ‘`toolbarsAtBottom`’ resource to ‘`on`’. See Window Layout, for details.

`--toolbars-at-top`
  Place the toolbars at the top of the respective window.

  Giving this option is equivalent to setting the DDD ‘`toolbarsAtBottom`’ resource to ‘`off`’. See Window Layout, for details.

`--trace`
  Show the interaction between DDD and the inferior debugger on standard error. This is useful for debugging DDD. If `--trace` is not specified, this information is written into `~/.ddd/log` (`~` stands for your home directory), such that you can also do a post-mortem debugging. See Logging, for details about logging.

  Giving this option is equivalent to setting the DDD ‘`trace`’ resource to on. See Diagnostics, for details.

`--tty`
`-t`
  Enable TTY interface, taking additional debugger commands from standard input and forwarding debugger output on standard output. Current positions are issued in a format readable for humans. By default, the debugger console is disabled.

  Giving this option is equivalent to setting the DDD ‘`ttyMode`’ resource to ‘`on`’. See TTY mode, for details.

`--value-tips`
  Enable value tips.

  Giving this option is equivalent to setting the DDD ‘`valueTips`’ resource to ‘`on`’. See Value Tips, for details.

`--version`
`-v`
  Print the DDD version on standard output and exit.

  Giving this option is equivalent to setting the DDD ‘`showVersion`’ resource to ‘`on`’. See Diagnostics, for details.

`--vsl-library library`
  Load the VSL library library instead of using the DDD built-in library. This is useful for customizing display shapes and fonts.

  Giving this option is equivalent to setting the DDD ‘`vslLibrary`’ resource to library. See VSL Resources, for details.

`--vsl-path path`
  Search VSL libraries in path (a colon-separated directory list).

  Giving this option is equivalent to setting the DDD ‘`vslPath`’ resource to path. See VSL Resources, for details.

`--vsl-help`
  Show a list of further options controlling the VSL interpreter. These options are intended for debugging purposes and are subject to change without further notice.
`--wdb`
  Run WDB as inferior debugger.

  Giving this option is equivalent to setting the DDD ‘`debugger`’ resource to ‘`wdb`’. See Customizing Debugger Interaction, for details.

`--xdb`
  Run XDB as inferior debugger.

  Giving this option is equivalent to setting the DDD ‘`debugger`’ resource to ‘`xdb`’. See Customizing Debugger Interaction, for details.

Next: Inferior Debugger Options, Previous: Options, Up: Invoking

#### 2.1.3 X Options

DDD also understands the following X options. Note that these options only take a single dash `-`.

`-display display`
  Use the X server display. By default, display is taken from the `DISPLAY` environment variable.
`-geometry geometry`
  Specify the initial size and location of the debugger console.
`-iconic`
  Start DDD iconified.
`-name name`
  Give DDD the name name.
`-selectionTimeout timeout`
  Specify the timeout in milliseconds within which two communicating applications must respond to one another for a selection request.
`-title name`
  Give the DDD window the title name.
`-xrm resourcestring`
  Specify a resource name and value to override any defaults.

Next: Multiple Instances, Previous: X Options, Up: Invoking

#### 2.1.4 Inferior Debugger Options

All options that DDD does not recognize are passed to the inferior debugger. This section lists the most useful options of the different inferior debuggers supported by DDD. In case these options do not work as expected, please lookup the appropriate reference.

Next: DBX and Ladebug Options, Up: Inferior Debugger Options

##### 2.1.4.1 GDB Options

These GDB options are useful when using DDD with GDB as inferior debugger. Single dashes `-` instead of double dashes `--` may also be used.

`-b baudrate`
  Set serial port baud rate used for remote debugging.
`--cd dir`
  Change current directory to dir.
`--command file`
  Execute GDB commands from file.
`--core corefile`
  Analyze the core dump corefile.
`--directory dir`
`-d dir`
  Add directory to the path to search for source files.
`--exec execfile`
  Use execfile as the executable.
`--mapped`
  Use mapped symbol files if supported on this system.
`--nx`
`-n`
  Do not read `.gdbinit` file.
`--readnow`
  Fully read symbol files on first access.
`--se file`
  Use file as symbol file and executable file.
`--symbols symfile`
  Read symbols from symfile.

See Invoking GDB, for further options that can be used with GDB.

Next: XDB Options, Previous: GDB Options, Up: Inferior Debugger Options

##### 2.1.4.2 DBX and Ladebug Options

DBX variants differ widely in their options, so we cannot give a list here. Check out the dbx(1) and ladebug(1) manual pages.

Next: JDB Options, Previous: DBX and Ladebug Options, Up: Inferior Debugger Options

##### 2.1.4.3 XDB Options

These XDB options are useful when using DDD with XDB as inferior debugger.

`-d dir`
  Specify dir as an alternate directory where source files are located.
`-P process-id`
  Specify the process ID of an existing process the user wants to debug.
`-l library`
  Pre-load information about the shared library library. `-l ALL` means always pre-load shared library information.
`-S num`
  Set the size of the string cache to num bytes (default is 1024, which is also the minimum).
`-s`
  Enable debugging of shared libraries.

Further options can be found in the xdb(1) manual page.

Next: Bash Options, Previous: XDB Options, Up: Inferior Debugger Options

##### 2.1.4.4 JDB Options

##### JDB as of JDK 1.2

The following JDB options are useful when using DDD with JDB (from JDK 1.2) as inferior debugger.

`-attach address`
  attach to a running virtual machine (VM) at address using standard connector
`-listen address`
  wait for a running VM to connect at address using standard connector
`-listenany`
  wait for a running VM to connect at any available address using standard connector
`-launch`
  launch VM immediately instead of waiting for ‘`run`’ command

These JDB options are forwarded to the debuggee:

`-verbose[:class|gc|jni]`
`-v`
  Turn on verbose mode.
`-Dname=value`
  Set the system property name to value.
`-classpath path`
  List directories in which to look for classes. path is a list of directories separated by colons.
`-X option`
  Non-standard target VM option

##### JDB as of JDK 1.1

The following JDB options are useful when using DDD with JDB (from JDK 1.1) as inferior debugger.

`-host hostname`
  host machine of interpreter to attach to
`-password psswd`
  password of interpreter to attach to (from `-debug`)

These JDB options are forwarded to the debuggee:

`-verbose`
`-v`
  Turn on verbose mode.
`-debug`
  Enable remote Java debugging,
`-noasyncgc`
  Don't allow asynchronous garbage collection.
`-verbosegc`
  Print a message when garbage collection occurs.
`-noclassgc`
  Disable class garbage collection.
`-checksource`
`-cs`
  Check if source is newer when loading classes.
`-ss number`
  Set the maximum native stack size for any thread.
`-oss number`
  Set the maximum Java stack size for any thread.
`-ms number`
  Set the initial Java heap size.
`-mx number`
  Set the maximum Java heap size.
`-Dname=value`
  Set the system property name to value.
`-classpath path`
  List directories in which to look for classes. path is a list of directories separated by colons.
`-prof`
`-prof:file`
  Output profiling data to `./java.prof`. If file is given, write the data to `./file`.
`-verify`
  Verify all classes when read in.
`-verifyremote`
  Verify classes read in over the network (default).
`-noverify`
  Do not verify any class.
`-dbgtrace`
  Print info for debugging JDB.

Further options can be found in the JDB documentation.

Next: GNU Make Options, Previous: JDB Options, Up: Inferior Debugger Options

##### 2.1.4.5 Bash Options

If you have the proper bash installed, the option needed to specify debugging support is `--debugger`. If your bash doesn't understand this option you need to pick up a version of bash that does from http://bashdb.sourceforge.net. Other options can be found from the on-line documentation at http://bashdb.sourceforge.net/bashdb.html

Next: Perl Options, Previous: Bash Options, Up: Inferior Debugger Options

##### 2.1.4.6 GNU Make Options

If you have the proper `make` installed (for now it is probably called `remake`), the option needed to specify debugging support is `--debugger`. You can pick up a debugger-enabled version from http://bashdb.sourceforge.net/remake. Other options can be found from the on-line documentation at http://bashdb.sourceforge.net/remake/mdb.html

Next: PYDB Options, Previous: GNU Make Options, Up: Inferior Debugger Options

##### 2.1.4.7 Perl Options

The most important Perl option to use with DDD is `-w`; it enables several important warnings. For further options, see the perlrun(1) manual page.

Previous: Perl Options, Up: Inferior Debugger Options

##### 2.1.4.8 PYDB Options

An older version of `pydb` used to come with DDD. That is no longer the case. Pick up the newer version of `pydb` from http://bashdb.sourceforge.net/pydb. For a list of useful `pydb` options, check out the `pydb` documentation, http://bashdb.sourceforge.net/pydb/pydb/lib/index.html.

Next: X Warnings, Previous: Inferior Debugger Options, Up: Invoking

#### 2.1.5 Multiple DDD Instances

If you have multiple DDD instances running, they share common preferences and history files. This means that changes applied to one instance may get lost when being overwritten by the other instance. DDD has two means to protect you against unwanted losses. The first means is an automatic reloading of changed options, controlled by the following resource (see Customizing):

— Resource: checkOptions (class CheckOptions)

> Every n seconds, where n is the value of this resource, DDD checks whether the options file has changed. Default is `30`, which means that every 30 seconds, DDD checks for the options file. Setting this resource to `0` disables checking for changed option files.

Normally, automatic reloading of options should already suffice. If you need stronger protection, DDD also provides a warning against multiple instances. This warning is disabled by default, If you want to be warned about multiple DDD invocations sharing the same preferences and history files, enable ‘`Edit Preferences Warn if Multiple DDD Instances are Running`’.

This setting is tied to the following resource (see Customizing):

— Resource: warnIfLocked (class WarnIfLocked)

> Whether to warn if multiple DDD instances are running (‘`on`’) or not (‘`off`’, default).

Previous: Multiple Instances, Up: Invoking

#### 2.1.6 X warnings

If you are bothered by X warnings, you can suppress them by setting ‘`Edit Preferences General Suppress X warnings`’.

This setting is tied to the following resource (see Customizing):

— Resource: suppressWarnings (class SuppressWarnings)

> If ‘`on`’, X warnings are suppressed. This is sometimes useful for executables that were built on a machine with a different X or M*tif configuration. By default, this is ‘`off`’.

Next: Sessions, Previous: Invoking, Up: Invocation

### 2.2 Quitting DDD

To exit DDD, select ‘`File Exit`’. You may also type the `quit` command at the debugger prompt or press <Ctrl+Q>. GDB and XDB also accept the `q` command or an end-of-file character (usually <Ctrl+D>). Closing the last DDD window will also exit DDD.

An interrupt (<ESC> or ‘`Interrupt`’) does not exit from DDD, but rather terminates the action of any debugger command that is in progress and returns to the debugger command level. It is safe to type the interrupt character at any time because the debugger does not allow it to take effect until a time when it is safe.

In case an ordinary interrupt does not succeed, you can also use an abort (<Ctrl+\> or ‘`Abort`’), which sends a `SIGABRT` signal to the inferior debugger. Use this in emergencies only; the inferior debugger may be left inconsistent or even exit after a `SIGABRT` signal.

As a last resort (if DDD hangs, for example), you may also interrupt DDD itself using an interrupt signal (`SIGINT`). This can be done by typing the interrupt character (usually <Ctrl+C>) in the shell DDD was started from, or by using the UNIX ‘`kill`’ command. An interrupt signal interrupts any DDD action; the inferior debugger is interrupted as well. Since this interrupt signal can result in internal inconsistencies, use this as a last resort in emergencies only; save your work as soon as possible and restart DDD.

Next: Remote Debugging, Previous: Quitting, Up: Invocation

### 2.3 Persistent Sessions

If you want to interrupt your current DDD session, you can save the entire the entire DDD state as session on disk and resume later.

Next: Resuming Sessions, Up: Sessions

#### 2.3.1 Saving Sessions

To save a session, select ‘`File Save Session As`’. You will be asked for a symbolic session name session.

If your program is running (see Running), or if you have opened a core file (see Opening Core Dumps), DDD can also include a core file in the session such that the debuggee data will be restored when re-opening it. To get a core file, DDD typically must kill the debuggee. This means that you cannot resume program execution after saving a session. Depending on your architecture, other options for getting a core file may also be available.

Including a core dump is necessary for restoring memory contents and the current execution position. To include a core dump, enable ‘`Include Core Dump`’.

After clicking on ‘`Save`’, the session is saved in `~/.ddd/sessions/session`.

Here's a list of the items whose state is saved in a session:

- The state of the debugged program, as a core file.5
- All breakpoints and watchpoints (see Stopping).
- All signal settings (see Signals).
- All displays (see Displaying Values).6
- All DDD options (see Saving Options).
- All debugger settings (see Debugger Settings).
- All user-defined buttons (see Defining Buttons).
- All user-defined commands (see Defining Commands).
- The positions and sizes of DDD windows.
- The command history (see Command History).

After saving the current state as a session, the session becomes active. This means that DDD state will be saved as session defaults:

- User options will be saved in `~/.ddd/sessions/session/init` instead of `~/.ddd/init`. See Saving Options, for details.
- The DDD command history will be saved in `~/.ddd/sessions/session/history` instead of `~/.ddd/history`. See Command History, for details.

To make the current session inactive, open the default session named ‘`[None]`’. See Resuming Sessions, for details on opening sessions.

Next: Deleting Sessions, Previous: Saving Sessions, Up: Sessions

#### 2.3.2 Resuming Sessions

To resume a previously saved session, select ‘`File Open Session`’ and choose a session name from the list. After clicking on ‘`Open`’, the entire DDD state will be restored from the given session.

The session named ‘`[None]`’ is the default session which is active when starting DDD. To save options for default sessions, choose the default session before exiting DDD. See Saving Options, for details.

If a the restored session includes a core dump, the program being debugged will be in the same state at the time the session was saved; in particular, you can examine the program data. However, you will not be able to resume program execution since the process and its environment (open files, resources, etc.) no longer exist. However, you can restart the program, re-using the restored breakpoints and data displays.

Opening sessions also restores command definitions, buttons, display shortcuts and the source tab width. This way, you can maintain a different set of definitions for each session.

You can also specify a session to open when starting DDD. To invoke DDD with a session session, use

         ddd --session session

There is also a shortcut that opens the session session and invokes the inferior debugger on an executable named session (in case session cannot be opened):

         ddd =session

There is no need to give further command-line options when restarting a session, as they will be overridden by the options saved in the session.

You can also use an X session manager such as `xsm` to save and restore DDD sessions.7 When being shut down by a session manager, DDD saves its state under the name specified by the session manager; resuming the X session makes DDD reload its saved state.

Next: Customizing Sessions, Previous: Resuming Sessions, Up: Sessions

#### 2.3.3 Deleting Sessions

To delete sessions that are no longer needed, select ‘`File Open Session`’ or ‘`File Save Session`’. Select the sessions you want to delete and click on ‘`Delete`’.

The default session ‘`[None]`’ cannot be deleted.

Previous: Deleting Sessions, Up: Sessions

#### 2.3.4 Customizing Sessions

You can change the place where DDD saves its sessions by setting the environment variable `DDD_SESSIONS` to the name of a directory. Default is `~/.ddd/sessions/`.

Where applicable, DDD supports a `gcore` command to obtain core files of the running program. You can enter its path via ‘`Edit Preferences Helpers Get Core File`’. Leave the value empty if you have no `gcore` or similar command.

This setting is tied to the following resource (see Customizing):

— Resource: getCoreCommand (class GetCoreCommand)

> A command to get a core dump of a running process (typically, `gcore`) ‘`@FILE@`’ is replaced by the base name of the file to create; ‘`@PID@`’ is replaced by the process id. The output must be written to ‘`@FILE@.@PID@`’.

> Leave the value empty if you have no `gcore` or similar command.

Next: Customizing Debugger Interaction, Previous: Sessions, Up: Invocation

### 2.4 Remote Debugging

You can have each of DDD, the inferior debugger, and the debugged program run on different machines.

Next: Remote Debugger, Up: Remote Debugging

#### 2.4.1 Running DDD on a Remote Host

You can run DDD on a remote host, using your current host as X display. On the remote host, invoke DDD as

         ddd -display display

where display is the name of the X server to connect to (for instance, ‘`hostname:0.0`’, where hostname is your host).

Instead of specifying `-display display`, you can also set the `DISPLAY` environment variable to display.

Next: Remote Program, Previous: Remote Host, Up: Remote Debugging

#### 2.4.2 Using DDD with a Remote Inferior Debugger

In order to run the inferior debugger on a remote host, you need ‘`remsh`’ (called ‘`rsh`’ on BSD systems) access on the remote host.

To run the debugger on a remote host hostname, invoke DDD as

         ddd --host hostname remote-program

If your remote username differs from the local username, use

         ddd --host hostname --login username remote-program

or

         ddd --host username@hostname remote-program

instead.

There are a few caveats in remote mode:

- The remote debugger is started in your remote home directory. Hence, you must specify an absolute path name for remote-program (or a path name relative to your remote home directory). Same applies to remote core files. Also, be sure to specify a remote process id when debugging a running program.
- The remote debugger is started non-interactively. Some DBX versions have trouble with this. If you do not get a prompt from the remote debugger, use the `--rhost` option instead of `--host`. This will invoke the remote debugger via an interactive shell on the remote host, which may lead to better results.

  Note: using `--rhost`, DDD invokes the inferior debugger as soon as a shell prompt appears. The first output on the remote host ending in a space character or ‘`>`’ and not followed by a newline is assumed to be a shell prompt. If necessary, adjust your shell prompt on the remote host.

- To run the remote program, DDD invokes an ‘`xterm`’ terminal emulator on the remote host, giving your current ‘`DISPLAY`’ environment variable as address. If the remote host cannot invoke ‘`xterm`’, or does not have access to your X display, start DDD with the `--no-exec-window` option. The program input/output will then go through the DDD debugger console.
- In remote mode, all sources are loaded from the remote host; file dialogs scan remote directories. This may result in somewhat slower operation than normal.
- To help you find problems due to remote execution, run DDD with the `--trace` option. This prints the shell commands issued by DDD on standard error.

See Customizing Remote Debugging, for customizing remote mode.

Up: Remote Debugger

##### 2.4.2.1 Customizing Remote Debugging

When having the inferior debugger run on a remote host (see Remote Debugging), all commands to access the inferior debugger as well as its files must be run remotely. This is controlled by the following resources (see Customizing):

— Resource: rshCommand (class RshCommand)

> The remote shell command to invoke TTY-based commands on remote hosts. Usually, `remsh`, `rsh`, `ssh`, or `on`.

— Resource: listCoreCommand (class listCoreCommand)

> The command to list all core files on the remote host. The string ‘`@MASK@`’ is replaced by a file filter. The default setting is:

>               Ddd*listCoreCommand: \
>               file @MASK@ | grep '.*:.*core.*' | cut -d: -f1

— Resource: listDirCommand (class listDirCommand)

> The command to list all directories on the remote host. The string ‘`@MASK@`’ is replaced by a file filter. The default setting is:

>               Ddd*listDirCommand: \
>               file @MASK@ | grep '.*:.*directory.*' | cut -d: -f1

— Resource: listExecCommand (class listExecCommand)

> The command to list all executable files on the remote host. The string ‘`@MASK@`’ is replaced by a file filter. The default setting is:

>               Ddd*listExecCommand: \
>               file @MASK@ | grep '.*:.*exec.*' \
>                 | grep -v  '.*:.*script.*' \
>                 | cut -d: -f1 | grep -v '.*\.o$'

— Resource: listSourceCommand (class listSourceCommand)

> The command to list all source files on the remote host. The string ‘`@MASK@`’ is replaced by a file filter. The default setting is:

>               Ddd*listSourceCommand: \
>               file @MASK@ | grep '.*:.*text.*' | cut -d: -f1

Previous: Remote Debugger, Up: Remote Debugging

#### 2.4.3 Debugging a Remote Program

The GDB debugger allows you to run the debugged program on a remote machine (called remote target), while GDB runs on the local machine.

See Remote Debugging, for details. Basically, the following steps are required:

- Transfer the executable to the remote target.
- Start `gdbserver` on the remote target.
- Start DDD using GDB on the local machine, and load the same executable using the GDB `file` command.
- Attach to the remote ‘`gdbserver`’ using the GDB `target remote` command.

The local `.gdbinit` file is useful for setting up directory search paths, etc.

Of course, you can also combine DDD remote mode and GDB remote mode, running DDD, GDB, and the debugged program each on a different machine.

Previous: Remote Debugging, Up: Invocation

### 2.5 Customizing Interaction with the Inferior Debugger

These settings control the interaction of DDD with its inferior debugger.

Next: Debugger Initialization, Up: Customizing Debugger Interaction

#### 2.5.1 Invoking an Inferior Debugger

To choose the default inferior debugger, select ‘`Edit Preferences Startup Debugger Type`’. You can

- have DDD determine the appropriate inferior debugger automatically from its command-line arguments. Set ‘`Determine Automatically from Arguments`’ to enable.
- have DDD start the debugger of your choice, as specified in ‘`Debugger Type`’.

The following DDD resources control the invocation of the inferior debugger (see Customizing).

— Resource: autoDebugger (class AutoDebugger)

> If this is ‘`on`’ (default), DDD will attempt to determine the debugger type from its arguments, possibly overriding the ‘`debugger`’ resource (see below). If this is ‘`off`’, DDD will invoke the debugger specified by the ‘`debugger`’ resource regardless of DDD arguments.

— Resource: debugger (class Debugger)

> The type of the inferior debugger to invoke (‘`bash`’ ‘`dbx`’, ‘`gdb`’, ‘`jdb`’, ‘`ladebug`’, ‘`make`’, ‘`perl`’, ‘`pydb`’, or ‘`xdb`’).

> This resource is usually set through the `--bash`, `--dbx`, `--gdb`, `--jdb`, `--ladebug`, `--make`, `--perl`, `--pydb`, and `--xdb`, options; See Options, for details.

— Resource: debuggerCommand (class DebuggerCommand)

> The name under which the inferior debugger is to be invoked. If this string is empty (default), the debugger type (‘`debugger`’ resource) is used.

> This resource is usually set through the `--debugger` option; See Options, for details.

Next: Debugger Communication, Previous: Debugger Invocation, Up: Customizing Debugger Interaction

#### 2.5.2 Initializing the Inferior Debugger

DDD uses a number of resources to initialize the inferior debugger (see Customizing).

Next: DBX Initialization, Up: Debugger Initialization

##### 2.5.2.1 Bash Initialization

— Resource: bashInitCommands (class InitCommands)

> This string contains a list of newline-separated commands that are initially sent to the Bash debugger. By default, it is empty.

> This resource may be used to customize the Bash debugger.

— Resource: bash (class Settings)

> This string contains a list of newline-separated commands that are also initially sent to the Bash debugger. By default, it is empty.

> This resource is used by DDD to save and restore Bash debugger settings.

Next: GDB Initialization, Previous: Bash Initialization, Up: Debugger Initialization

##### 2.5.2.2 DBX Initialization

— Resource: dbxInitCommands (class InitCommands)

> This string contains a list of newline-separated commands that are initially sent to DBX. By default, it is empty.

> Do not use this resource to customize DBX; instead, use a personal `~/.dbxinit` or `~/.dbxrc` file. See your DBX documentation for details.

— Resource: dbxSettings (class Settings)

> This string contains a list of newline-separated commands that are also initially sent to DBX. By default, it is empty.

Next: JDB Initialization, Previous: DBX Initialization, Up: Debugger Initialization

##### 2.5.2.3 GDB Initialization

— Resource: gdbInitCommands (class InitCommands)

> This string contains a list of newline-separated commands that are initially sent to GDB. As a side-effect, all settings specified in this resource are considered fixed and cannot be changed through the GDB settings panel, unless preceded by white space. By default, the ‘`gdbInitCommands`’ resource contains some settings vital to DDD:

>                 Ddd*gdbInitCommands: \
>                 set height 0\n\
>                 set width 0\n\
>                  set verbose off\n\
>                 set prompt (gdb) \n

> While the ‘`set height`’, ‘`set width`’, and ‘`set prompt`’ settings are fixed, the ‘`set verbose`’ settings can be changed through the GDB settings panel (although being reset upon each new DDD invocation).

> Do not use this resource to customize GDB; instead, use a personal `~/.gdbinit` file. See your GDB documentation for details.

— Resource: gdbSettings (class Settings)

> This string contains a list of newline-separated commands that are also initially sent to GDB. Its default value is

>                 Ddd*gdbSettings: \
>                 set print asm-demangle on\n

> This resource is used to save and restore the debugger settings.

— Resource: sourceInitCommands (class SourceInitCommands)

> If ‘`on`’ (default), DDD writes all GDB initialization commands into a temporary file and makes GDB read this file, rather than sending each initialization command separately. This results in faster startup (especially if you have several user-defined commands). If ‘`off`’, DDD makes GDB process each command separately.

Next: GNU Make Initialization, Previous: GDB Initialization, Up: Debugger Initialization

##### 2.5.2.4 JDB Initialization

— Resource: jdbInitCommands (class InitCommands)

> This string contains a list of newline-separated commands that are initially sent to JDB. This resource may be used to customize JDB. By default, it is empty.

— Resource: jdbSettings (class Settings)

> This string contains a list of newline-separated commands that are also initially sent to JDB. By default, it is empty.

> This resource is used by DDD to save and restore JDB settings.

Next: Perl Initialization, Previous: JDB Initialization, Up: Debugger Initialization

##### 2.5.2.5 GNU Make Initialization

— Resource: makeInitCommands (class InitCommands)

> This string contains a list of newline-separated commands that are initially sent to the Bash debugger. By default, it is empty.

> This resource may be used to customize GNU Make debugging.

— Resource: bash (class Settings)

> This string contains a list of newline-separated commands that are also initially sent to the GNU Make debugger. By default, it is empty.

> This resource is used by DDD to save and restore GNU Make debugger settings.

Next: PYDB Initialization, Previous: GNU Make Initialization, Up: Debugger Initialization

##### 2.5.2.6 Perl Initialization

— Resource: perlInitCommands (class InitCommands)

> This string contains a list of newline-separated commands that are initially sent to the Perl debugger. By default, it is empty.

> This resource may be used to customize the Perl debugger.

— Resource: perlSettings (class Settings)

> This string contains a list of newline-separated commands that are also initially sent to the Perl debugger. By default, it is empty.

> This resource is used by DDD to save and restore Perl debugger settings.

Next: XDB Initialization, Previous: Perl Initialization, Up: Debugger Initialization

##### 2.5.2.7 PYDB Initialization

— Resource: pydbInitCommands (class InitCommands)

> This string contains a list of newline-separated commands that are initially sent to `pydb`. By default, it is empty.

> This resource may be used to customize `pydb`.

— Resource: pydbSettings (class Settings)

> This string contains a list of newline-separated commands that are also initially sent to `pydb`. By default, it is empty.

> This resource is used by DDD to save and restore `pydb` settings.

Next: Finding a Place to Start, Previous: PYDB Initialization, Up: Debugger Initialization

##### 2.5.2.8 XDB Initialization

— Resource: xdbInitCommands (class InitCommands)

> This string contains a list of newline-separated commands that are initially sent to XDB. By default, it is empty.

> Do not use this resource to customize DBX; instead, use a personal `~/.xdbrc` file. See your XDB documentation for details.

— Resource: xdbSettings (class Settings)

> This string contains a list of newline-separated commands that are also initially sent to XDB. By default, it is empty.

Next: Opening the Selection, Previous: XDB Initialization, Up: Debugger Initialization

##### 2.5.2.9 Finding a Place to Start

— Resource: initSymbols (class InitSymbols)

> When loading an executable, DDD queries the inferior debugger for the initial source location—typically the `main` function. If this location is not found, DDD tries other symbols from this newline-separated list. The default value makes DDD look for a variety of main functions (especially FORTRAN main functions):

>               main\n\
>               MAIN\n\
>               main_\n\
>               MAIN_\n\
>               main__\n\
>               MAIN__\n\
>               _main\n\
>               _MAIN\n\
>               __main\n\
>               __MAIN

Previous: Finding a Place to Start, Up: Debugger Initialization

##### 2.5.2.10 Opening the Selection

— Resource: openSelection (class OpenSelection)

> If this is ‘`on`’, DDD invoked without argument checks whether the current selection or clipboard contains the file name or URL of an executable program. If this is so, DDD will automatically open this program for debugging. If this resource is ‘`off`’ (default), DDD invoked without arguments will always start without a debugged program.

Previous: Debugger Initialization, Up: Customizing Debugger Interaction

#### 2.5.3 Communication with the Inferior Debugger

The following resources control the communication with the inferior debugger.

— Resource: blockTTYInput (class BlockTTYInput)

> Whether DDD should block when reading data from the inferior debugger via the pseudo-tty interface. Most UNIX systems except GNU/Linux require this; set it to ‘`on`’. On GNU/Linux, set it to ‘`off`’. The value ‘`auto`’ (default) will always select the “best” choice (that is, the best choice known to the DDD developers).

— Resource: bufferGDBOutput (class BufferGDBOutput)

> If this is ‘`on`’, all output from the inferior debugger is buffered until a debugger prompt appears. This makes it easier for DDD to parse the output, but has the drawback that interaction with a running debuggee in the debugger console is not possible. If ‘`off`’, output is shown as soon as it arrives, enabling interaction, but making it harder for DDD to parse the output. If ‘`auto`’ (default), output is buffered if and only if the execution window is open, which redirects debuggee output and thus enables interaction. See Using the Execution Window, for details.

— Resource: contInterruptDelay (class InterruptDelay)

> The time (in ms) to wait before automatically interrupting a ‘`cont`’ command. DDD cannot interrupt a ‘`cont`’ command immediately, because this may disturb the status change of the process. Default is `200`.

— Resource: displayTimeout (class DisplayTimeout)

> The time (in ms) to wait for the inferior debugger to finish a partial display information. Default is `2000`.

— Resource: positionTimeout (class PositionTimeout)

> The time (in ms) to wait for the inferior debugger to finish a partial position information. Default is `500`.

— Resource: questionTimeout (class QuestionTimeout)

> The time (in seconds) to wait for the inferior debugger to reply. Default is `10`.

— Resource: runInterruptDelay (class InterruptDelay)

> The time (in ms) to wait before automatically interrupting a ‘`run`’ command. DDD cannot interrupt a ‘`cont`’ command immediately, because this may disturb process creation. Default is `2000`.

— Resource: stopAndContinue (class StopAndContinue)

> If ‘`on`’ (default), debugger commands interrupt program execution, resuming execution after the command has completed. This only happens if the last debugger command was either a ‘`run`’ or a ‘`continue`’ command. If ‘`off`’, debugger commands do not interrupt program execution.

— Resource: synchronousDebugger (class SynchronousDebugger)

> If ‘`on`’, X events are not processed while the debugger is busy. This may result in slightly better performance on single-processor systems. See Options, for the `--sync-debugger` option.

— Resource: terminateOnEOF (class TerminateOnEOF)

> If ‘`on`’, DDD terminates the inferior debugger when DDD detects an EOF condition (that is, as soon as the inferior debugger closes its output channel). This was the default behavior in DDD 2.x and earlier. If ‘`off`’ (default), DDD takes no special action.

— Resource: useTTYCommand (class UseTTYCommand)

> If ‘`on`’, use the GDB `tty` command for redirecting input/output to the separate execution window. If ‘`off`’, use explicit redirection through shell redirection operators ‘`<`’ and ‘`>`’. The default is ‘`off`’ (explicit redirection), since on some systems, the `tty` command does not work properly on some GDB versions.

Next: Navigating, Previous: Invocation, Up: Top

## 3 The DDD Windows

DDD is composed of three main windows. From top to bottom, we have:

- The Data Window shows the current data of the debugged program. See Displaying Values, for details.
- The Source Window shows the current source code of the debugged program. See Navigating, for details.
- The Debugger Console accepts debugger commands and shows debugger messages. See Commands, for details.

Besides these three main windows, there are some other optional windows:

- The Command Tool offers buttons for frequently used commands. It is usually placed on the source window. See Command Tool, for details.
- The Machine Code Window shows the current machine code. It is usually placed beneath the current source. See Machine Code, for details.
- The Execution Window shows the input and output of the debugged program. See Using the Execution Window, for details.

Next: Tool Bar, Up: Windows

### 3.1 The Menu Bar

The DDD Menu Bar gives you access to all DDD functions.

`File`
  Perform file-related operations such as selecting programs, processes, and sessions, printing graphs, recompiling, as well as exiting DDD.
`Edit`
  Perform standard editing operations, such as cutting, copying, pasting, and killing selected text. Also allows editing DDD options and preferences.
`View`
  Allows accessing the individual DDD windows.
`Program`
  Perform operations related to the program being debugged, such as starting and stopping the program.
`Commands`
  Perform operations related to DDD commands, such as accessing the command history or defining new commands.
`Status`
  Examine the program status, such as the stack traces, registers, or threads.
`Source`
  Perform source-related operations such as looking up items or editing breakpoints.
`Data`
  Perform data-related operations such as editing displays or layouting the display graph.
`Maintenance`
  Perform operations that are useful for debugging DDD. By default, this menu is disabled.
`Help`
  Give help on DDD usage.

There are two ways of selecting an item from a pull-down menu:

- Select an item in the menu bar by moving the cursor over it and click mouse button 1. Then move the cursor over the menu item you want to choose and click left again.
- Select an item in the menu bar by moving the cursor over it and click and hold mouse button 1. With the mouse button depressed, move the cursor over the menu item you want, then release it to make your selection.

The menus can also be torn off (i.e. turned into a persistent window) by selecting the dashed line at the top.

If a command in the pull-down menu is not applicable in a given situation, the command is disabled and its name appears faded. You cannot invoke items that are faded. For example, many commands on the ‘`Edit`’ menu appear faded until you select text on which they are to operate; after you select a block of text, edit commands are enabled.

Next: Edit Menu, Up: Menu Bar

#### 3.1.1 The File Menu

The ‘`File`’ menu contains file-related operations such as selecting programs, processes, and sessions, printing graphs, recompiling, as well as exiting DDD.

`Open Program`
`Open Class`
  Open a program or class to be debugged (<Ctrl+O>). See Opening Programs, for details.
`Open Recent`
  Re-open a recently opened program to be debugged. See Opening Programs, for details.
`Open Core Dump`
  Open a core dump for the currently debugged program. See Opening Core Dumps, for details.
`Open Source`
  Open a source file of the currently debugged program. See Opening Source Files, for details.
`Open Session`
  Resume a previously saved DDD session (<Ctrl+N>). See Resuming Sessions, for details.
`Save Session As`
  Save the current DDD session such that you can resume it later (<Ctrl+S>). See Saving Sessions, for details.
`Attach to Process`
  Attach to a running process of the debugged program. See Attaching to a Process, for details.
`Detach Process`
  Detach from the running process. See Attaching to a Process, for details.
`Print Graph`
  Print the current graph on a printer. See Printing the Graph, for details.
`Change Directory`
  Change the working directory of your program. See Working Directory, for details.
`Make`
  Run the `make` program (<Ctrl+M>). See Recompiling, for details.
`Close`
  Close this DDD window (<Ctrl+W>). See Quitting, for details.
`Restart`
  Restart DDD.
`Exit`
  Exit DDD (<Ctrl+Q>). See Quitting, for details.

Next: View Menu, Previous: File Menu, Up: Menu Bar

#### 3.1.2 The Edit Menu

The ‘`Edit`’ menu contains standard editing operations, such as cutting, copying, pasting, and killing selected text. Also allows editing DDD options and preferences.

`Undo`
  Undo the most recent action (<Ctrl+Z>). Almost all commands can be undone this way. See Undo and Redo, for details.
`Redo`
  Redo the action most recently undone (<Ctrl+Y>). Every command undone can be redone this way. See Undo and Redo, for details.
`Cut`
  Removes the selected text block from the current text area and makes it the X clipboard selection (<Ctrl+X> or <Shift+Del>; See Customizing the Edit Menu, for details). Before executing this command, you have to select a region in a text area—either with the mouse or with the usual text selection keys.

  This item can also be applied to displays (see Deleting Displays).

`Copy`
  Makes a selected text block the X clipboard selection (<Ctrl+C> or <Ctrl+Ins>; See Customizing the Edit Menu, for details). You can select text by selecting a text region with the usual text selection keys or with the mouse. See Customizing the Edit Menu, for changing the default accelerator.

  This item can also be applied to displays (see Deleting Displays).

`Paste`
  Inserts the current value of the X clipboard selection in the most recently selected text area (<Ctrl+V> or <Shift+Ins>; See Customizing the Edit Menu, for details). You can paste in text you have placed in the clipboard using ‘`Copy`’ or ‘`Cut`’. You can also use ‘`Paste`’ to insert text that was pasted into the clipboard from other applications.
`Clear`
  Clears the most recently selected text area (<Ctrl+U>).
`Delete`
  Removes the selected text block from the most recently selected text area, but does not make it the X clipboard selection.

  This item can also be applied to displays (see Deleting Displays).

`Select All`
  Selects all characters from the most recently selected text area (<Ctrl+A> or or <Ctrl+Shift+A>; see Customizing the Edit Menu, for details).
`Preferences`
  Allows you to customize DDD interactively. See Customizing, for details.
`Debugger Settings`
  Allows you to customize the inferior debugger. See Debugger Settings, for details.
`Save Options`
  If set, all preferences and settings will be saved for the next DDD invocation. See Saving Options, for details.

Next: Program Menu, Previous: Edit Menu, Up: Menu Bar

#### 3.1.3 The View Menu

The ‘`View`’ menu allows accessing the individual DDD windows.

`Command Tool`
  Open and recenter the command tool (<Alt+8>). See Command Tool, for details.
`Execution Window`
  Open the separate execution window (<Alt+9>). See Using the Execution Window, for details.
`Debugger Console`
  Open the debugger console (<Alt+1>). See Commands, for details.
`Source Window`
  Open the source window (<Alt+2>). See Navigating, for details.
`Data Window`
  Open the data window (<Alt+3>). See Displaying Values, for details.
`Machine Code Window`
  Show machine code (<Alt+4>). See Machine Code, for details.

Next: Commands Menu, Previous: View Menu, Up: Menu Bar

#### 3.1.4 The Program Menu

The ‘`Program`’ menu performs operations related to the program being debugged, such as starting and stopping the program.

Most of these operations are also found on the command tool (see Command Tool).

`Run`
  Start program execution, prompting for program arguments (<F2>). See Starting Program Execution, for details.
`Run Again`
  Start program execution with the most recently used arguments (<F3>). See Starting Program Execution, for details.
`Run in Execution Window`
  If enabled, start next program execution in separate execution window. See Using the Execution Window, for details.
`Step`
  Continue running your program until control reaches a different source line, then stop it and return control to DDD (<F5>). See Resuming Execution, for details.
`Step Instruction`
  Execute one machine instruction, then stop and return to DDD (<Shift+F5>). See Machine Code Execution, for details.
`Next`
  Continue to the next source line in the current (innermost) stack frame (<F6>). This is similar to ‘`Step`’, but function calls that appear within the line of code are executed without stopping. See Resuming Execution, for details.
`Next Instruction`
  Execute one machine instruction, but if it is a function call, proceed until the function returns (<Shift+F6>). See Machine Code Execution, for details.
`Until`
  Continue running until a source line past the current line, in the current stack frame, is reached (<F7>). See Resuming Execution, for details.
`Finish`
  Continue running until just after function in the selected stack frame returns (<F8>). Print the returned value (if any). See Resuming Execution, for details.
`Continue`
  Resume program execution, at the address where your program last stopped (<F9>); any breakpoints set at that address are bypassed. See Resuming Execution, for details.
`Continue Without Signal`
  Continue execution without giving a signal (<Shift+F9>). This is useful when your program stopped on account of a signal and would ordinary see the signal when resumed with ‘`Continue`’. See Signals, for details.
`Kill`
  Kill the process of the debugged program (<F4>). See Killing the Program, for details.
`Interrupt`
  Interrupt program execution (<Esc> or <Ctrl+C>; see Customizing the Edit Menu, for details). This is equivalent to sending an interrupt signal to the process. See Interrupting, for details.
`Abort`
  Abort program execution (and maybe debugger execution, too; <Ctrl+\>). This is equivalent to sending a `SIGABRT` signal to the process. See Quitting, for details.

Next: Status Menu, Previous: Program Menu, Up: Menu Bar

#### 3.1.5 The Commands Menu

The ‘`Commands`’ menu performs operations related to DDD commands, such as accessing the command history or defining new commands.

Most of these items are not meant to be actually executed via the menu; instead, they serve as reminder for the equivalent keyboard commands.

`Command History`
  View the command history. See Command History, for details.
`Previous`
  Show the previous command from the command history (<Up>). See Command History, for details.
`Next`
  Show the next command from the command history (<Down>). See Command History, for details.
`Find Backward`
  Do an incremental search backward through the command history (<Ctrl+B>). See Command History, for details.
`Find Forward`
  Do an incremental search forward through the command history (<Ctrl+F>). See Command History, for details.
`Quit Search`
  Quit incremental search through the command history (<Esc>). See Command History, for details.
`Complete`
  Complete the current command in the debugger console (<Tab>). See Entering Commands, for details.
`Apply`
  Apply the current command in the debugger console (<Apply>). See Entering Commands, for details.
`Clear Line`
  Clear the current command line in the debugger console (<Ctrl+U>). See Entering Commands, for details.
`Clear Window`
  Clear the debugger console (<Shift+Ctrl+U>). See Entering Commands, for details.
`Define Command`
  Define a new debugger command. See Defining Commands, for details.
`Edit Buttons`
  Customize DDD buttons. See Defining Buttons, for details.

Next: Source Menu, Previous: Commands Menu, Up: Menu Bar

#### 3.1.6 The Status Menu

The ‘`Status`’ menu lets you examine the program status, such as the stack traces, registers, or threads.

`Backtrace`
  View the current backtrace. See Backtraces, for a discussion.
`Registers`
  View the current register contents. See Registers, for details.
`Threads`
  View the current threads. See Threads, for details.
`Signals`
  View and edit the current signal handling. See Signals, for details.
`Up`
  Select the stack frame (i.e. the function) that called this one (<Ctrl+Up>). This advances toward the outermost frame, to higher frame numbers, to frames that have existed longer. See Stack, for details.
`Down`
  Select the stack frame (i.e. the function) that was called by this one (<Ctrl+Down>). This advances toward the innermost frame, to lower frame numbers, to frames that were created more recently. See Stack, for details.

Next: Data Menu, Previous: Status Menu, Up: Menu Bar

#### 3.1.7 The Source Menu

The ‘`Source`’ menu performs source-related operations such as looking up items or editing breakpoints.

`Breakpoints`
  Edit all Breakpoints. See Editing all Breakpoints, for details.
`Lookup ()`
  Look up the argument ‘`()`’ in the source code (<Ctrl+/>). See Looking up Definitions, for details.
`Find >> ()`
  Look up the next occurrence of the argument ‘`()`’ in the current source code (<Ctrl+.>). See Textual Search, for details.
`Find << ()`
  Look up the previous occurrence of the argument ‘`()`’ in the current source code (<Ctrl+,>). See Textual Search, for details.
`Find Words Only`
  If enabled, find only complete words (<Alt+W>). See Textual Search, for details.
`Find Case Sensitive`
  If enabled, find is case-sensitive (<Alt+I>). See Textual Search, for details.
`Display Line Numbers`
  If enabled, prefix source lines with their line number (<Alt+N>). See Customizing Source, for details.
`Display Machine Code`
  If enabled, show machine code (<Alt+4>). See Machine Code, for details.
`Edit Source`
  Invoke an editor for the current source file (<Shift+Ctrl+V>). See Editing Source Code, for details.
`Reload Source`
  Reload the current source file (<Shift+Ctrl+L>). See Editing Source Code, for details.

Next: Maintenance Menu, Previous: Source Menu, Up: Menu Bar

#### 3.1.8 The Data Menu

The ‘`Data`’ menu performs data-related operations such as editing displays or layouting the display graph.

`Displays`
  Invoke the Display Editor. See Editing all Displays, for details.
`Watchpoints`
  Edit all Watchpoints. See Editing all Watchpoints, for details.
`Memory`
  View a memory dump. See Examining Memory, for details.
`Print ()`
  Print the value of ‘`()`’ in the debugger console (<Ctrl+=>). See Printing Values, for details.
`Display ()`
  Display the value of ‘`()`’ in the data window (<Ctrl+->). See Displaying Values, for details.
`Detect Aliases`
  If enabled, detect shared data structures (<Alt+A>). See Shared Structures, for a discussion.
`Display Local Variables`
  Show all local variables in a display (<Alt+L>). See Displaying Local Variables, for details.
`Display Arguments`
  Show all arguments of the current function in a display (<Alt+U>). See Displaying Local Variables, for details.
`Status Displays`
  Show current debugging information in a display. See Displaying Program Status, for details.
`Align on Grid`
  Align all displays on the grid (<Alt+G>). See Aligning Displays, for a discussion.
`Rotate Graph`
  Rotate the graph by 90 degrees (<Alt+R>). See Rotating the Graph, for details.
`Layout Graph`
  Layout the graph (<Alt+Y>). See Layouting the Graph, for details.
`Refresh`
  Update all values in the data window (<Ctrl+L>). See Refreshing the Data Window, for details.

Next: Help Menu, Previous: Data Menu, Up: Menu Bar

#### 3.1.9 The Maintenance Menu

The ‘`Maintenance`’ menu performs operations that are useful for debugging DDD.

By default, this menu is disabled; it is enabled by specifically requesting it at DDD invocation (via the `--maintenance` option; see Options). It is also enabled when DDD gets a fatal signal.

`Debug DDD`
  Invoke a debugger (typically, GDB) and attach it to this DDD process (<F12>). This is useful only if you are a DDD maintainer.
`Dump Core Now`
  Make this DDD process dump core. This can also be achieved by sending DDD a `SIGUSR1` signal.
`Tic Tac Toe`
  Invoke a Tic Tac Toe game. You must try to get three stop signs in a row, while preventing DDD from doing so with its skulls. Click on ‘`New Game`’ to restart.
`When DDD Crashes`
  Select what to do when DDD gets a fatal signal.
  `Debug DDD`
    Invoke a debugger on the DDD core dump when DDD crashes. This is useful only if you are a DDD maintainer.
  `Dump Core`
    Just dump core when DDD crashes; don't invoke a debugger. This is the default setting, as the core dump may contain important information required for debugging DDD.
  `Do Nothing`
    Do not dump core or invoke a debugger when DDD crashes.
`Remove Menu`
  Make this menu inaccessible again.

Next: Customizing the Menu Bar, Previous: Maintenance Menu, Up: Menu Bar

#### 3.1.10 The Help Menu

The ‘`Help`’ menu gives help on DDD usage. See Getting Help, for a discussion on how to get help within DDD.

`Overview`
  Explains the most important concepts of DDD help.
`On Item`
  Lets you click on an item to get help on it.
`On Window`
  Gives you help on this DDD window.
`What Now?`
  Gives a hint on what to do next.
`Tip of the Day`
  Shows the current tip of the day.
`DDD Reference`
  Shows the DDD Manual.
`DDD News`
  Shows what's new in this DDD release.
`Debugger Reference`
  Shows the on-line documentation for the inferior debugger.
`DDD License`
  Shows the DDD License (see License).
`DDD WWW Page`
  Invokes a WWW browser for the DDD WWW page.
`About DDD`
  Shows version and copyright information.

Previous: Help Menu, Up: Menu Bar

#### 3.1.11 Customizing the Menu Bar

The Menu Bar can be customized in various ways (see Customizing).

Next: Customizing the Edit Menu, Up: Customizing the Menu Bar

##### 3.1.11.1 Auto-Raise Menus

You can cause pull-down menus to be raised automatically.

— Resource: autoRaiseMenu (class AutoRaiseMenu)

> If ‘`on`’ (default), DDD will always keep the pull down menu on top of the DDD main window. If this setting interferes with your window manager, or if your window manager does not auto-raise windows, set this resource to ‘`off`’.

— Resource: autoRaiseMenuDelay (class AutoRaiseMenuDelay)

> The time (in ms) during which an initial auto-raised window blocks further auto-raises. This is done to prevent two overlapping auto-raised windows from entering an auto-raise loop. Default is `100`.

Previous: Auto-Raise Menus, Up: Customizing the Menu Bar

##### 3.1.11.2 Customizing the Edit Menu

In the Menu Bar, the ‘`Edit`’ Menu can be customized in various ways. Use ‘`Edit Preferences Startup`’ to customize these keys.

The <Ctrl+C> key can be bound to different actions, each in accordance with a specific style guide.

`Copy`
  This setting binds <Ctrl+C> to the Copy operation, as specified by the KDE style guide. In this setting, use <ESC> to interrupt the debuggee.
`Interrupt`

This (default) setting binds <Ctrl+C> to the Interrupt operation, as used in several UNIX command-line programs. In this setting, use <Ctrl+Ins> to copy text to the clipboard.

The <Ctrl+A> key can be bound to different actions, too.

`Select All`
  This (default) setting binds <Ctrl+A> to the ‘`Select All`’ operation, as specified by the KDE style guide. In this setting, use <Home> to move the cursor to the beginning of a line.
`Beginning of Line`
  This setting binds <Ctrl+A> to the ‘`Beginning of Line`’ operation, as used in several UNIX text-editing programs. In this setting, use <Ctrl+Shift+A> to select all text.

Here are the related DDD resources:

— Resource: cutCopyPasteBindings (class BindingStyle)

> Controls the key bindings for clipboard operations.

> - If this is ‘`Motif`’ (default), Cut/Copy/Paste is on <Shift+Del>/<Ctrl+Ins>/<Shift+Ins>. This is conformant to the M*tif style guide.
> - If this is ‘`KDE`’, Cut/Copy/Paste is on <Ctrl+X>/<Ctrl+C>/<Ctrl+V>. This is conformant to the KDE style guide. Note that this means that <Ctrl+C> no longer interrupts the debuggee; use <ESC> instead.

— Resource: selectAllBindings (class BindingStyle)

> Controls the key bindings for the ‘`Select All`’ operation.

> - If this is ‘`Motif`’, Select All is on <Shift+Ctrl+A>.
> - If this is ‘`KDE`’ (default), Select All is on <Ctrl+A>. This is conformant to the KDE style guide. Note that this means that <Ctrl+A> no longer moves the cursor to the beginning of a line; use <Home> instead.

Next: Command Tool, Previous: Menu Bar, Up: Windows

### 3.2 The Tool Bar

Some DDD commands require an argument. This argument is specified in the argument field, labeled ‘`():`’. Basically, there are four ways to set arguments:

- You can key in the argument manually.
- You can paste the current selection into the argument field (typically using `mouse button 2`). To clear old contents beforehand, click on the ‘`():`’ label.
- You can select an item from the source and data windows. This will automatically copy the item to the argument field.
- You can select a previously used argument from the drop-down menu at the right of the argument field.

Using GDB and Perl, the argument field provides a completion mechanism. You can enter the first few characters of an item an press the <TAB> key to complete it. Pressing <TAB> again shows alternative completions.

After having entered an argument, you can select one of the buttons on the right. Most of these buttons also have menus associated with them; this is indicated by a small arrow in the upper right corner. Pressing and holding mouse button 1 on such a button will pop up a menu with further operations.

These are the buttons of the tool bar. Note that not all buttons may be inactive, depending on the current state and the capabilities of the inferior debugger.

`Lookup`
  Look up the argument ‘`()`’ in the source code. See Looking up Definitions, for details.
`Find >>`
  Look up the next occurrence of the argument ‘`()`’ in the current source code. See Textual Search, for details.
`Break/Clear`
  Toggle a breakpoint (see Breakpoints) at the location ‘`()`’.
  `Break`
    If there is no breakpoint at ‘`()`’, then this button is labeled ‘`Break`’. Clicking on ‘`Break`’ sets a breakpoint at the location ‘`()`’. See Setting Breakpoints, for details.
  `Clear`
    If there already is a breakpoint at ‘`()`’, then this button is labeled ‘`Clear`’. Clicking on ‘`Clear`’ clears (deletes) the breakpoint at the location ‘`()`’. See Deleting Breakpoints, for details.
`Watch/Unwatch`
  Toggle a watchpoint (see Watchpoints) on the expression ‘`()`’.
  `Watch`
    If ‘`()`’ is not being watched, then this button is labeled ‘`Watch`’. Clicking on ‘`Watch`’ creates a watchpoint on the expression ‘`()`’. See Setting Watchpoints, for details.
  `Unwatch`
    If ‘`()`’ is being watched, then this button is labeled ‘`Unwatch`’. Clicking on ‘`Unwatch`’ clears (deletes) the watchpoint on ‘`()`’. See Deleting Watchpoints, for details.
`Print`
  Print the value of ‘`()`’ in the debugger console. See Printing Values, for details.
`Display`
  Display the value of ‘`()`’ in the data window. See Displaying Values, for details.
`Plot`
  Plot ‘`()`’ in a plot window. See Plotting Values, for details.
`Show/Hide`
  Toggle details of the selected display(s). See Showing and Hiding Details, for a discussion.
`Rotate`
  Rotate the selected display(s). See Rotating Displays, for details.
`Set`
  Set (change) the value of ‘`()`’. See Assignment, for details.
`Undisp`
  Undisplay (delete) the selected display(s). See Deleting Displays, for details.

Up: Tool Bar

#### 3.2.1 Customizing the Tool Bar

The DDD tool bar buttons can appear in a variety of styles, customized via ‘`Edit Preferences Startup`’.

`Images`
  This lets each tool bar button show an image illustrating the action.
`Captions`
  This shows the action name below the image.

The default is to have images as well as captions, but you can choose to have only images (saving space) or only captions.

If you choose to have neither images nor captions, tool bar buttons are labeled like other buttons, as in DDD 2.x. Note that this implies that in the stacked window configuration, the common tool bar cannot be displayed; it is replaced by two separate tool bars, as in DDD 2.x.

If you enable ‘`Flat`’ buttons (default), the border of tool bar buttons will appear only if the mouse pointer is over them. This latest-and-greatest GUI invention can be disabled, such that the button border is always shown.

If you enable ‘`Color`’ buttons, tool bar images will be colored when entered. If DDD was built using M*tif 2.0 and later, you can also choose a third setting, where buttons appear in color all the time.

Here are the related resources (see Customizing):

— Resource: activeButtonColorKey (class ColorKey)

> The XPM color key to use for the images of active buttons (entered or armed). ‘`c`’ means color, ‘`g`’ (default) means grey, and ‘`m`’ means monochrome.

— Resource: buttonCaptions (class ButtonCaptions)

> Whether the tool bar buttons should be shown using captions (‘`on`’, default) or not (‘`off`’). If neither captions nor images are enabled, tool bar buttons are shown using ordinary labels. See also ‘`buttonImages`’, below.

— Resource: buttonCaptionGeometry (class ButtonCaptionGeometry)

> The geometry of the caption subimage within the button icons. Default is ‘`29x7+0-0`’.

— Resource: buttonImages (class ButtonImages)

> Whether the tool bar buttons should be shown using images (‘`on`’, default) or not (‘`off`’). If neither captions nor images are enabled, tool bar buttons are shown using ordinary labels. See also ‘`buttonCaptions`’, above.

— Resource: buttonImageGeometry (class ButtonImageGeometry)

> The geometry of the image within the button icon. Default is ‘`25x21+2+0`’.

— Resource: buttonColorKey (class ColorKey)

> The XPM color key to use for the images of inactive buttons (non-entered or insensitive). ‘`c`’ means color, ‘`g`’ (default) means grey, and ‘`m`’ means monochrome.

— Resource: flatToolbarButtons (class FlatButtons)

> If ‘`on`’ (default), all tool bar buttons with images or captions are given a `flat' appearance—the 3-D border only shows up when the pointer is over the icon. If ‘`off`’, the 3-D border is shown all the time.

— Resource: flatDialogButtons (class FlatButtons)

> If ‘`on`’ (default), all dialog buttons with images or captions are given a `flat' appearance—the 3-D border only shows up when the pointer is over the icon. If ‘`off`’, the 3-D border is shown all the time.

Next: Getting Help, Previous: Tool Bar, Up: Windows

### 3.3 The Command Tool

The command tool is a small window that gives you access to the most frequently used DDD commands. It can be moved around on top of the DDD windows, but it can also be placed besides them.

By default, the command tool sticks to the DDD source window: Whenever you move the DDD source window, the command tool follows such that the distance between source window and command tool remains the same. By default, the command tool is also auto-raised, such that it stays on top of other DDD windows.

The command tool can be configured to appear as a command tool bar above the source window; see ‘`Edit Preferences Source Tool Buttons Location`’ for details.

Whenever you save DDD state, DDD also saves the distance between command tool and source window, such that you can select your own individual command tool placement. To move the command tool to its saved position, use ‘`View Command Tool`’.

These are the buttons of the command tool. Note that not all buttons may be inactive, depending on the current state and the capabilities of the inferior debugger.

`Run`
  Start program execution. When you click this button, your program will begin to execute immediately. See Starting Program Execution, for details.
`Interrupt`
  Interrupt program execution. This is equivalent to sending an interrupt signal to the process. See Interrupting, for details.
`Step`
  Continue running your program until control reaches a different source line, then stop it and return control to DDD. See Resuming Execution, for details.
`Stepi`
  Execute one machine instruction, then stop and return to DDD. See Machine Code Execution, for details.
`Next`
  Continue to the next source line in the current (innermost) stack frame. This is similar to ‘`Step`’, but function calls that appear within the line of code are executed without stopping. See Resuming Execution, for details.
`Nexti`
  Execute one machine instruction, but if it is a function call, proceed until the function returns. See Machine Code Execution, for details.
`Until`
  Continue running until a source line past the current line, in the current stack frame, is reached. See Resuming Execution, for details.
`Finish`
  Continue running until just after function in the selected stack frame returns. Print the returned value (if any). See Resuming Execution, for details.
`Cont`
  Resume program execution, at the address where your program last stopped; any breakpoints set at that address are bypassed. See Resuming Execution, for details.
`Kill`
  Kill the process of the debugged program. See Killing the Program, for details.
`Up`
  Select the stack frame (i.e. the function) that called this one. This advances toward the outermost frame, to higher frame numbers, to frames that have existed longer. See Stack, for details.
`Down`
  Select the stack frame (i.e. the function) that was called by this one. This advances toward the innermost frame, to lower frame numbers, to frames that were created more recently. See Stack, for details.
`Undo`
  Undo the most recent action. Almost all commands can be undone this way. See Undo and Redo, for details.
`Redo`
  Redo the action most recently undone. Every command undone can be redone this way. See Undo and Redo, for details.
`Edit`
  Invoke an editor for the current source file. See Editing Source Code, for details.
`Make`
  Run the `make` program with the most recently given arguments. See Recompiling, for details.

Next: Customizing Tool Position, Up: Command Tool

#### 3.3.1 Customizing the Command Tool

The Command Tool can be customized in various ways.

See Customizing Buttons, for details on customizing the tool buttons.

Up: Customizing the Command Tool

##### 3.3.1.1 Disabling the Command Tool

You can disable the command tool and show its buttons in a separate row beneath the tool bar. To disable the command tool, set ‘`Edit Preferences Source Tool Buttons Location Source Window`’.

Here's the related resource:
— Resource: commandToolBar (class ToolBar)

> Whether the tool buttons should be shown in a tool bar above the source window (‘`on`’) or within the command tool (‘`off`’, default). Enabling the command tool bar disables the command tool and vice versa.

Previous: Customizing the Command Tool, Up: Command Tool

#### 3.3.2 Command Tool Position

The following resources control the position of the command tool (see Customizing):

— Resource: autoRaiseTool (class AutoRaiseTool)

> If ‘`on`’ (default), DDD will always keep the command tool on top of other DDD windows. If this setting interferes with your window manager, or if your window manager keeps the command tool on top anyway, set this resource to ‘`off`’.

— Resource: stickyTool (class StickyTool)

> If ‘`on`’ (default), the command tool automatically follows every movement of the source window. Whenever the source window is moved, the command tool is moved by the same offset such that its position relative to the source window remains unchanged. If ‘`off`’, the command tool does not follow source window movements.

— Resource: toolRightOffset (class Offset)

> The distance between the right border of the command tool and the right border of the source text (in pixels). Default is 8.

— Resource: toolTopOffset (class Offset)

> The distance between the upper border of the command tool and the upper border of the source text (in pixels). Default is 8.

Up: Customizing Tool Position

##### 3.3.2.1 Customizing Tool Decoration

The following resources control the decoration of the command tool (see Customizing):

— Resource: decorateTool (class Decorate)

> This resource controls the decoration of the command tool.

> - If this is ‘`off`’, the command tool is created as a transient window. Several window managers keep transient windows automatically on top of their parents, which is appropriate for the command tool. However, your window manager may be configured not to decorate transient windows, which means that you cannot easily move the command tool around.
> - If this is ‘`on`’, DDD realizes the command tool as a top-level window. Such windows are always decorated by the window manager. However, top-level windows are not automatically kept on top of other windows, such that you may wish to set the ‘`autoRaiseTool`’ resource, too.
> - If this is ‘`auto`’ (default), DDD checks whether the window manager decorates transients. If yes, the command tool is realized as a transient window (as in the ‘`off`’ setting); if no, the command tool is realized as a top-level window (as in the ‘`on`’ setting). Hence, the command tool is always decorated using the “best” method, but the extra check takes some time.

Next: Undo and Redo, Previous: Command Tool, Up: Windows

### 3.4 Getting Help

DDD has an extensive on-line help system. Here's how to get help while working with DDD.

- You can get a short help text on most DDD buttons by simply moving the mouse pointer on it and leave it there. After a second, a small window (called button tip; also known as tool tip or balloon help) pops up, giving a hint on the button's meaning. The button tip disappears as soon as you move the mouse pointer to another item.
- The status line also displays information about the currently selected item. By clicking on the status line, you can redisplay the most recent messages.
- You can get detailed help on any visible DDD item. Just point on the item you want help and press the ‘`F1`’ key. This pops up a detailed help text.
- The DDD dialogs all contain ‘`Help`’ buttons that give detailed information about the dialog.
- You can get help on debugger commands by entering `help` at the debugger prompt. See Entering Commands, for details on entering commands.
- If you are totally stuck, try ‘`Help What Now?`’ (the ‘`What Now?`’ item in the ‘`Help`’ menu) or press <Ctrl+F1>. Depending on the current state, DDD will give you some hints on what you can do next.
- Of course, you can always refer to the on-line documentation:
  - ‘`Help DDD Reference`’ gives you access to the DDD manual, the ultimate DDD reference.
  - ‘`Help Debugger Reference`’ shows you the on-line documentation of the inferior debugger.
  - ‘`Help DDD WWW Page`’ gives you access to the latest and greatest information on DDD.
- Finally, the DDD Tip Of The Day gives you important hints with each new DDD invocation.

All these functions can be customized in various ways (see Customizing Help).

If, after all, you made a mistake, don't worry: almost every DDD command can be undone. See Undo and Redo, for details.

Next: Customizing, Previous: Getting Help, Up: Windows

### 3.5 Undoing and Redoing Commands

Almost every DDD command can be undone, using ‘`Edit Undo`’ or the ‘`Undo`’ button on the command tool.

Likewise, ‘`Edit Redo`’ repeats the command most recently undone.

The ‘`Edit`’ menu shows which commands are to be undone and redone next; this is also indicated by the popup help on the ‘`Undo`’ and ‘`Redo`’ buttons.

Previous: Undo and Redo, Up: Windows

### 3.6 Customizing DDD

DDD is controlled by several resources—user-defined variables that take specific values in order to control and customize DDD behavior.

Most DDD resources can be set interactively while DDD is running or when invoking DDD. See Resource Index, for the full list of DDD resources.

We first discuss how customizing works in general; then we turn to customizing parts of DDD introduced so far.

Next: Customizing Help, Up: Customizing

#### 3.6.1 How Customizing DDD Works

Next: Changing Resources, Up: How Customizing Works

##### 3.6.1.1 Resources

Just like any X program, DDD has a number of places to get resource values from. For DDD, the most important places to specify resources are:

- The `~/.ddd/init` file (`~` stands for your home directory). This file is read in by DDD upon start-up; the resources specified herein override all other sources (except for resources given implicitly by command-line options).

  If the environment variable `DDD_STATE` is set, its value is used instead of `~/.ddd/`.

- The `Ddd` application-defaults file. This file is typically compiled into the DDD executable. If it exists, its resource values override the values compiled into DDD. If the versions of the `Ddd` application-defaults file and the DDD executable do not match, DDD may not function properly; DDD will give you a warning in this case.8
- The command-line options. These options override all other resource settings.
- If the environment variable `DDD_SESSION` is set, it indicates the name of a session to start, overriding all options and resources. This is used by DDD when restarting itself.

Not every resource has a matching command-line option. Each resource (whether in `~/.ddd/init` or `Ddd`) is specified using a line

         Ddd*resource: value

For instance, to set the ‘`pollChildStatus`’ resource to ‘`off`’, you would specify in `~/.ddd/init`:

         Ddd*pollChildStatus: off

For more details on the syntax of resource specifications, see the section RESOURCES in the X(1) manual page.

Next: Saving Options, Previous: Resources, Up: How Customizing Works

##### 3.6.1.2 Changing Resources

You can change DDD resources by three methods:

- Use DDD to change the options, notably ‘`Edit Preferences`’. This works for the most important DDD resources. Be sure to save the options (see Saving Options) such that they apply to future DDD sessions, too.
- You can also invoke DDD with an appropriate command-line option. This changes the related DDD resource for this particular DDD invocation. However, if you save the options (see Saving Options), the changed resource will also apply to future invocations.
- Finally, you can set the appropriate resource in a file named `.ddd/init` in your home directory. See Resource Index, for a list of DDD resources to be set.

Previous: Changing Resources, Up: How Customizing Works

##### 3.6.1.3 Saving Options

You can save the current option settings by setting ‘`Edit Save Options`’. Options are saved in a file named `.ddd/init` in your home directory when DDD exits. If a session session is active, options will be saved in `~/.ddd/sessions/session/init` instead.

The options are automatically saved when exiting DDD. You can turn off this feature by unsetting ‘`Edit Save Options`’. This is tied to the following resource:

— Resource: saveOptionsOnExit (class SaveOnExit)

> If ‘`on`’ (default), the current option settings are automatically saved when DDD exits.

Next: Customizing Undo, Previous: How Customizing Works, Up: Customizing

#### 3.6.2 Customizing DDD Help

DDD Help can be customized in various ways.

Next: Tip of the day, Up: Customizing Help

##### 3.6.2.1 Button Tips

Button tips are helpful for novices, but may be distracting for experienced users. You can turn off button tips via ‘`Edit Preferences General Automatic display of Button Hints as Popup Tips`’.

You can also turn off the hint that is displayed in the status line. Just toggle ‘`Edit Preferences General Automatic Display of Button Hints in the Status Line`’.

These are the related DDD resources (see Customizing):
— Resource: buttonTips (class Tips)

> If ‘`on`’ (default), enable button tips.

— Resource: buttonDocs (class Docs)

> If ‘`on`’ (default), show button hints in the status line.

Next: Help Helpers, Previous: Button tips, Up: Customizing Help

##### 3.6.2.2 Tip of the day

You can turn off the tip of the day by toggling ‘`Edit Preferences Startup Startup Windows Tip of the Day`’.

Here is the related DDD resource (see Customizing):

— Resource: startupTips (class StartupTips)

> If ‘`on`’ (default), show a tip of the day upon DDD startup.

See Options, for options to set this resource upon DDD invocation.

The actual tips are controlled by these resources (see Customizing):

— Resource: startupTipCount (class StartupTipCount)

> The number n of the tip of the day to be shown at startup. See also the ‘`tipn`’ resources.

— Resource: tipn (class Tip)

> The tip of the day numbered n (a string).

Previous: Tip of the day, Up: Customizing Help

##### 3.6.2.3 Help Helpers

DDD relies on a number of external commands, specified via ‘`Edit Preferences Helpers`’.

To uncompress help texts, you can define a ‘`Uncompress`’ command:
— Resource: uncompressCommand (class UncompressCommand)

> The command to uncompress the built-in DDD manual, the DDD license, and the DDD news. Takes a compressed text from standard input and writes the uncompressed text to standard output. The default value is `gzip -d -c`; typical values include `zcat` and `gunzip -c`.

To view WWW pages, you can define a ‘`Web Browser`’ command:

— Resource: wwwCommand (class WWWCommand)

> The command to invoke a WWW browser. The string ‘`@URL@`’ is replaced by the URL to open. Default is to try a running Netscape first (trying `mozilla`, then `netscape`), then `$WWWBROWSER`, then to invoke a new Netscape process, then to let a running Emacs or XEmacs do the job (via `gnudoit`), then to invoke Firefox, then to invoke Lynx in an xterm.

> To specify ‘`netscape-6.0`’ as browser, use the setting:

>               Ddd*wwwCommand: \
>                    netscape-6.0 -remote 'openURL(@URL@)' \
>                 || netscape-6.0 '@URL@'

> This command first tries to connect to a running `netscape-6.0` browser; if this fails, it starts a new `netscape-6.0` process.

This is the default WWW Page shown by ‘`Help DDD WWW Page`’:

— Resource: wwwPage (class WWWPage)

> The DDD WWW page. Value: http://www.gnu.org/software/ddd/

Next: Customizing Windows, Previous: Customizing Help, Up: Customizing

#### 3.6.3 Customizing Undo

DDD Undo can be customized in various ways.

To set a maximum size for the undo buffer, set ‘`Edit Preferences General Undo Buffer Size`’.

This is related to the ‘`maxUndoSize`’ resource:

— Resource: maxUndoSize (class MaxUndoSize)

> The maximum memory usage (in bytes) of the undo buffer. Useful for limiting DDD memory usage. A negative value means to place no limit. Default is `2000000`, or 2000 kBytes.

You can also limit the number of entries in the undo buffer, regardless of size (see Customizing):

— Resource: maxUndoDepth (class MaxUndoDepth)

> The maximum number of entries in the undo buffer. This limits the number of actions that can be undone, and the number of states that can be shown in historic mode. Useful for limiting DDD memory usage. A negative value (default) means to place no limit.

To clear the undo buffer at any time, thus reducing memory usage, use ‘`Edit Preferences General Clear Undo Buffer`’

Next: Debugger Settings, Previous: Customizing Undo, Up: Customizing

#### 3.6.4 Customizing the DDD Windows

You can customize the DDD Windows in various ways.

Next: Window Layout, Up: Customizing Windows

##### 3.6.4.1 Splash Screen

You can turn off the DDD splash screen shown upon startup. Just select ‘`Edit Preferences Startup DDD Splash Screen`’.

The value applies only to the next DDD invocation.

This setting is related to the following resource:

— Resource: splashScreen (class SplashScreen)

> If ‘`on`’ (default), show a DDD splash screen upon start-up.

You can also customize the appearance of the splash screen (see Customizing):

— Resource: splashScreenColorKey (class ColorKey)

> The color key to use for the DDD splash screen. Possible values include:

> - ‘`c`’ (default) for a color visual,
> - ‘`g`’ for a multi-level greyscale visual,
> - ‘`g4`’ for a 4-level greyscale visual, and
> - ‘`m`’ for a dithered monochrome visual.
> - ‘`best`’ chooses the best visual available for your display.

> Please note: if DDD runs on a monochrome display, or if DDD was compiled without the XPM library, only the monochrome version (‘`m`’) can be shown.

Next: Customizing Fonts, Previous: Splash Screen, Up: Customizing Windows

##### 3.6.4.2 Window Layout

By default, DDD stacks commands, source, and data in one single top-level window. To have separate top-level windows for source, data, and debugger console, set ‘`Edit Preferences Startup Window Layout Separate Windows`’.

Here are the related DDD resources:
— Resource: separateDataWindow (class Separate)

> If ‘`on`’, the data window and the debugger console are realized in different top-level windows. If ‘`off`’ (default), the data window is attached to the debugger console.

— Resource: separateSourceWindow (class Separate)

> If ‘`on`’, the source window and the debugger console are realized in different top-level windows. If ‘`off`’ (default), the source window is attached to the debugger console.

By default, the DDD tool bars are located on top of the window. If you prefer the tool bar being located at the bottom, as in DDD 2.x and earlier, set ‘`Edit Preferences Startup Tool Bar Appearance Bottom`’.

This is related to the ‘`toolbarsAtBottom`’ resource:

— Resource: toolbarsAtBottom (class ToolbarsAtBottom)

> Whether source and data tool bars should be placed above source and data, respectively (‘`off`’, default), or below, as in DDD 2.x (‘`on`’).

The bottom setting is only supported for separate tool bars—that is, you must either choose separate windows or configure the tool bar to have neither images nor captions (see Customizing the Tool Bar).

If you use stacked windows, you can choose whether there should be one tool bar or two tool bars. By default, DDD uses two tool bars if you use separate windows and disable captions and images, but you can also explicitly change the setting via this resource:

— Resource: commonToolBar (class ToolBar)

> Whether the tool bar buttons should be shown in one common tool bar at the top of the common DDD window (‘`on`’, default), or whether they should be placed in two separate tool bars, one for data, and one for source operations, as in DDD 2.x (‘`off`’).

You can also change the location of the status line (see Customizing):

— Resource: statusAtBottom (class StatusAtBottom)

> If ‘`on`’ (default), the status line is placed at the bottom of the DDD source window. If ‘`off`’, the status line is placed at the top of the DDD source window (as in DDD 1.x).

See Options, for options to set these resources upon DDD invocation.

Next: Toggling Windows, Previous: Window Layout, Up: Customizing Windows

##### 3.6.4.3 Customizing Fonts

You can configure the basic DDD fonts at run-time. Each font is specified using two members:

- The font family is an X font specifications, where the initial ‘`foundry-`’ specification may be omitted, as well as any specification after family. Thus, a pair ‘`family-weight`’ usually suffices.
- The font size is given as (resolution-independent) 1/10 points.

To specify fonts, select ‘`Edit Preferences Fonts`’.

The ‘`Browse`’ button opens a font selection program, where you can select fonts and attributes interactively. Clicking ‘`quit`’ or ‘`select`’ in the font selector causes all non-default values to be transferred to the DDD font preferences panel.

The following fonts can be set using the preferences panel:

`Default Font`
  The default DDD font to use for labels, menus, and buttons. Default is ‘`helvetica-bold`’.
`Variable Width`
  The variable width DDD font to use for help texts and messages. Default is ‘`helvetica-medium`’.
`Fixed Width`
  The fixed width DDD font to use for source code, the debugger console, text fields, and the execution window. Default is ‘`lucidatypewriter-medium`’.
`Data`
  The DDD font to use for data displays. Default is ‘`lucidatypewriter-medium`’.

Changes in this panel will take effect only in the next DDD session. To make it effective right now, restart DDD (using ‘`File Restart DDD`’).

After having made changes in the panel, DDD will automatically offer you to restart itself, such that you can see the changes taking effect.

The ‘`Reset`’ button restores the most recently saved preferences.

Here are the resources related to font specifications:

— Resource: defaultFont (class Font)

> The default DDD font to use for labels, menus, buttons, etc. The font is specified as an X font spec, where the initial Foundry specification may be omitted, as well as any specification after Family.

> Default value is ‘`helvetica-bold`’.

> To set the default DDD font to, say, ‘`helvetica medium`’, insert a line

>               Ddd*defaultFont: helvetica-medium

> in your `~/.ddd/init` file.

— Resource: defaultFontSize (class FontSize)

> The size of the default DDD font, in 1/10 points. This resource overrides any font size specification in the ‘`defaultFont`’ resource (see above). The default value is `120` for a 12.0 point font.

— Resource: variableWidthFont (class Font)

> The variable width DDD font to use for help texts and messages. The font is specified as an X font spec, where the initial Foundry specification may be omitted, as well as any specification after Family.

> Default value is ‘`helvetica-medium-r`’.

> To set the variable width DDD font family to, say, ‘`times`’, insert a line

>               Ddd*fixedWidthFont: times-medium

> in your `~/.ddd/init` file.

— Resource: variableWidthFontSize (class FontSize)

> The size of the variable width DDD font, in 1/10 points. This resource overrides any font size specification in the ‘`variableWidthFont`’ resource (see above). The default value is `120` for a 12.0 point font.

— Resource: fixedWidthFont (class Font)

> The fixed width DDD font to use for source code, the debugger console, text fields, and the execution window. The font is specified as an X font spec, where the initial Foundry specification may be omitted, as well as any specification after Family.

> Default value is ‘`lucidatypewriter-medium`’.

> To set the fixed width DDD font family to, say, ‘`courier`’, insert a line

>               Ddd*fixedWidthFont: courier-medium

> in your `~/.ddd/init` file.

— Resource: fixedWidthFontSize (class FontSize)

> The size of the fixed width DDD font, in 1/10 points. This resource overrides any font size specification in the ‘`fixedWidthFont`’ resource (see above). The default value is `120` for a 12.0 point font.

— Resource: dataFont (class Font)

> The fixed width DDD font to use data displays. The font is specified as an X font spec, where the initial Foundry specification may be omitted, as well as any specification after Family.

> Default value is ‘`lucidatypewriter-medium`’.

> To set the DDD data font family to, say, ‘`courier`’, insert a line

>               Ddd*dataFont: courier-medium

> in your `~/.ddd/init` file.

— Resource: dataFontSize (class FontSize)

> The size of the DDD data font, in 1/10 points. This resource overrides any font size specification in the ‘`dataFont`’ resource (see above). The default value is `120` for a 12.0 point font.

As all font size resources have the same class (and by default the same value), you can easily change the default DDD font size to, say, 9.0 points by inserting a line

         Ddd*FontSize: 90

in your `~/.ddd/init` file.

Here's how to specify the command to select fonts:

— Resource: fontSelectCommand (class FontSelectCommand)

> A command to select from a list of fonts. The string ‘`@FONT@`’ is replaced by the current DDD default font; the string ‘`@TYPE@`’ is replaced by a symbolic name of the DDD font to edit. The program must either place the name of the selected font in the `PRIMARY` selection or print the selected font on standard output. A typical value is:

>               Ddd*fontSelectCommand: xfontsel -print

See Options, for options to set these resources upon DDD invocation.

Next: Text Fields, Previous: Customizing Fonts, Up: Customizing Windows

##### 3.6.4.4 Toggling Windows

In the default stacked window setting, you can turn the individual DDD windows on and off by toggling the respective items in the ‘`View`’ menu (see View Menu). When using separate windows (see Window Layout), you can close the individual windows via ‘`File Close`’ or by closing them via your window manager.

Whether windows are opened or closed when starting DDD is controlled by the following resources, immediately tied to the ‘`View`’ menu items:

— Resource: openDataWindow (class Window)

> If ‘`off`’ (default), the data window is closed upon start-up.

— Resource: openDebuggerConsole (class Window)

> If ‘`off`’, the debugger console is closed upon start-up.

— Resource: openSourceWindow (class Window)

> If ‘`off`’, the source window is closed upon start-up.

See Options, for options to set these resources upon DDD invocation.

Next: Icons, Previous: Toggling Windows, Up: Customizing Windows

##### 3.6.4.5 Text Fields

The DDD text fields can be customized using the following resources:

— Resource: popdownHistorySize (class HistorySize)

> The maximum number of items to display in pop-down value histories. A value of `0` (default) means an unlimited number of values.

— Resource: sortPopdownHistory (class SortPopdownHistory)

> If ‘`on`’ (default), items in the pop-down value histories are sorted alphabetically. If ‘`off`’, most recently used values will appear at the top.

Next: Adding Buttons, Previous: Text Fields, Up: Customizing Windows

##### 3.6.4.6 Icons

If you frequently switch between DDD and other multi-window applications, you may like to set ‘`Edit Preferences General Iconify all windows at once`’. This way, all DDD windows are iconified and deiconified as a group.

This is tied to the following resource:

— Resource: groupIconify (class GroupIconify)

> If this is ‘`on`’, (un)iconifying any DDD window causes all other DDD windows to (un)iconify as well. Default is ‘`off`’, meaning that each DDD window can be iconified on its own.

If you want to keep DDD off your desktop during a longer computation, you may like to set ‘`Edit Preferences General Uniconify when ready`’. This way, you can iconify DDD while it is busy on a command (e.g. running a program); DDD will automatically pop up again after becoming ready (e.g. after the debugged program has stopped at a breakpoint). See Program Stop, for a discussion.

Here is the related resource:

— Resource: uniconifyWhenReady (class UniconifyWhenReady)

> If this is ‘`on`’ (default), the DDD windows are uniconified automatically whenever GDB becomes ready. This way, you can iconify DDD during some longer operation and have it uniconify itself as soon as the program stops. Setting this to ‘`off`’ leaves the DDD windows iconified.

Next: More Customizations, Previous: Icons, Up: Customizing Windows

##### 3.6.4.7 Adding Buttons

You can extend DDD with new buttons. See Defining Buttons, for details.

Previous: Adding Buttons, Up: Customizing Windows

##### 3.6.4.8 More Customizations

You can change just about any label, color, keyboard mapping, etc. by changing resources from the `Ddd` application defaults file which comes with the DDD source distribution. Here's how it works:

- Identify the appropriate resource in the `Ddd` file.
- Copy the resource line to your `~/.ddd/init` file and change it at will.

See Application Defaults, for details on the application-defaults file.

Previous: Customizing Windows, Up: Customizing

#### 3.6.5 Debugger Settings

For most inferior debuggers, you can change their internal settings using ‘`Edit Settings`’. Using the settings editor, you can determine whether C++ names are to be demangled, how many array elements are to print, and so on.

The capabilities of the settings editor depend on the capabilities of your inferior debugger. Clicking on ‘`?`’ gives an an explanation on the specific item; the GDB documentation gives more details.

Use ‘`Edit Undo`’ to undo changes. Clicking on ‘`Reset`’ restores the most recently saved settings.

Some debugger settings are insensitive and cannot be changed, because doing so would endanger DDD operation. See the ‘`gdbInitCommands`’ and ‘`dbxInitCommands`’ resources for details.

All debugger settings (except source and object paths) are saved with DDD options.

Next: Stopping, Previous: Windows, Up: Top

## 4 Navigating through the Code

This chapter discusses how to access code from within DDD.

Next: Opening Files, Up: Navigating

### 4.1 Compiling for Debugging

In order to debug a program effectively, you need to generate debugging information when you compile it. This debugging information is stored in the object file; it describes the data type of each variable or function and the correspondence between source line numbers and addresses in the executable code.9

To request debugging information, specify the `-g` option when you run the compiler.

Many C compilers are unable to handle the `-g` and `-O` options together. Using those compilers, you cannot generate optimized executables containing debugging information.

GCC, the GNU C compiler, supports `-g` with or without `-O`, making it possible to debug optimized code. We recommend that you always use `-g` whenever you compile a program. You may think your program is correct, but there is no sense in pushing your luck.

When you debug a program compiled with `-g -O`, remember that the optimizer is rearranging your code; the debugger shows you what is really there. Do not be too surprised when the execution path does not exactly match your source file! An extreme example: if you define a variable, but never use it, DDD never sees that variable—because the compiler optimizes it out of existence.

Next: Looking up Items, Previous: Compiling for Debugging, Up: Navigating

### 4.2 Opening Files

If you did not invoke DDD specifying a program to be debugged, you can use the ‘`File`’ menu to open programs, core dumps and sources.

Next: Opening Core Dumps, Up: Opening Files

#### 4.2.1 Opening Programs

To open a program to be debugged, select ‘`File Open Program`’.10 Click on ‘`Open`’ to open the program

In JDB, select ‘`File Open Class`’ instead. This gives you a list of available classes to choose from.

To re-open a recently debugged program or class, select ‘`File Open Recent`’ and choose a program or class from the list.

If no sources are found, See Source Path, for specifying source directories.

Next: Opening Source Files, Previous: Opening Programs, Up: Opening Files

#### 4.2.2 Opening Core Dumps

If a previous run of the program has crashed and you want to find out why, you can have DDD examine its core dump.11

To open a core dump for the program, select ‘`File Open Core Dump`’. Click on ‘`Open`’ to open the core dump.

Before ‘`Open Core Dump`’, you should first use ‘`File Open Program`’ to specify the program that generated the core dump and to load its symbol table.

Next: Filtering Files, Previous: Opening Core Dumps, Up: Opening Files

#### 4.2.3 Opening Source Files

To open a source file of the debugged program, select ‘`File Open Source`’.

- Using GDB, this gives you a list of the sources used for compiling your program.
- Using other inferior debuggers, this gives you a list of accessible source files, which may or may not be related to your program.

Click on ‘`Open`’ to open the source file. See Source Path, if no sources are found.

Previous: Opening Source Files, Up: Opening Files

#### 4.2.4 Filtering Files

When presenting files to be opened, DDD by default filters files when opening execution files, core dumps, or source files, such that the selection shows only suitable files. This requires that DDD opens each file, which may take time. See Customizing File Filtering, if you want to turn off this feature.

Next: Customizing Source, Previous: Opening Files, Up: Navigating

### 4.3 Looking up Items

As soon as the source of the debugged program is available, the source window displays its current source text. (see Source Path, if a source text cannot be found.)

In the source window, you can lookup and examine function and variable definitions as well as search for arbitrary occurrences in the source text.

Next: Textual Search, Up: Looking up Items

#### 4.3.1 Looking up Definitions

If you wish to lookup a specific function or variable definition whose name is visible in the source text, click with mouse button 1 on the function or variable name. The name is copied to the argument field. Change the name if desired and click on the ‘`Lookup`’ button to find its definition.

As a faster alternative, you can simply press mouse button 3 on the function name and select the ‘`Lookup`’ item from the source popup menu.

As an even faster alternative, you can also double-click on a function call (an identifier followed by a ‘`(`’ character) to lookup the function definition.

If a source file is not found, See Source Path, for specifying source directories.

Next: Looking up Previous Locations, Previous: Looking up Definitions, Up: Looking up Items

#### 4.3.2 Textual Search

If the item you wish to search is visible in the source text, click with mouse button 1 on it. The identifier is copied to the argument field. Click on the ‘`Find >>`’ button to find following occurrences and on ‘`Find >> Find << ()`’ to find previous occurrences.

By default, DDD finds only complete words. To search for arbitrary substrings, change the value of the ‘`Source Find Words Only`’ option.

Next: Source Path, Previous: Textual Search, Up: Looking up Items

#### 4.3.3 Looking up Previous Locations

After looking up a location, use ‘`Edit Undo`’ (or the ‘`Undo`’ button on the command tool) to go back to the original locations. ‘`Edit Redo`’ brings you back again to the location you looked for.

Previous: Looking up Previous Locations, Up: Looking up Items

#### 4.3.4 Specifying Source Directories

Executable programs sometimes do not record the directories of the source files from which they were compiled, just the names. Even when they do, the directories could be moved between the compilation and your debugging session.

Here's how GDB accesses source files; other inferior debuggers have similar methods.

GDB has a list of directories to search for source files; this is called the source path. Each time GDB wants a source file, it tries all the directories in the list, in the order they are present in the list, until it finds a file with the desired name. Note that the executable search path is not used for this purpose. Neither is the current working directory, unless it happens to be in the source path.

If GDB cannot find a source file in the source path, and the object program records a directory, GDB tries that directory too. If the source path is empty, and there is no record of the compilation directory, GDB looks in the current directory as a last resort.

To specify a source path for your inferior debugger, use ‘`Edit Debugger Settings`’ (see Debugger Settings and search for appropriate entries (in GDB, this is ‘`Search path for source files`’).

If ‘`Debugger Settings`’ has no suitable entry, you can also specify a source path for the inferior debugger when invoking DDD. See Inferior Debugger Options, for details.

When using JDB, you can set the `CLASSPATH` environment variable to specify directories where JDB (and DDD) should search for classes.

If DDD does not find a source file for any reason, check the following issues:

- In order to debug a program effectively, you need to generate debugging information when you compile it. Without debugging information, the inferior debugger will be unable to locate the source code. To request debugging information, specify the `-g` option when you run the compiler. See Compiling for Debugging, for details.
- You may need to tell your inferior debugger where the source code files are. See Source Path, for details.

  Using GDB, you can also create a local `.gdbinit` file that contains a line `directory path`. Here, path is a colon-separated list of source paths.

Previous: Looking up Items, Up: Navigating

### 4.4 Customizing the Source Window

The source window can be customized in a number of ways, most of them accessed via ‘`Edit Preferences Source`’.

Next: Customizing Searching, Up: Customizing Source

#### 4.4.1 Customizing Glyphs

In the source text, the current execution position and breakpoints are indicated by symbols (glyphs). As an alternative, DDD can also indicate these positions using text characters. If you wish to disable glyphs, set ‘`Edit Preferences Source Show Position and Breakpoints as Text Characters`’ option. This also makes DDD run slightly faster, especially when scrolling.

This setting is tied to this resource:

— Resource: displayGlyphs (class DisplayGlyphs)

> If this is ‘`on`’, the current execution position and breakpoints are displayed as glyphs; otherwise, they are shown through characters in the text. The default is ‘`on`’. See Options, for the `--glyphs` and `--no-glyphs` options.

You can further control glyphs using the following resources:

— Resource: cacheGlyphImages (class CacheMachineCode)

> Whether to cache (share) glyph images (‘`on`’) or not (‘`off`’). Caching glyph images requires less X resources, but has been reported to fail with OSF/Motif 2.1 on XFree86 servers. Default is ‘`off`’ for OSF/Motif 2.1 or later on GNU/Linux machines, and ‘`on`’ otherwise.

— Resource: glyphUpdateDelay (class GlyphUpdateDelay)

> A delay (in ms) that says how much time to wait before updating glyphs while scrolling the source text. A small value results in glyphs being scrolled with the text, a large value disables glyphs while scrolling and makes scrolling faster. Default: `10`.

— Resource: maxGlyphs (class MaxGlyphs)

> The maximum number of glyphs to be displayed (default: `10`). Raising this value causes more glyphs to be allocated, possibly wasting resources that are never needed.

Next: Customizing Source Appearance, Previous: Customizing Glyphs, Up: Customizing Source

#### 4.4.2 Customizing Searching

Searching in the source text (see Textual Search) is controlled by these resources, changed via the ‘`Source`’ menu:

— Resource: findCaseSensitive (class FindCaseSensitive)

> If this is ‘`on`’ (default), the ‘`Find`’ commands are case-sensitive. Otherwise, occurrences are found regardless of case.

— Resource: findWordsOnly (class FindWordsOnly)

> If this is ‘`on`’ (default), the ‘`Find`’ commands find complete words only. Otherwise, arbitrary occurrences are found.

Next: Customizing Source Scrolling, Previous: Customizing Searching, Up: Customizing Source

#### 4.4.3 Customizing Source Appearance

You can have DDD show line numbers within the source window. Use ‘`Edit Preferences Source Display Source Line Numbers`’.

— Resource: displayLineNumbers (class DisplayLineNumbers)

> If this is ‘`on`’, lines in the source text are prefixed with their respective line number. The default is ‘`off`’.

You can instruct DDD to indent the source code, leaving more room for breakpoints and execution glyphs. This is done using the ‘`Edit Preferences Source Source indentation`’ slider. The default value is `0` for no indentation at all.

— Resource: indentSource (class Indent)

> The number of columns to indent the source code, such that there is enough place to display breakpoint locations. Default: `0`.

By default, DDD uses a minimum indentation for script languages.

— Resource: indentScript (class Indent)

> The minimum indentation for script languages, such as Perl, Python, and Bash. Default: `4`.

The maximum width of line numbers is controlled by this resource.

— Resource: lineNumberWidth (class LineNumberWidth)

> The number of columns to use for line numbers (if displaying line numbers is enabled). Line numbers wider than this value extend into the breakpoint space. Default: `4`.

If your source code uses a tab width different from `8` (the default), you can set an alternate width using the ‘`Edit Preferences Source Tab width`’ slider.

— Resource: tabWidth (class TabWidth)

> The tab width used in the source window (default: `8`)

Next: Customizing Source Lookup, Previous: Customizing Source Appearance, Up: Customizing Source

#### 4.4.4 Customizing Source Scrolling

These resources control when the source window is scrolled:

— Resource: linesAboveCursor (class LinesAboveCursor)

> The minimum number of lines to show before the current location. Default is `2`.

— Resource: linesBelowCursor (class LinesBelowCursor)

> The minimum number of lines to show after the current location. Default is `3`.

Next: Customizing File Filtering, Previous: Customizing Source Scrolling, Up: Customizing Source

#### 4.4.5 Customizing Source Lookup

Some DBX and XDB variants do not properly handle paths in source file specifications. If you want the inferior debugger to refer to source locations by source base names only, unset the ‘`Edit Preferences Source Refer to Program Sources by full path name`’ option.

This is related to the following resource:

— Resource: useSourcePath (class UseSourcePath)

> If this is ‘`off`’ (default), the inferior debugger refers to source code locations only by their base names. If this is ‘`on`’ (default), DDD uses the full source code paths.

By default, DDD caches source files in memory. This is convenient for remote debugging, since remote file access may be slow. If you want to reduce memory usage, unset the ‘`Edit Preferences Source Cache source files`’ option.

This is related to the following resource:

— Resource: cacheSourceFiles (class CacheSourceFiles)

> Whether to cache source files (‘`on`’, default) or not (‘`off`’). Caching source files requires more memory, but makes DDD run faster.

Previous: Customizing Source Lookup, Up: Customizing Source

#### 4.4.6 Customizing File Filtering

You can control whether DDD should filter files to be opened.

— Resource: filterFiles (class FilterFiles)

> If this is ‘`on`’ (default), DDD filters files when opening execution files, core dumps, or source files, such that the selection shows only suitable files. This requires that DDD opens each file, which may take time. If this is ‘`off`’, DDD always presents all available files.

Next: Running, Previous: Navigating, Up: Top

## 5 Stopping the Program

The principal purposes of using a debugger are so that you can stop your program before it terminates; or so that, if your program runs into trouble, you can investigate and find out why.

Inside DDD, your program may stop for any of several reasons, such as a signal, a breakpoint, or reaching a new line after a DDD command such as ‘`Step`’. You may then examine and change variables, set new breakpoints or remove old ones, and then continue execution.

The inferior debuggers supported by DDD support two mechanisms for stopping a program upon specific events:

- A breakpoint makes your program stop whenever a certain point in the program is reached. For each breakpoint, you can add conditions to control in finer detail whether your program stops. Typically, breakpoints are set before running the program.
- A watchpoint is a special breakpoint that stops your program when the value of an expression changes.

Next: Watchpoints, Up: Stopping

### 5.1 Breakpoints

Next: Deleting Breakpoints, Up: Breakpoints

#### 5.1.1 Setting Breakpoints

You can set breakpoints by location or by name.

##### 5.1.1.1 Setting Breakpoints by Location

Breakpoints are set at a specific location in the program.

If the source line is visible, click with mouse button 1 on the left of the source line and then on the ‘`Break`’ button.

As a faster alternative, you can simply press mouse button 3 on the left of the source line and select the ‘`Set Breakpoint`’ item from the line popup menu.

As an even faster alternative, you can simply double-click on the left of the source line to set a breakpoint.

As yet another alternative, you can select ‘`Source Breakpoints`’. Click on the ‘`Break`’ button and enter the location.

(If you find this number of alternatives confusing, be aware that DDD users fall into three categories, which must all be supported. Novice users explore DDD and may prefer to use one single mouse button. Advanced users know how to use shortcuts and prefer popup menus. Experienced users prefer the command line interface.)

Breakpoints are indicated by a plain stop sign, or as ‘`#n`’, where n is the breakpoint number. A greyed out stop sign (or ‘`_n_`’) indicates a disabled breakpoint. A stop sign with a question mark (or ‘`?n?`’) indicates a conditional breakpoint or a breakpoint with an ignore count set.

If you set a breakpoint by mistake, use ‘`Edit Undo`’ to delete it again.

##### 5.1.1.2 Setting Breakpoints by Name

If the function name is visible, click with mouse button 1 on the function name. The function name is then copied to the argument field. Click on the ‘`Break`’ button to set a breakpoint there.

As a shorter alternative, you can simply press mouse button 3 on the function name and select the ‘`Break at`’ item from the popup menu.

As yet another alternative, you can click on ‘`Break...`’ from the Breakpoint editor (invoked through ‘`Source Breakpoints`’) and enter the function name.

##### 5.1.1.3 Setting Regexp Breakpoints

Using GDB, you can also set a breakpoint on all functions that match a given string. ‘`Break Set Breakpoints at Regexp ()`’ sets a breakpoint on all functions whose name matches the regular expression given in ‘`()`’. Here are some examples:

- To set a breakpoint on every function that starts with ‘`Xm`’, set ‘`()`’ to ‘`^Xm`’.
- To set a breakpoint on every member of class ‘`Date`’, set ‘`()`’ to ‘`^Date::`’.
- To set a breakpoint on every function whose name contains ‘`_fun`’, set ‘`()`’ to ‘`_fun`’.
- To set a breakpoint on every function that ends in ‘`_test`’, set ‘`()`’ to ‘`_test$`’.

Next: Disabling Breakpoints, Previous: Setting Breakpoints, Up: Breakpoints

#### 5.1.2 Deleting Breakpoints

To delete a visible breakpoint, click with mouse button 1 on the breakpoint. The breakpoint location is copied to the argument field. Click on the ‘`Clear`’ button to delete all breakpoints there.

If the function name is visible, click with mouse button 1 on the function name. The function name is copied to the argument field. Click on the ‘`Clear`’ button to clear all breakpoints there.

As a faster alternative, you can simply press mouse button 3 on the breakpoint and select the ‘`Delete Breakpoint`’ item from the popup menu.

As yet another alternative, you can select the breakpoint and click on ‘`Delete`’ in the Breakpoint editor (invoked through ‘`Source Breakpoints`’).

As an even faster alternative, you can simply double-click on the breakpoint while holding <Ctrl>.

Next: Temporary Breakpoints, Previous: Deleting Breakpoints, Up: Breakpoints

#### 5.1.3 Disabling Breakpoints

Rather than deleting a breakpoint or watchpoint, you might prefer to disable it. This makes the breakpoint inoperative as if it had been deleted, but remembers the information on the breakpoint so that you can enable it again later.12

To disable a breakpoint, press mouse button 3 on the breakpoint symbol and select the ‘`Disable Breakpoint`’ item from the breakpoint popup menu. To enable it again, select ‘`Enable Breakpoint`’.

As an alternative, you can select the breakpoint and click on ‘`Disable`’ or ‘`Enable`’ in the Breakpoint editor (invoked through ‘`Source Breakpoints`’.

Disabled breakpoints are indicated by a grey stop sign, or ‘`_n_`’, where n is the breakpoint number.

The ‘`Disable Breakpoint`’ item is also accessible via the ‘`Clear`’ button. Just press and hold mouse button 1 on the button to get a popup menu.

Next: Editing Breakpoint Properties, Previous: Disabling Breakpoints, Up: Breakpoints

#### 5.1.4 Temporary Breakpoints

A temporary breakpoint is immediately deleted as soon as it is reached.13

To set a temporary breakpoint, press mouse button 3 on the left of the source line and select the ‘`Set Temporary Breakpoint`’ item from the popup menu.

As a faster alternative, you can simply double-click on the left of the source line while holding <Ctrl>.

Temporary breakpoints are convenient to make the program continue up to a specific location: just set the temporary breakpoint at this location and continue execution.

The ‘`Continue Until Here`’ item from the popup menu sets a temporary breakpoint on the left of the source line and immediately continues execution. Execution stops when the temporary breakpoint is reached.

The ‘`Set Temporary Breakpoint`’ and ‘`Continue Until Here`’ items are also accessible via the ‘`Break`’ button. Just press and hold mouse button 1 on the button to get a popup menu.

Next: Breakpoint Conditions, Previous: Temporary Breakpoints, Up: Breakpoints

#### 5.1.5 Editing Breakpoint Properties

You can change all properties of a breakpoint by pressing mouse button 3 on the breakpoint symbol and select ‘`Properties`’ from the breakpoint popup menu. This will pop up a dialog showing the current properties of the selected breakpoint.

As an even faster alternative, you can simply double-click on the breakpoint.

- Click on ‘`Lookup`’ to move the cursor to the breakpoint's location.
- Click on ‘`Enable`’ to enable the breakpoint.
- Click on ‘`Disable`’ to disable the breakpoint.
- Click on ‘`Temp`’ to make the breakpoint temporary.14
- Click on ‘`Delete`’ to delete the breakpoint.

Next: Breakpoint Ignore Counts, Previous: Editing Breakpoint Properties, Up: Breakpoints

#### 5.1.6 Breakpoint Conditions

The simplest sort of breakpoint breaks every time your program reaches a specified place. You can also specify a condition for a breakpoint. A condition is just a Boolean expression in your programming language. A breakpoint with a condition evaluates the expression each time your program reaches it, and your program stops only if the condition is true.

This is the converse of using assertions for program validation; in that situation, you want to stop when the assertion is violated–that is, when the condition is false. In C, if you want to test an assertion expressed by the condition assertion, you should set the condition ‘`!assertion`’ on the appropriate breakpoint.

Break conditions can have side effects, and may even call functions in your program. This can be useful, for example, to activate functions that log program progress, or to use your own print functions to format special data structures. The effects are completely predictable unless there is another enabled breakpoint at the same address. (In that case, DDD might see the other breakpoint first and stop your program without checking the condition of this one.)

Note that breakpoint commands are usually more convenient and flexible for the purpose of performing side effects when a breakpoint is reached. See Breakpoint Commands, for details.

Next: Breakpoint Commands, Previous: Breakpoint Conditions, Up: Breakpoints

#### 5.1.7 Breakpoint Ignore Counts

A special case of a breakpoint condition is to stop only when the breakpoint has been reached a certain number of times. This is so useful that there is a special way to do it, using the ignore count of the breakpoint. Every breakpoint has an ignore count, which is an integer. Most of the time, the ignore count is zero, and therefore has no effect. But if your program reaches a breakpoint whose ignore count is positive, then instead of stopping, it just decrements the ignore count by one and continues. As a result, if the ignore count value is n, the breakpoint does not stop the next n times your program reaches it.

In the field ‘`Ignore Count`’ of the ‘`Breakpoint Properties`’ panel, you can specify the breakpoint ignore count.15

If a breakpoint has a positive ignore count and a condition, the condition is not checked. Once the ignore count reaches zero, DDD resumes checking the condition.

Next: Moving and Copying Breakpoints, Previous: Breakpoint Ignore Counts, Up: Breakpoints

#### 5.1.8 Breakpoint Commands

You can give any breakpoint (or watchpoint) a series of DDD commands to execute when your program stops due to that breakpoint. For example, you might want to print the values of certain expressions, or enable other breakpoints.16

Using the ‘`Commands`’ buttons of the ‘`Breakpoint Properties`’ panel, you can edit commands to be executed when the breakpoint is hit.

To edit breakpoint commands, click on ‘`Edit >>`’ and enter the commands in the commands editor. When done with editing, click on ‘`Edit <<`’ to close the commands editor.

Using GDB, you can also record a command sequence to be executed. To record a command sequence, follow these steps:

1. Click on ‘`Record`’ to begin the recording of the breakpoint commands.
2. Now interact with DDD. While recording, DDD does not execute commands, but simply records them to be executed when the breakpoint is hit. The recorded debugger commands are shown in the debugger console.
3. To stop the recording, click on ‘`End`’ or enter ‘`end`’ at the GDB prompt. To cancel the recording, click on ‘`Interrupt`’ or press <ESC>.
4. You can edit the breakpoint commands just recorded using ‘`Edit >>`’.

Next: Looking up Breakpoints, Previous: Breakpoint Commands, Up: Breakpoints

#### 5.1.9 Moving and Copying Breakpoints

To move a breakpoint to a different location, press mouse button 1 on the stop sign and drag it to the desired location.17 This is equivalent to deleting the breakpoint at the old location and setting a breakpoint at the new location. The new breakpoint inherits all properties of the old breakpoint, except the breakpoint number.

To copy a breakpoint to a new location, press <Shift> while dragging.

Next: Editing all Breakpoints, Previous: Moving and Copying Breakpoints, Up: Breakpoints

#### 5.1.10 Looking up Breakpoints

If you wish to lookup a specific breakpoint, select ‘`Source Breakpoints Lookup`’. After selecting a breakpoint from the list and clicking the ‘`Lookup`’ button, the breakpoint location is displayed.

As an alternative, you can enter ‘`#n`’ in the argument field, where n is the breakpoint number, and click on the ‘`Lookup`’ button to find its definition.

Next: Hardware-Assisted Breakpoints, Previous: Looking up Breakpoints, Up: Breakpoints

#### 5.1.11 Editing all Breakpoints

To view and edit all breakpoints at once, select ‘`Source Breakpoints`’. This will popup the Breakpoint Editor which displays the state of all breakpoints.

In the breakpoint editor, you can select individual breakpoints by clicking on them. Pressing <Ctrl> while clicking toggles the selection. To edit the properties of all selected breakpoints, click on ‘`Props`’.

Previous: Editing all Breakpoints, Up: Breakpoints

#### 5.1.12 Hardware-Assisted Breakpoints

Using GDB, a few more commands related to breakpoints can be invoked through the debugger console:

`hbreak position`
  Sets a hardware-assisted breakpoint at position. This command requires hardware support and some target hardware may not have this support. The main purpose of this is EPROM/ROM code debugging, so you can set a breakpoint at an instruction without changing the instruction.
`thbreak pos`
  Set a temporary hardware-assisted breakpoint at pos.

See Setting breakpoints, for details.

Next: Interrupting, Previous: Breakpoints, Up: Stopping

### 5.2 Watchpoints

You can make the program stop as soon as some variable value changes, or when some variable is read or written. This is called setting a watchpoint on a variable.18

Watchpoints have much in common with breakpoints: in particular, you can enable and disable them. You can also set conditions, ignore counts, and commands to be executed when a watched variable changes its value.

Please note: on architectures without special watchpoint support, watchpoints currently make the program execute two orders of magnitude more slowly. This is so because the inferior debugger must interrupt the program after each machine instruction in order to examine whether the watched value has changed. However, this delay can be well worth it to catch errors when you have no clue what part of your program is the culprit.

Next: Editing Watchpoint Properties, Up: Watchpoints

#### 5.2.1 Setting Watchpoints

If the variable name is visible, click with mouse button 1 on the variable name. The variable name is copied to the argument field. Otherwise, enter the variable name in the argument field. Click on the ‘`Watch`’ button to set a watchpoint there.

Using GDB and JDB 1.2, you can set different types of watchpoints. Click and hold mouse button 1 on the ‘`Watch`’ button to get a menu.

Next: Editing all Watchpoints, Previous: Setting Watchpoints, Up: Watchpoints

#### 5.2.2 Editing Watchpoint Properties

To change the properties of a watchpoint, enter the name of the watched variable in the argument field. Click and hold mouse button 1 on the ‘`Watch`’ button and select ‘`Watchpoint Properties`’.

The Watchpoint Properties panel has the same functionality as the Breakpoint Properties panel (see Editing Breakpoint Properties). As an additional feature, you can click on ‘`Print`’ to see the current value of a watched variable.

Next: Deleting Watchpoints, Previous: Editing Watchpoint Properties, Up: Watchpoints

#### 5.2.3 Editing all Watchpoints

To view and edit all watchpoints at once, select ‘`Data Watchpoints`’. This will popup the Watchpoint Editor which displays the state of all watchpoints.

The Watchpoint Editor has the same functionality as the Breakpoint Editor (see Editing all Breakpoints). As an additional feature, you can click on ‘`Print`’ to see the current value of a watched variable.

Previous: Editing all Watchpoints, Up: Watchpoints

#### 5.2.4 Deleting Watchpoints

To delete a watchpoint, enter the name of the watched variable in the argument field and click the ‘`Unwatch`’ button.

Next: Stopping X Programs, Previous: Watchpoints, Up: Stopping

### 5.3 Interrupting

If the program is already running (see Running), you can interrupt it any time by clicking the ‘`Interrupt`’ button or typing <ESC> in a DDD window.19 Using GDB, this is equivalent to sending a `SIGINT` (Interrupt) signal.

‘`Interrupt`’ and <ESC> also interrupt a running debugger command, such as printing data.

Previous: Interrupting, Up: Stopping

### 5.4 Stopping X Programs

If your program is a modal X application, DDD may interrupt it while it has grabbed the mouse pointer, making further interaction impossible—your X display will be unresponsive to any user actions.

By default, DDD will check after each interaction whether the pointer is grabbed. If the pointer is grabbed, DDD will continue the debugged program such that you can continue to use your X display.

This is how this feature works: When the program stops, DDD checks for input events such as keyboard or mouse interaction. If DDD does not receive any event within the next 5 seconds, DDD checks whether the mouse pointer is grabbed by attempting to grab and ungrab it. If this attempt fails, then DDD considers the pointer grabbed.

Unfortunately, DDD cannot determine the program that grabbed the pointer—it may be the debugged program, or another program. Consequently, you have another 10 seconds to cancel continuation before DDD continues the program automatically.

There is one situation where this fails: if you lock your X display while DDD is running, then DDD will consider a resulting pointer grab as a result of running the program—and automatically continue execution of the debugged program. Consequently, you can turn off this feature via ‘`Edit Preferences General Continue Automatically when Mouse Pointer is Frozen`’.

Up: Stopping X Programs

#### 5.4.1 Customizing Grab Checking

The grab checks are controlled by the following resources:

— Resource: checkGrabs (class CheckGrabs)

> If this is ‘`on`’ (default), DDD will check after each interaction whether the pointer is grabbed. If this is so, DDD will automatically continue execution of debugged program.

— Resource: checkGrabDelay (class CheckGrabDelay)

> The time to wait (in ms) after a debugger command before checking for a grabbed pointer. If DDD sees some pointer event within this delay, the pointer cannot be grabbed and an explicit check for a grabbed pointer is unnecessary. Default is `5000`, or 5 seconds.

— Resource: grabAction (class grabAction)

> The action to take after having detected a grabbed mouse pointer. This is a list of newline-separated commands. Default is `cont`, meaning to continue the debuggee. Other possible choices include `kill` (killing the debuggee) or `quit` (exiting DDD).

— Resource: grabActionDelay (class grabActionDelay)

> The time to wait (in ms) before taking an action due to having detected a grabbed pointer. During this delay, a working dialog pops up telling the user about imminent execution of the grab action (see the ‘`grabAction`’ resource, above). If the pointer grab is released within this delay, the working dialog pops down and no action is taken. This is done to exclude pointer grabs from sources other than the debugged program (including DDD). Default is `10000`, or 10 seconds.

Next: Examining Data, Previous: Stopping, Up: Top

## 6 Running the Program

You may start the debugged program with its arguments, if any, in an environment of your choice. You may redirect your program's input and output, debug an already running process, or kill a child process.

Next: Using the Execution Window, Up: Running

### 6.1 Starting Program Execution

To start execution of the debugged program, select ‘`Program Run`’. You will then be prompted for the arguments to pass to your program. You can either select from a list of previously used arguments or enter own arguments in the text field. Afterwards, press the ‘`Run`’ button to start execution with the selected arguments.

To run your program again, with the same arguments, select ‘`Program Run Again`’ or press the ‘`Run`’ button on the command tool. You may also enter `run`, followed by arguments at the debugger prompt instead.

When you click on ‘`Run`’, your program begins to execute immediately. See Stopping, for a discussion of how to arrange for your program to stop. Once your program has stopped, you may call functions in your program to examine data. See Examining Data, for details.

If the modification time of your symbol file has changed since the last time GDB read its symbols, GDB discards its symbol table, and reads it again. When it does this, GDB and DDD try to retain your current debugger state, such as breakpoints.

Next: Environment, Up: Starting Program Execution

#### 6.1.1 Your Program's Arguments

The arguments to your program are specified by the arguments of the ‘`run`’ command, as composed in ‘`Program Run`’.

In GDB, the arguments are passed to a shell, which expands wildcard characters and performs redirection of I/O, and thence to your program. Your `SHELL` environment variable (if it exists) specifies what shell GDB uses. If you do not define `SHELL`, GDB uses ‘`/bin/sh`’.

If you use another inferior debugger, the exact semantics on how the arguments are interpreted depend on the inferior debugger you are using. Normally, the shell is used to pass the arguments, so that you may use normal conventions (such as wildcard expansion or variable substitution) in describing the arguments.

Next: Working Directory, Previous: Arguments, Up: Starting Program Execution

#### 6.1.2 Your Program's Environment

Your program normally inherits its environment from the inferior debugger, which again inherits it from DDD, which again inherits it from its parent process (typically the shell or desktop).

In GDB, you can use the commands `set environment` and `unset environment` to change parts of the environment that affect your program. See Your program's environment, for details.

The following environment variables are set by DDD:

`DDD`
  Set to a string indicating the DDD version. By testing whether `DDD` is set, a debuggee (or inferior debugger) can determine whether it was invoked by DDD.
`TERM`
  Set to ‘`dumb`’, the DDD terminal type. This is set for the inferior debugger only.20
`TERMCAP`
  Set to `' (none), the DDD terminal capabilities.
`PAGER`
  Set to ‘`cat`’, the preferred DDD pager.

The inferior debugger, in turn, might also set or unset some environment variables.

Next: Input/Output, Previous: Environment, Up: Starting Program Execution

#### 6.1.3 Your Program's Working Directory

Your program normally inherits its working directory from the inferior debugger, which again inherits it from DDD, which again inherits it from its parent process (typically the shell or desktop).

You can change the working directory of the inferior debugger via ‘`File Change Directory`’ or via the ‘`cd`’ command of the inferior debugger.

Previous: Working Directory, Up: Starting Program Execution

#### 6.1.4 Your Program's Input and Output

By default, the program you run under DDD does input and output to the debugger console. Normally, you can redirect your program's input and/or output using shell redirections with the arguments—that is, additional arguments like ‘`< input`’ or ‘`> output`’. You can enter these shell redirections just like other arguments (see Arguments).

Warning: While input and output redirection work, you cannot use pipes to pass the output of the program you are debugging to another program; if you attempt this, DDD may wind up debugging the wrong program. See Attaching to a Process, for an alternative.

If command output is sent to the debugger console, it is impossible for DDD to distinguish between the output of the debugged program and the output of the inferior debugger.

Program output that confuses DDD includes:

- Primary debugger prompts (e.g. ‘`(gdb)` ’, ‘`(dbx)` ’ or ‘`(ladebug)` ’)
- Secondary debugger prompts (e.g. ‘`>`’)
- Confirmation prompts (e.g. ‘`(y or n)` ’)
- Prompts for more output (e.g. ‘`Press RETURN to continue`’)
- Display output (e.g. ‘`$pc = 0x1234`’)

If your program outputs any of these strings, you may encounter problems with DDD mistaking them for debugger output. These problems can easily be avoided by redirecting program I/O, for instance to the separate execution window (see Using the Execution Window).

If the inferior debugger changes the default TTY settings, for instance through a `stty` command in its initialization file, DDD may also become confused. The same applies to debugged programs which change the default TTY settings.

The behavior of the debugger console can be controlled using the following resource:

— Resource: lineBufferedConsole (class LineBuffered)

> If this is ‘`on`’ (default), each line from the inferior debugger is output on each own, such that the final line is placed at the bottom of the debugger console. If this is ‘`off`’, all lines are output as a whole. This is faster, but results in a random position of the last line.

Next: Attaching to a Process, Previous: Starting Program Execution, Up: Running

### 6.2 Using the Execution Window

By default, input and output of your program go to the debugger console. As an alternative, DDD can also invoke an execution window, where the program terminal input and output is shown.21

To activate the execution window, select ‘`Program Run in Execution Window`’.

Using the execution window has an important side effect: The output of your program no longer gets intermixed with the output of the inferior debugger. This makes it far easier for DDD to parse the debugger output correctly. See Debugger Communication, for details on the ‘`bufferGDBOutput`’ resource.

The execution window is opened automatically as soon as you start the debugged program. While the execution window is active, DDD redirects the standard input, output, and error streams of your program to the execution window. Note that the device ‘`/dev/tty`’ still refers to the debugger console, not the execution window.

You can override the DDD stream redirection by giving alternate redirection operations as arguments. For instance, to have your program read from file, but to write to the execution window, invoke your program with ‘`< file`’ as argument. Likewise, to redirect the standard error output to the debugger console, use ‘`2> /dev/tty`’ (assuming the inferior debugger and/or your UNIX shell support standard error redirection).

Up: Using the Execution Window

#### 6.2.1 Customizing the Execution Window

You can customize the DDD execution window and use a different TTY command. The command is set by ‘`Edit Preferences Helpers Execution Window`’:

— Resource: termCommand (class TermCommand)

> The command to invoke for the execution window—a TTY emulator that shows the input/output of the debugged program. A Bourne shell command to run in the separate TTY is appended to this string. The string ‘`@FONT@`’ is replaced by the name of the fixed width font used by DDD. A simple value is

>               Ddd*termCommand: xterm -fn @FONT@ -e /bin/sh -c

You can also set the terminal type:

— Resource: termType (class TermType)

> The terminal type provided by the ‘`termCommand`’ resource—that is, the value of the `TERM` environment variable to be passed to the debugged program. Default: ‘`xterm`’.

Whether the execution window is active or not, as set by ‘`Program Run in Execution Window`’, is saved using this resource:

— Resource: separateExecWindow (class Separate)

> If ‘`on`’, the debugged program is executed in a separate execution window. If ‘`off`’ (default), the debugged program is executed in the console window.

Next: Program Stop, Previous: Using the Execution Window, Up: Running

### 6.3 Attaching to a Running Process

If the debugged program is already running in some process, you can attach to this process (instead of starting a new one with ‘`Run`’).22

To attach DDD to a process, select ‘`File Attach to Process`’. You can now choose from a list of processes. Then, press the ‘`Attach`’ button to attach to the specified process.

The first thing DDD does after arranging to debug the specified process is to stop it. You can examine and modify an attached process with all the DDD commands that are ordinarily available when you start processes with ‘`Run`’. You can insert breakpoints; you can step and continue; you can modify storage. If you would rather the process continue running, you may use ‘`Continue`’ after attaching DDD to the process.

When using ‘`Attach to Process`’, you should first use ‘`Open Program`’ to specify the program running in the process and load its symbol table.

When you have finished debugging the attached process, you can use the ‘`File Detach Process`’ to release it from DDD control. Detaching the process continues its execution. After ‘`Detach Process`’, that process and DDD become completely independent once more, and you are ready to attach another process or start one with ‘`Run`’.

You can customize the list of processes shown by defining an alternate command to list processes. See ‘`Edit Preferences Helpers List Processes`’; See Customizing Attaching to Processes, for details.

Up: Attaching to a Process

#### 6.3.1 Customizing Attaching to Processes

When attaching to a process (see Attaching to a Process), DDD uses a `ps` command to get the list of processes. This command is defined by the ‘`psCommand`’ resource.

— Resource: psCommand (class PsCommand)

> The command to get a list of processes. Usually `ps`. Depending on your system, useful alternate values include `ps -ef` and `ps ux`. The first line of the output must either contain a ‘`PID`’ title, or each line must begin with a process ID.

> Note that the output of this command is filtered by DDD; a process is only shown if it can be attached to. The DDD process itself as well as the process of the inferior debugger are suppressed, too.

Next: Resuming Execution, Previous: Attaching to a Process, Up: Running

### 6.4 Program Stops

After the program has been started, it runs until one of the following happens:

- A breakpoint is reached (see Breakpoints).
- A watched value changes (see Watchpoints).
- The program is interrupted (see Interrupting).
- A signal is received (see Signals).
- Execution completes.

DDD shows the current program status in the debugger console. The current execution position is highlighted by an arrow.

If ‘`Edit Preferences General Uniconify When Ready`’ is set, DDD automatically deiconifies itself when the program stops. This way, you can iconify DDD during a lengthy computation and have it uniconify as soon as the program stops.

Next: Continuing Somewhere Else, Previous: Program Stop, Up: Running

### 6.5 Resuming Execution

#### 6.5.1 Continuing

To resume execution, at the current execution position, click on the ‘`Continue`’ button. Any breakpoints set at the current execution position are bypassed.

#### 6.5.2 Stepping one Line

To execute just one source line, click on the ‘`Step`’ button. The program is executed until control reaches a different source line, which may be in a different function. Then, the program is stopped and control returns to DDD.

Warning: If you use the ‘`Step`’ button while control is within a function that was compiled without debugging information, execution proceeds until control reaches a function that does have debugging information. Likewise, it will not step into a function which is compiled without debugging information. To step through functions without debugging information, use the ‘`Stepi`’ button (see Machine Code Execution).

In GDB, the ‘`Step`’ button only stops at the first instruction of a source line. This prevents the multiple stops that used to occur in switch statements, for loops, etc. ‘`Step`’ continues to stop if a function that has debugging information is called within the line.

Also, the ‘`Step`’ in GDB only enters a subroutine if there is line number information for the subroutine. Otherwise it acts like the ‘`Next`’ button.

#### 6.5.3 Continuing to the Next Line

To continue to the next line in the current function, click on the ‘`Next`’ button. This is similar to ‘`Step`’, but any function calls appearing within the line of code are executed without stopping.

Execution stops when control reaches a different line of code at the original stack level that was executing when you clicked on ‘`Next`’.

#### 6.5.4 Continuing Until Here

To continue running until a specific location is reached, use the ‘`Continue Until Here`’ facility from the line popup menu. See Temporary Breakpoints, for a discussion.

#### 6.5.5 Continuing Until a Greater Line is Reached

To continue until a greater line in the current function is reached, click on the ‘`Until`’ button. This is useful to avoid single stepping through a loop more than once.

‘`Until`’ is like ‘`Next`’, except that when ‘`Until`’ encounters a jump, it automatically continues execution until the program counter is greater than the address of the jump.

This means that when you reach the end of a loop after single stepping though it, ‘`until`’ makes your program continue execution until it exits the loop. In contrast, clicking on ‘`Next`’ at the end of a loop simply steps back to the beginning of the loop, which forces you to step through the next iteration.

‘`Until`’ always stops your program if it attempts to exit the current stack frame.

‘`Until`’ works by means of single instruction stepping, and hence is slower than continuing until a breakpoint is reached.

#### 6.5.6 Continuing Until Function Returns

To continue running until the current function returns, use the ‘`Finish`’ button. The returned value (if any) is printed.

Next: Stack, Previous: Resuming Execution, Up: Running

### 6.6 Continuing at a Different Address

Ordinarily, when you continue your program, you do so at the place where it stopped. You can instead continue at an address of your own choosing.

The most common occasion to use this feature is to back up—perhaps with more breakpoints set-over a portion of a program that has already executed, in order to examine its execution in more detail.

To set the execution position to the current location, use ‘`Set Execution Position`’ from the breakpoint popup menu. This item is also accessible by pressing and holding the ‘`Break/Clear`’ button.23

As a quicker alternative, you can also press mouse button 1 on the arrow and drag it to a different location.24

Moving the execution position does not change the current stack frame, or the stack pointer, or the contents of any memory location or any register other than the program counter.

Some inferior debuggers (notably GDB) allow you to set the new execution position into a different function from the one currently executing. This may lead to bizarre results if the two functions expect different patterns of arguments or of local variables. For this reason, moving the execution position requests confirmation if the specified line is not in the function currently executing.

After moving the execution position, click on ‘`Continue`’ to resume execution.

Next: Undoing Program Execution, Previous: Continuing Somewhere Else, Up: Running

### 6.7 Examining the Stack

When your program has stopped, the first thing you need to know is where it stopped and how it got there.

Each time your program performs a function call, information about the call is generated. That information includes the location of the call in your program, the arguments of the call, and the local variables of the function being called. The information is saved in a block of data called a stack frame. The stack frames are allocated in a region of memory called the call stack.

When your program stops, the DDD commands for examining the stack allow you to see all of this information.

One of the stack frames is selected by DDD and many DDD commands refer implicitly to the selected frame. In particular, whenever you ask DDD for the value of a variable in your program, the value is found in the selected frame. There are special DDD commands to select whichever frame you are interested in.

Next: Backtraces, Up: Stack

#### 6.7.1 Stack Frames

The call stack is divided up into contiguous pieces called stack frames, or frames for short; each frame is the data associated with one call to one function. The frame contains the arguments given to the function, the function's local variables, and the address at which the function is executing.

When your program is started, the stack has only one frame, that of the function `main`. This is called the initial frame or the outermost frame. Each time a function is called, a new frame is made. Each time a function returns, the frame for that function invocation is eliminated. If a function is recursive, there can be many frames for the same function. The frame for the function in which execution is actually occurring is called the innermost frame. This is the most recently created of all the stack frames that still exist.

Inside your program, stack frames are identified by their addresses. A stack frame consists of many bytes, each of which has its own address; each kind of computer has a convention for choosing one byte whose address serves as the address of the frame. Usually this address is kept in a register called the frame pointer register while execution is going on in that frame.

GDB assigns numbers to all existing stack frames, starting with zero for the innermost frame, one for the frame that called it, and so on upward. These numbers do not really exist in your program; they are assigned by GDB to give you a way of designating stack frames in GDB commands.

Next: Selecting a frame, Previous: Frames, Up: Stack

#### 6.7.2 Backtraces

DDD provides a backtrace window showing a summary of how your program got where it is. It shows one line per frame, for many frames, starting with the currently executing frame (frame zero), followed by its caller (frame one), and on up the stack.

To enable the backtrace window, select ‘`Status Backtrace`’.

Using GDB, each line in the backtrace shows the frame number and the function name. The program counter value is also shown—unless you use the GDB command ‘`set print address off`’. The backtrace also shows the source file name and line number, as well as the arguments to the function. The program counter value is omitted if it is at the beginning of the code for that line number.

Previous: Backtraces, Up: Stack

#### 6.7.3 Selecting a Frame

Most commands for examining the stack and other data in your program work on whichever stack frame is selected at the moment. Here are the commands for selecting a stack frame.25

In the backtrace window, you can select an arbitrary frame to move from one stack frame to another. Just click on the desired frame.

The ‘`Up`’ button selects the function that called the current one—that is, it moves one frame up.

The ‘`Down`’ button selects the function that was called by the current one—that is, it moves one frame down.

You can also directly type the `up` and `down` commands at the debugger prompt. Typing <Ctrl+Up> and <Ctrl+Down>, respectively, will also move you through the stack.

‘`Up`’ and ‘`Down`’ actions can be undone via ‘`Edit Undo`’.

Next: Threads, Previous: Stack, Up: Running

### 6.8 “Undoing” Program Execution

If you take a look at the ‘`Edit Undo`’ menu item after an execution command, you'll find that DDD offers you to undo execution commands just as other commands. Does this mean that DDD allows you to go backwards in time, undoing program execution as well as undoing any side-effects of your program?

Sorry—we must disappoint you. DDD cannot undo what your program did. (After a little bit of thought, you'll find that this would be impossible in general.) However, DDD can do something different: it can show previously recorded states of your program.

After “undoing” an execution command (via ‘`Edit Undo`’, or the ‘`Undo`’ button), the execution position moves back to the earlier position and displayed variables take their earlier values. Your program state is in fact unchanged, but DDD gives you a view on the earlier state as recorded by DDD.

In this so-called historic mode, most normal DDD commands that would query further information from the program are disabled, since the debugger cannot be queried for the earlier state. However, you can examine the current execution position, or the displayed variables. Using ‘`Undo`’ and ‘`Redo`’, you can move back and forward in time to examine how your program got into the present state.

To let you know that you are operating in historic mode, the execution arrow gets a dashed-line appearance (indicating a past position); variable displays also come with dashed lines. Furthermore, the status line informs you that you are seeing an earlier program state.

Here's how historic mode works: each time your program stops, DDD collects the current execution position and the values of displayed variables. Backtrace, thread, and register information is also collected if the corresponding dialogs are open. When “undoing” an execution command, DDD updates its view from this collected state instead of querying the program.

If you want to collect this information without interrupting your program—within a loop, for instance—you can place a breakpoint with an associated `cont` command (see Breakpoint Commands). When the breakpoint is hit, DDD will stop, collect the data, and execute the ‘`cont`’ command, resuming execution. Using a later ‘`Undo`’, you can step back and look at every single loop iteration.

To leave historic mode, you can use ‘`Redo`’ until you are back in the current program state. However, any DDD command that refers to program state will also leave historic mode immediately by applying to the current program state instead. For instance, ‘`Up`’ leaves historic mode immediately and selects an alternate frame in the restored current program state.

If you want to see the history of a specific variable, as recorded during program stops, you can enter the DDD command

         graph history name

This returns a list of all previously recorded values of the variable name, using array syntax. Note that name must have been displayed at earlier program stops in order to record values.

Next: Signals, Previous: Undoing Program Execution, Up: Running

### 6.9 Examining Threads

In some operating systems, a single program may have more than one thread of execution. The precise semantics of threads differ from one operating system to another, but in general the threads of a single program are akin to multiple processes—except that they share one address space (that is, they can all examine and modify the same variables). On the other hand, each thread has its own registers and execution stack, and perhaps private memory.

For debugging purposes, DDD lets you display the list of threads currently active in your program and lets you select the current thread—the thread which is the focus of debugging. DDD shows all program information from the perspective of the current thread.26

To view all currently active threads in your program, select ‘`Status Threads`’. The current thread is highlighted. Select any thread to make it the current thread.

Using JDB, additional functionality is available:

- Select a thread group to switch between viewing all threads and the threads of the selected thread group;
- Click on ‘`Suspend`’ to suspend execution of the selected threads;
- Click on ‘`Resume`’ to resume execution of the selected threads.

For more information on threads, see the JDB and GDB documentation (see Debugging programs with multiple threads).

Next: Killing the Program, Previous: Threads, Up: Running

### 6.10 Handling Signals

A signal is an asynchronous event that can happen in a program. The operating system defines the possible kinds of signals, and gives each kind a name and a number. For example, in UNIX, `SIGINT` is the signal a program gets when you type an interrupt; `SIGSEGV` is the signal a program gets from referencing a place in memory far away from all the areas in use; `SIGALRM` occurs when the alarm clock timer goes off (which happens only if your program has requested an alarm).

Some signals, including `SIGALRM`, are a normal part of the functioning of your program. Others, such as `SIGSEGV`, indicate errors; these signals are fatal (kill your program immediately) if the program has not specified in advance some other way to handle the signal. `SIGINT` does not indicate an error in your program, but it is normally fatal so it can carry out the purpose of the interrupt: to kill the program.

GDB has the ability to detect any occurrence of a signal in your program. You can tell GDB in advance what to do for each kind of signal.

Normally, DDD is set up to ignore non-erroneous signals like `SIGALRM` (so as not to interfere with their role in the functioning of your program) but to stop your program immediately whenever an error signal happens. In DDD, you can view and edit these settings via ‘`Status Signals`’.

‘`Status Signals`’ pops up a panel showing all the kinds of signals and how GDB has been told to handle each one. The settings available for each signal are:

`Stop`
  If set, GDB should stop your program when this signal happens. This also implies ‘`Print`’ being set.
`Print`
  If set, GDB should print a message when this signal happens.

  If unset, GDB should not mention the occurrence of the signal at all. This also implies ‘`Stop`’ being unset.

`Pass`
  If set, GDB should allow your program to see this signal; your program can handle the signal, or else it may terminate if the signal is fatal and not handled.

  If unset, GDB should not allow your program to see this signal.

The entry ‘`All Signals`’ is special. Changing a setting here affects all signals at once—except those used by the debugger, typically `SIGTRAP` and `SIGINT`.

To undo any changes, use ‘`Edit Undo`’. The ‘`Reset`’ button restores the saved settings.

When a signal stops your program, the signal is not visible until you continue. Your program sees the signal then, if ‘`Pass`’ is in effect for the signal in question at that time. In other words, after GDB reports a signal, you can change the ‘`Pass`’ setting in ‘`Status Signals`’ to control whether your program sees that signal when you continue.

You can also cause your program to see a signal it normally would not see, or to give it any signal at any time. The ‘`Send`’ button will resume execution where your program stopped, but immediately give it the signal shown.

On the other hand, you can also prevent your program from seeing a signal. For example, if your program stopped due to some sort of memory reference error, you might store correct values into the erroneous variables and continue, hoping to see more execution; but your program would probably terminate immediately as a result of the fatal signal once it saw the signal. To prevent this, you can resume execution using ‘`Commands Continue Without Signal`’.

Signal settings are not saved across DDD invocations, since changed signal settings are normally useful within specific projects only. Instead, signal settings are saved with the current session, using ‘`File Save Session As`’.

Previous: Signals, Up: Running

### 6.11 Killing the Program

You can kill the process of the debugged program at any time using the ‘`Kill`’ button. Killing the process is useful if you wish to debug a core dump instead of a running process. GDB ignores any core dump file while your program is running.

The ‘`Kill`’ button is also useful if you wish to recompile and relink your program, since on many systems it is impossible to modify an executable file while it is running in a process. In this case, when you next click on ‘`Run`’, GDB notices that the file has changed, and reads the symbol table again (while trying to preserve your current debugger state).

Next: Machine-Level Debugging, Previous: Running, Up: Top

## 7 Examining Data

DDD provides several means to examine data.

- The quickest way to examine variables is to move the pointer on an occurrence in the source text. The value is displayed in the source line; after a second, a popup window (called value tip) shows the variable value. This is useful for quick examination of several simple values.
- If you want to refer to variable values at a later time, you can print the value in the debugger console. This allows for displaying and examining larger data structures.
- If you want to examine complex data structures, you can display them graphically in the data window. Displays remain effective until you delete them; they are updated each time the program stops. This is useful for large dynamic structures.
- If you want to examine arrays of numeric values, you can plot them graphically in a separate plot window. The plot is updated each time the program stops. This is useful for large numeric arrays.
- Using GDB or DBX, you can also examine memory contents in any of several formats, independently of your program's data types.

Next: Printing Values, Up: Examining Data

### 7.1 Showing Simple Values using Value Tips

To display the value of a simple variable, move the mouse pointer on its name. After a second, a small window (called value tip) pops up showing the value of the variable pointed at. The window disappears as soon as you move the mouse pointer away from the variable. The value is also shown in the status line.

You can disable value tips via ‘`Edit Preferences General Automatic display of variable values as popup tips`’.

You can disable displaying variable values in the status line via ‘`Edit Preferences General Automatic display of variable values in the status line`’.

These customizations are tied to the following resources:

— Resource: valueTips (class Tips)

> Whether value tips are enabled (‘`on`’, default) or not (‘`off`’). Value tips affect DDD performance and may be distracting for some experienced users.

— Resource: valueDocs (class Docs)

> Whether the display of variable values in the status line is enabled (‘`on`’, default) or not (‘`off`’).

You can turn off value tips via ‘`Edit Preferences General Automatic Display of Variable Values`’.

Next: Displaying Values, Previous: Value Tips, Up: Examining Data

### 7.2 Printing Simple Values in the Debugger Console

The variable value can also be printed in the debugger console, making it available for future operations. To print a variable value, select the desired variable by clicking mouse button 1 on its name. The variable name is copied to the argument field. By clicking the ‘`Print`’ button, the value is printed in the debugger console. The printed value is also shown in the status line.

As a shorter alternative, you can simply press mouse button 3 on the variable name and select the ‘`Print`’ item from the popup menu.

In GDB, the ‘`Print`’ button generates a `print` command, which has several more options. See Examining Data, for GDB-specific expressions, variables, and output formats.

Next: Plotting Values, Previous: Printing Values, Up: Examining Data

### 7.3 Displaying Complex Values in the Data Window

To explore complex data structures, you can display them permanently in the data window. The data window displays selected data of your program, showing complex data structures graphically. It is updated each time the program stops.

Next: Arrays, Up: Displaying Values

#### 7.3.1 Display Basics

This section discusses how to create, manipulate, and delete displays. The essentials are:

- Click on ‘`Display`’ to display the variable in ‘`()`’.
- Click on a display to select it.
- Click on ‘`Undisplay`’ to delete the selected display.

Next: Selecting Displays, Up: Display Basics

##### 7.3.1.1 Creating Single Displays

To create a new display showing a specific variable, select the variable by clicking mouse button 1 on its name. The variable name is copied to the argument field. By clicking the ‘`Display`’ button, a new display is created in the data window. The data window opens automatically as soon as you create a display.

As a shorter alternative, you can simply press mouse button 3 on the variable name and select ‘`Display`’ from the popup menu.

As an even faster alternative, you can also double-click on the variable name.

As another alternative, you may also enter the expression to be displayed in the argument field and press the ‘`Display`’ button.

Finally, you may also type in a command at the debugger prompt:

         graph display expr [clustered] [at (x, y)]
             [dependent on display] [[now or] when in scope]

This command creates a new display showing the value of the expression expr. The optional parts have the following meaning:

`clustered`
  If given, the new display is created in a cluster. See Clustering, for a discussion.
`at (`x`,` y`)`
  If given, the new display is created at the position (x, y). Otherwise, a default position is assigned.
`dependent on` display
  If given, an edge from the display numbered or named display to the new display is created. Otherwise, no edge is created. See Dependent Values, for details.
`when in` scope
`now or when in` scope
  If ‘`when in`’ is given, the display creation is deferred until execution reaches the given scope (a function name, as in the backtrace output).

  If ‘`now or when in`’ is given, DDD first attempts to create the display immediately. The display is deferred only if display creation fails.

  If neither ‘`when in`’ suffix nor ‘`now or when in`’ suffix is given, the display is created immediately.

Next: Showing and Hiding Details, Previous: Creating Single Displays, Up: Display Basics

##### 7.3.1.2 Selecting Displays

Each display in the data window has a title bar containing the display number and the displayed expression (the display name). Below the title, the display value is shown.

You can select single displays by clicking on them with mouse button 1.

You can extend an existing selection by pressing the <Shift> key while selecting. You can also toggle an existing selection by pressing the <Shift> key while selecting already selected displays.

Single displays may also be selected by using the arrow keys <Up>, <Down>, <Left>, and <Right>.

Multiple displays are selected by pressing and holding mouse button 1 somewhere on the window background. By moving the pointer while holding the button, a selection rectangle is shown; all displays fitting in the rectangle are selected when mouse button 1 is released.

If the <Shift> key is pressed while selecting, the existing selection is extended.

By double-clicking on a display title, the display itself and all connected displays are automatically selected.

Next: Rotating Displays, Previous: Selecting Displays, Up: Display Basics

##### 7.3.1.3 Showing and Hiding Details

Aggregate values (i.e. records, structs, classes, and arrays) can be shown expanded, that is, displaying all details, or hidden, that is, displayed as ‘`{...}`’.

To show details about an aggregate, select the aggregate by clicking mouse button 1 on its name or value and click on the ‘`Show`’ button. Details are shown for the aggregate itself as well as for all contained sub-aggregates.

To hide details about an aggregate, select the aggregate by clicking mouse button 1 on its name or value and click on the ‘`Hide`’ button.

When pressing and holding mouse button 1 on the ‘`Show/Hide`’ button, a menu pops up with even more alternatives:

`Show More ()`
  Shows details of all aggregates currently hidden, but not of their sub-aggregates. You can invoke this item several times in a row to reveal more and more details of the selected aggregate.
`Show Just ()`
  Shows details of the selected aggregate, but hides all sub-aggregates.
`Show All ()`
  Shows all details of the selected aggregate and of its sub-aggregates. This item is equivalent to the ‘`Show`’ button.
`Hide ()`
  Hide all details of the selected aggregate. This item is equivalent to the ‘`Hide`’ button.

As a faster alternative, you can also press mouse button 3 on the aggregate and select the appropriate menu item.

As an even faster alternative, you can also double-click mouse button 1 on a value. If some part of the value is hidden, more details will be shown; if the entire value is shown, double-clicking will hide the value instead. This way, you can double-click on a value until you get the right amount of details.

If all details of a display are hidden, the display is called disabled; this is indicated by the string ‘`(Disabled)`’.

Displays can also be disabled or enabled via a DDD command, which you enter at the debugger prompt:

         graph disable display displays...

disables the given displays.

         graph enable display displays...

re-enables the given displays.

In both commands, displays... is either

- a space-separated list of display numbers to disable or enable, or
- a single display name. If you specify a display by name, all displays with this name will be affected.

Use ‘`Edit Undo`’ to undo disabling or enabling displays.

Next: Displaying Local Variables, Previous: Showing and Hiding Details, Up: Display Basics

##### 7.3.1.4 Rotating Displays

Arrays, structures and lists can be oriented horizontally or vertically. To change the orientation of a display, select it and then click on the ‘`Rotate`’ button.

As a faster alternative, you can also press mouse button 3 on the array and select ‘`Rotate`’ from the popup menu.

If a structure or list is oriented horizontally, DDD automatically suppresses the member names. This can be handy for saving space.

The last chosen display orientation is used for the creation of new displays. If you recently rotated an array to horizontal orientation, the next array you create will also be oriented horizontally. These settings are tied to the following resources:

— Resource: arrayOrientation (class Orientation)

> How arrays are to be oriented. Possible values are ‘`XmVERTICAL`’ (default) and ‘`XmHORIZONTAL`’.

— Resource: showMemberNames (class ShowMemberNames)

> Whether to show struct member names or not. Default is ‘`on`’.

— Resource: structOrientation (class Orientation)

> How structs are to be oriented. Possible values are ‘`XmVERTICAL`’ (default) and ‘`XmHORIZONTAL`’.

Next: Displaying Program Status, Previous: Rotating Displays, Up: Display Basics

##### 7.3.1.5 Displaying Local Variables

You can display all local variables at once by choosing ‘`Data Display Local Variables`’. When using DBX, XDB, JDB, or Perl, this displays all local variables, including the arguments of the current function. When using GDB or `pydb`, function arguments are contained in a separate display, activated by ‘`Data Display Arguments`’.

The display showing the local variables can be manipulated just like any other data display. Individual variables can be selected and dereferenced.

Next: Refreshing the Data Window, Previous: Displaying Local Variables, Up: Display Basics

##### 7.3.1.6 Displaying Program Status

You can create a display from the output of an arbitrary debugger command. By entering

         graph display `command`

the output of command is turned into a status display updated each time the program stops.

For instance, the command

         graph display `where`

creates a status display named ‘`Where`’ that shows the current backtrace.

If you are using GDB, DDD provides a panel from which you can choose useful status displays. Select ‘`Data Status Displays`’ and pick your choice from the list.

Refreshing status displays at each stop takes time; you should delete status displays as soon as you don't need them any more.

Next: Placement, Previous: Displaying Program Status, Up: Display Basics

##### 7.3.1.7 Refreshing the Data Window

The data window is automatically updated or refreshed each time the program stops. Values that have changed since the last refresh are highlighted.

However, there may be situations where you should refresh the data window explicitly. This is especially the case whenever you changed debugger settings that could affect the data format, and want the data window to reflect these settings.

You can refresh the data window by selecting ‘`Data Refresh Displays`’.

As an alternative, you can press mouse button 3 on the background of the data window and select the ‘`Refresh Displays`’ item.

Typing

         graph refresh

at the debugger prompt has the same effect.

Next: Clustering, Previous: Refreshing the Data Window, Up: Display Basics

##### 7.3.1.8 Display Placement

By default, displays are created from top to bottom—that is, each new display is placed below the downmost one. You can change this setting to left to right via ‘`Edit Preferences Data Placement Left to right`’.

This setting is tied to the following resource:
— Resource: displayPlacement (class Orientation)

> If this is ‘`XmVERTICAL`’ (default), DDD places each new independent display below the downmost one. If this is ‘`XmHORIZONTAL`’, each new independent display is placed on the right of the rightmost one.

Note that changing the placement of new displays also affects the placement of dependent displays (see Dependent Values). In top to bottom mode, dependent displays are created on the right of the originating display; in left to right mode, dependent displays are created on the below the originating display.

Next: Creating Multiple Displays, Previous: Placement, Up: Display Basics

##### 7.3.1.9 Clustering Displays

If you examine several variables at once, having a separate display for each of them uses a lot of screen space. This is why DDD supports clusters. A cluster merges several logical data displays into one physical display, saving screen space.

There are two ways to create clusters:

- You can create clusters manually. This is done by selecting the displays to be clustered and choosing ‘`Undisp Cluster ()`’. This creates a new cluster from all selected displays. If an already existing cluster is selected, too, the selected displays will be clustered into the selected cluster.
- You can create a cluster automatically for all independent data displays, such that all new data displays will automatically be clustered, too. This is achieved by enabling ‘`Edit Preferences Data Placement clustered`’.

Displays in a cluster can be selected and manipulated like parts of an ordinary display; in particular, you can show and hide details, or dereference pointers. However, edges leading to clustered displays can not be shown, and you must either select one or all clustered displays.

Disabling a cluster is called unclustering, and again, there are two ways of doing it:

- You can uncluster displays manually, by selecting the cluster and choosing ‘`Undisp Uncluster ()`’.
- You can uncluster all current and future displays by disabling ‘`Edit Preferences Data Placement clustered`’.

Next: Editing all Displays, Previous: Clustering, Up: Display Basics

##### 7.3.1.10 Creating Multiple Displays

To display several successive objects of the same type (a section of an array, or an array of dynamically determined size), you can use the notation ‘`from..to`’ in display expressions.

from and to are numbers that denote the first and last expression to display. Thus,

         graph display argv[0..9]

creates 10 new displays for ‘`argv[0]`’, ‘`argv[1]`’, ..., ‘`argv[9]`’. The displays are clustered automatically (see Clustering), such that you can easily handle the set just like an array.

The ‘`from..to`’ notation can also be used multiple times. For instance,

         graph display 1..5 * 1..5

creates a handy small multiplication table.

The ‘`from..to`’ notation creates several displays, which takes time to create and update. If you want to display only a part of an array, array slices are a more efficient way. See Array Slices, for a discussion.

Next: Deleting Displays, Previous: Creating Multiple Displays, Up: Display Basics

##### 7.3.1.11 Editing all Displays

You can view the state of all displays by selecting ‘`Data Displays`’. This invokes the Display Editor.

The Display Editor shows the properties of each display, using the following fields:

‘`Num`’
  The display number.
‘`Expression`’
  The displayed expression.
‘`State`’
  One of
  ‘`enabled`’
    Normal state.
  ‘`disabled`’
    Disabled; all details are hidden. Use ‘`Show`’ to enable.
  ‘`not active`’
    Out of scope.
  ‘`deferred`’
    Will be created as soon as its ‘`Scope`’ is reached (see Creating Single Displays).
  ‘`clustered`’
    Part of a cluster (see Clustering). Use ‘`Undisp Uncluster`’ to uncluster.
  ‘`alias of display`’
    A suppressed alias of display display (see Shared Structures).
‘`Scope`’
  The scope in which the display was created. For deferred displays, this is the scope in which the display will be created.
‘`Address`’
  The address of the displayed expression. Used for resolving aliases (see Shared Structures).

Previous: Editing all Displays, Up: Display Basics

##### 7.3.1.12 Deleting Displays

To delete a single display, select its title or value and click on the ‘`Undisp`’ button. As an alternative, you can also press mouse button 3 on the display and select the ‘`Undisplay`’ item.

When a display is deleted, its immediate ancestors and descendants are automatically selected, so that you can easily delete entire graphs.

If you have selected only part of a display, clicking on the ‘`Undisp`’ button allows you to suppress this part—by applying the Suppress Values theme on the part. You'll be asked for confirmation first. See Using Data Themes, for details.

To delete several displays at once, use the ‘`Undisp`’ button in the Display Editor (invoked via ‘`Data Displays`’). Select any number of display items in the usual way and delete them by pressing ‘`Undisp`’.

As an alternative, you can also use a DDD command:

         graph undisplay displays...

Here, displays... is either

- a space-separated list of display numbers to disable or enable, or
- a single display name. If you specify a display by name, all displays with this name will be affected.

If you are using stacked windows, deleting the last display from the data window also automatically closes the data window. (You can change this via ‘`Edit Preferences Data Close data window when deleting last display`’.)

If you deleted a display by mistake, use ‘`Edit Undo`’ to re-create it.

Finally, you can also cut, copy, and paste displays using the ‘`Cut`’, ‘`Copy`’, and ‘`Paste`’ items from the ‘`Edit`’ menu. The clipboard holds the commands used to create the displays; ‘`Paste`’ inserts the display commands in the debugger console. This allows you to save displays for later usage or to copy displays across multiple DDD instances.

Next: Assignment, Previous: Display Basics, Up: Displaying Values

#### 7.3.2 Arrays

DDD has some special features that facilitate handling of arrays.

Next: Repeated Values, Up: Arrays

##### 7.3.2.1 Array Slices

It is often useful to print out several successive objects of the same type in memory; a slice (section) of an array, or an array of dynamically determined size for which only a pointer exists in the program.

Using DDD, you can display slices using the ‘`from..to`’ notation (see Creating Multiple Displays). But this requires that you already know from and to; it is also inefficient to create several single displays. If you use GDB, you have yet another alternative.

Using GDB, you can display successive objects by referring to a contiguous span of memory as an artificial array, using the binary operator ‘`@`’. The left operand of ‘`@`’ should be the first element of the desired array and be an individual object. The right operand should be the desired length of the array. The result is an array value whose elements are all of the type of the left argument. The first element is actually the left argument; the second element comes from bytes of memory immediately following those that hold the first element, and so on.

Here is an example. If a program says

         int *array = (int *) malloc (len * sizeof (int));

you can print the contents of `array` with

         print array[0]@len

and display the contents with

         graph display array[0]@len

The general form of displaying an array slice is thus

         graph display array[first]@nelems

where array is the name of the array to display, first is the index of the first element, and nelems is the number of elements to display.

The left operand of ‘`@`’ must reside in memory. Array values made with ‘`@`’ in this way behave just like other arrays in terms of subscripting, and are coerced to pointers when used in expressions.

Next: Arrays as Tables, Previous: Array Slices, Up: Arrays

##### 7.3.2.2 Repeated Values

Using GDB, an array value that is repeated 10 or more times is displayed only once. The value is shown with a ‘`<nx>`’ postfix added, where n is the number of times the value is repeated. Thus, the display ‘`0x0 <30x>`’ stands for 30 array elements, each with the value ‘`0x0`’. This saves a lot of display space, especially with homogeneous arrays.

The default GDB threshold for repeated array values is 10. You can change it via ‘`Edit GDB Settings Threshold for repeated print elements`’. Setting the threshold to `0` will cause GDB (and DDD) to display each array element individually. Be sure to refresh the data window via ‘`Data Refresh Displays`’ after a change in GDB settings.

You can also configure DDD to display each array element individually:

— Resource: expandRepeatedValues (class ExpandRepeatedValues)

> GDB can print repeated array elements as ‘`value <repeated n times>`’. If ‘`expandRepeatedValues`’ is ‘`on`’, DDD will display n instances of value instead. If ‘`expandRepeatedValues`’ is ‘`off`’ (default), DDD will display value with ‘`<nx>`’ appended to indicate the repetition.

Previous: Repeated Values, Up: Arrays

##### 7.3.2.3 Arrays as Tables

By default, DDD lays out two-dimensional arrays as tables, such that all array elements are aligned with each other.27 To disable this feature, unset ‘`Edit Preferences Data Display Two-Dimensional Arrays as Tables`’. This is tied to the following resource:

— Resource: align2dArrays (class Align2dArrays)

> If ‘`on`’ (default), DDD lays out two-dimensional arrays as tables, such that all array elements are aligned with each other. If ‘`off`’, DDD treats a two-dimensional array as an array of one-dimensional arrays, each aligned on its own.

Next: Examining Structures, Previous: Arrays, Up: Displaying Values

#### 7.3.3 Assignment to Variables

During program execution, you can change the values of arbitrary variables.28

To change the value of a variable, enter its name in ‘`()`’—for instance, by selecting an occurrence or a display. Then, click on the ‘`Set`’ button. In a dialog, you can edit the variable value at will; clicking the ‘`OK`’ or ‘`Apply`’ button commits your change and assigns the new value to the variable.

To change a displayed value, you can also select ‘`Set Value`’ menu from the data popup menu,

If you made a mistake, you can use ‘`Edit Undo`’ to re-set the variable to its previous value.

Next: Customizing Displays, Previous: Assignment, Up: Displaying Values

#### 7.3.4 Examining Structures

Besides displaying simple values, DDD can also visualize the Dependencies between values—especially pointers and other references that make up complex data structures.

Next: Dereferencing Pointers, Up: Examining Structures

##### 7.3.4.1 Displaying Dependent Values

Dependent displays are created from an existing display. The dependency is indicated by an edge leading from the originating display to the dependent display.

To create a dependent display, select the originating display or display part and enter the dependent expression in the ‘`():`’ argument field. Then click on the ‘`Display`’ button.

Using dependent displays, you can investigate the data structure of a tree for example and lay it out according to your intuitive image of the tree data structure.

By default, DDD does not recognize shared data structures (i.e. a data object referenced by multiple other data objects). See Shared Structures, for details on how to examine such structures.

Next: Shared Structures, Previous: Dependent Values, Up: Examining Structures

##### 7.3.4.2 Dereferencing Pointers

There are special shortcuts for creating dependent displays showing the value of a dereferenced pointer. This allows for rapid examination of pointer-based data structures.

To dereference a pointer, select the originating pointer value or name and click on the ‘`Disp *`’ button. A new display showing the dereferenced pointer value is created.

As a faster alternative, you can also press mouse button 3 on the originating pointer value or name and select the ‘`Display *`’ menu item.

As an even faster alternative, you can also double-click mouse button 1 on the originating pointer value or name. If you press <Ctrl> while double-clicking, the display will be dereferenced in place–that is, it will be replaced by the dereferenced display.

The ‘`Display *()`’ function is also accessible by pressing and holding the ‘`Display`’ button.

Next: Display Shortcuts, Previous: Dereferencing Pointers, Up: Examining Structures

##### 7.3.4.3 Shared Structures

By default, DDD does not recognize shared data structures—that is, a data object referenced by multiple other data objects. For instance, if two pointers ‘`p1`’ and ‘`p2`’ point at the same data object ‘`d`’, the data displays ‘`d`’, ‘`*p1`’, and ‘`*p2`’ will be separate, although they denote the same object.

DDD provides a special mode which makes it detect these situations. DDD recognizes if two or more data displays are stored at the same physical address, and if this is so, merges all these aliases into one single data display, the original data display. This mode is called Alias Detection; it is enabled via ‘`Data Detect Aliases`’.

When alias detection is enabled, DDD inquires the memory location (the address) of each data display after each program step. If two displays have the same address, they are merged into one. More specifically, only the one which has least recently changed remains (the original data display); all other aliases are suppressed, i.e. completely hidden. The edges leading to the aliases are replaced by edges leading to the original data display.

An edge created by alias detection is somewhat special: rather than connecting two displays directly, it goes through an edge hint, describing an arc connecting the two displays and the edge hint.

Each edge hint is a placeholder for a suppressed alias; selecting an edge hint is equivalent to selecting the alias. This way, you can easily delete display aliases by simply selecting the edge hint and clicking on ‘`Undisp`’.

To access suppressed display aliases, you can also use the Display Editor. Suppressed displays are listed in the Display Editor as aliases of the original data display. Via the Display Editor, you can select, change, and delete suppressed displays.

Suppressed displays become visible again as soon as

- alias detection is disabled,
- their address changes such that they are no more aliases, or
- the original data display is deleted, such that the least recently changed alias becomes the new original data display.

Please note the following caveats with alias detection:

- Alias detection requires that the current programming language provides a means to determine the address of an arbitrary data object. Currently, only C, C++, and Java are supported.
- Some inferior debuggers (for instance, SunOS DBX) produce incorrect output for address expressions. Given a pointer p, you may verify the correct function of your inferior debugger by comparing the values of p and ‘`&p`’ (unless p actually points to itself). You can also examine the data display addresses, as shown in the Display Editor.
- Alias detection slows down DDD slightly, which is why you can turn it off. You may consider to enable it only at need—for instance, while examining some complex data structure—and disable it while examining control flow (i.e., stepping through your program). DDD will automatically restore edges and data displays when switching modes.

Alias detection is controlled by the following resources:

— Resource: deleteAliasDisplays (class DeleteAliasDisplays)

> If this is ‘`on`’ (default), the ‘`Undisplay ()`’ button also deletes all aliases of the selected displays. If this is ‘`off`’, only the selected displays are deleted; the aliases remain, and one of the aliases will be unsuppressed.

— Resource: detectAliases (class DetectAliases)

> If ‘`on`’ (default), DDD attempts to recognize shared data structures. If ‘`off`’, shared data structures are not recognized.

— Resource: typedAliases (class TypedAliases)

> If ‘`on`’ (default), DDD requires structural equivalence in order to recognize shared data structures. If this is ‘`off`’, two displays at the same address are considered aliases, regardless of their structure.

Previous: Shared Structures, Up: Examining Structures

##### 7.3.4.4 Display Shortcuts

DDD maintains a shortcut menu of frequently used display expressions. This menu is activated

- by pressing and holding the ‘`Display`’ button, or
- by pressing mouse button 3 on some display and selecting ‘`New Display`’, or
- by pressing <Shift> and mouse button 3 on some display.

By default, the shortcut menu contains frequently used base conversions.

The ‘`Other`’ entry in the shortcut menu lets you create a new display that extends the shortcut menu.

As an example, assume you have selected a display named ‘`date_ptr`’. Selecting ‘`Display Other`’ pops up a dialog that allows you to enter a new expression to be displayed—for instance, you can cast the display ‘`date_ptr`’ to a new display ‘`(char *)date_ptr`’. If the ‘`Include in ‘`New Display`’ Menu`’ toggle was activated, the shortcut menu will then contain a new entry ‘`Display (char *)()`’ that will cast any selected display display to ‘`(char *)display`’. Such shortcuts can save you a lot of time when examining complex data structures.

You can edit the contents of the ‘`New Display`’ menu by selecting its ‘`Edit Menu`’ item. This pops up the Shortcut Editor containing all shortcut expressions, which you can edit at leisure. Each line contains the expression for exactly one menu item. Clicking on ‘`Apply`’ re-creates the ‘`New Display`’ menu from the text. If the text is empty, the ‘`New Display`’ menu will be empty, too.

DDD also allows you to specify individual labels for user-defined buttons. You can write such a label after the expression, separated by ‘`//`’. This feature is used in the default contents of the GDB ‘`New Display`’ menu, where each of the base conversions has a label:

         /t ()   // Convert to Bin
         /d ()   // Convert to Dec
         /x ()   // Convert to Hex
         /o ()   // Convert to Oct

Feel free to add other conversions here. DDD supports up to 20 ‘`New Display`’ menu items.

The shortcut menu is controlled by the following resources:

— Resource: dbxDisplayShortcuts (class DisplayShortcuts)

> A newline-separated list of display expressions to be included in the ‘`New Display`’ menu for DBX.

> If a line contains a label delimiter29, the string before the delimiter is used as expression, and the string after the delimiter is used as label. Otherwise, the label is ‘`Display expression`’. Upon activation, the string ‘`()`’ in expression is replaced by the name of the currently selected display.

— Resource: gdbDisplayShortcuts (class DisplayShortcuts)

> A newline-separated list of display expressions to be included in the ‘`New Display`’ menu for GDB. See the description of ‘`dbxDisplayShortcuts`’, above.

— Resource: jdbDisplayShortcuts (class DisplayShortcuts)

> A newline-separated list of display expressions to be included in the ‘`New Display`’ menu for JDB. See the description of ‘`dbxDisplayShortcuts`’, above.

— Resource: perlDisplayShortcuts (class DisplayShortcuts)

> A newline-separated list of display expressions to be included in the ‘`New Display`’ menu for Perl. See the description of ‘`dbxDisplayShortcuts`’, above.

— Resource: bashDisplayShortcuts (class DisplayShortcuts)

> A newline-separated list of display expressions to be included in the ‘`New Display`’ menu for Bash. See the description of ‘`dbxDisplayShortcuts`’, above.

— Resource: pydbDisplayShortcuts (class DisplayShortcuts)

> A newline-separated list of display expressions to be included in the ‘`New Display`’ menu for `pydb`. See the description of ‘`dbxDisplayShortcuts`’, above.

— Resource: xdbDisplayShortcuts (class DisplayShortcuts)

> A newline-separated list of display expressions to be included in the ‘`New Display`’ menu for XDB. See the description of ‘`dbxDisplayShortcuts`’, above.

Next: Layouting the Graph, Previous: Examining Structures, Up: Displaying Values

#### 7.3.5 Customizing Displays

Next: Applying Data Themes to Several Values, Up: Customizing Displays

##### 7.3.5.1 Using Data Themes

DDD provides a simple method to customize displays. DDD comes with a number of visual modifiers, called data themes.

Each theme modifies a particular aspect of a data display. It can be applied to individual displays or to a number of displays. The themes installed with DDD include:

‘`Small Titles`’
  If enabled, display titles in a smaller font.
‘`Small Values`’
  Apply this theme to display values in a smaller font.
‘`Tiny Values`’
  If enabled, display values in a tiny font. This could be combined with a pattern like `*\[*\]` to make all array members tiny. Apply this theme to display values in a tiny font.
‘`Suppress Values`’
  If enabled, the given value will be suppressed. This should be combined with a pattern like `*->X` to suppress all members named `X'. Apply this theme to display values not at all.
‘`Red Background`’
  Use this with a self-defined button associated with the command `graph apply red.vsl "()"`
‘`Red nil pointers`’
  If enabled, show nil pointers in red.
‘`Green background`’
  Use this with a self-defined button associated with the command `graph apply green.vsl "()"`.
‘`Intel x86 flag bits and registers`’
  To use this theme, set up some data buttons like this:

                   Ddd*dataButtons: \
                   graph display ($eflags & 1) != 0 // c\n\
                   graph display ($eflags & 64) != 0 // z\n\
                   graph display ($eflags & 128) != 0 // s\n\
                   graph display ($eflags & 1024) != 0 // d\n\
                   graph display ($eflags & 2048) != 0 // o\n\
                   graph display $eax & 255 // al\n\
                   graph display $eax >> 8 & 255 // ah\n\
                   graph display $eax & 65535 // ax\n\
                   graph display $ebx & 255 // bl\n\
                   graph display $ebx >> 8 & 255 // bh\n\
                   graph display $ebx & 65535 // bx\n\
                   graph display $ecx & 255 // cl\n\
                   graph display $ecx >> 8 & 255 // ch\n\
                   graph display $ecx & 65535 // cx\n\
                   graph display $edx & 255 // dl\n\
                   graph display $edx >> 8 & 255 // dh\n\
                   graph display $edx & 65535 // dx

  Whenever the these displays is shown, the title will be replaced by a more intuitive title like “carry”, or “zero” for one of the flag bits and “al” “ax”, etc. for one of the registers.

Each of these themes can be applied for specific displays.

To apply a theme on a display,

1. Press mouse button 3 on the display.
2. Select ‘`Theme`’
3. Select the theme to apply.

For instance, to display the variable `s` in a tiny font, click mouse button 3 on the display of `s`, and select ‘`Theme Tiny Values Apply`’.

To unapply a theme, just click on ‘`Undo`’ (if you just applied it) or repeat the sequence as above.

Next: Editing Themes, Previous: Using Data Themes, Up: Customizing Displays

##### 7.3.5.2 Applying Data Themes to Several Values

Whenever you want to apply a theme on a struct member or an array element, you will be asked whether to

- apply the theme on the single value only, or
- apply the theme on all similar values.

Suppose, for instance, that you don't want to see ‘`vptr`’ members anymore. Then you'd apply the theme Suppress Values on all similar values.

On the other hand, if you want to highlight one single value only, you'd apply the theme Red Background on only one single value.

If you find this confirmation annoying, you can define a command button which directly applies the theme. See Defining Commands, for details on defining commands.

Applying and unapplying themes is associated with the following commands:

         graph apply theme name pattern

applies the theme name on pattern.

         graph unapply theme name pattern

unapplies the theme name on pattern.

         graph toggle theme name pattern

applies the theme name on pattern if it was not already applied, and unapplies it otherwise.

Next: Writing Data Themes, Previous: Applying Data Themes to Several Values, Up: Customizing Displays

##### 7.3.5.3 Editing Themes

Each theme can be globally activated or not. If a theme is activated, it is applied to all expressions that match its pattern.

Normally, these patterns are automatically maintained by simply selecting the themes for the individual displays. However, you can also edit patterns directly.

Patterns are separated by ‘`;`’ and contain shell-like metacharacters:

- ‘`*`’ matches any sequence of characters.
- ‘`?`’ matches any single character.
- ‘`[set]`’ matches any character in set. Character ranges can be expressed using from-to: ‘`[0-9a-zA-Z_]`’ is the set of characters allowed in C characters.
- ‘`[!set]`’ matches any character not in set.
- To suppress the special syntactic significance of any metacharacter\n\ and match the character exactly, precede it with ‘`\`’ (backslash).
- To suppress the syntactic significance of all metacharacters,\n\ enclose the pattern in double or single quotes.\n\

To edit the set of themes, invoke ‘`Data Themes`’.

To apply changes you made to the themes, click on ‘`Apply`’. To revert the themes to the last saved, click on ‘`Reset`’.

Next: Display Resources, Previous: Editing Themes, Up: Customizing Displays

##### 7.3.5.4 Writing Data Themes

You can write your own data themes, customizing the display to match your need. See Top, for details.

Next: VSL Resources, Previous: Writing Data Themes, Up: Customizing Displays

##### 7.3.5.5 Display Resources

You can use these resources to control display appearance:

— Resource: autoCloseDataWindow (class AutoClose)

> If this is ‘`on`’ (default) and DDD is in stacked window mode, deleting the last display automatically closes the data window. If this is ‘`off`’, the data window stays open even after deleting the last display.

— Resource: bumpDisplays (class BumpDisplays)

> If some display d changes size and this resource is ‘`on`’ (default), DDD assigns new positions to displays below and on the right of d such that the distance between displays remains constant. If this is ‘`off`’, other displays are not rearranged.

— Resource: clusterDisplays (class ClusterDisplays)

> If ‘`on`’, new independent data displays will automatically be clustered. Default is ‘`off`’, meaning to leave new displays unclustered.

— Resource: hideInactiveDisplays (class HideInactiveDisplays)

> If some display gets out of scope and this resource is ‘`on`’ (default), DDD removes it from the data display. If this is ‘`off`’, it is simply disabled.

— Resource: showBaseDisplayTitles (class ShowDisplayTitles)

> Whether to assign titles to base (independent) displays or not. Default is ‘`on`’.

— Resource: showDependentDisplayTitles (class ShowDisplayTitles)

> Whether to assign titles to dependent displays or not. Default is ‘`off`’.

— Resource: suppressTheme (class Theme)

> The theme to apply when selecting ‘`Undisp`’ on a data value. Default is `suppress.vsl`.

— Resource: themes (class Themes)

> A newline-separated list of themes. Each theme has the format name, tabulator character, pattern.

Previous: Display Resources, Up: Customizing Displays

##### 7.3.5.6 VSL Resources

The following resources control the VSL interpreter:

— Resource: vslBaseDefs (class VSLDefs)

> A string with additional VSL definitions that are appended to the builtin VSL library. This resource is prepended to the ‘`vslDefs`’ resource below and set in the DDD application defaults file; don't change it.

— Resource: vslDefs (class VSLDefs)

> A string with additional VSL definitions that are appended to the builtin VSL library. The default value is an empty string. This resource can be used to override specific VSL definitions that affect the data display. The preferred method, though, is to write a specific data theme (see Writing Data Themes).

— Resource: vslLibrary (class VSLLibrary)

> The VSL library to use. ‘`builtin`’ (default) means to use the built-in library, any other value is used as file name.

— Resource: vslPath (class VSLPath)

> A colon-separated list of directories to search for VSL include files. The following directory names are special:

> - The special directory name ‘`user_themes`’ stands for your individual theme directory, typically `~/.ddd/themes/`.
> - The special directory name ‘`ddd_themes`’ stands for the installed theme directory, typically `/usr/local/share/ddd-3.3.12/themes/`.
> Default is ‘`user_themes:ddd_themes:.`’, which means that DDD first searches your theme directory, followed by the system directory and the current directory.

If your DDD source distribution is installed in `/opt/src`, you can use the following settings to read the VSL library from `/home/joe/ddd.vsl`:

         Ddd*vslLibrary: /home/joe/ddd.vsl
         Ddd*vslPath:    user_themes:.:/opt/src/ddd/ddd:/opt/src/ddd/vsllib

VSL include files referenced by `/home/joe/ddd.vsl` are searched first in the current directory `.`, then in your theme directory, then in `/opt/src/ddd/ddd/`, and then in `/opt/src/ddd/vsllib/`.

Instead of supplying another VSL library, it is often easier to specify some minor changes to the built-in library (see Writing Data Themes).

Next: Printing the Graph, Previous: Customizing Displays, Up: Displaying Values

#### 7.3.6 Layouting the Graph

If you have several displays at once, you may wish to arrange them according to your personal preferences. This section tells you how you can do this.

Next: Scrolling Data, Up: Layouting the Graph

##### 7.3.6.1 Moving Displays

From time to time, you may wish to move displays at another place in the data window. You can move a single display by pressing and holding mouse button 1 on the display title. Moving the pointer while holding the button causes all selected displays to move along with the pointer.

Edge hints can be selected and moved around like other displays. If an arc goes through the edge hint, you can change the shape of the arc by moving the edge hint around.

For fine-grain movements, selected displays may also be moved using the arrow keys. Pressing <Shift> and an arrow key moves displays by single pixels. Pressing <Ctrl> and arrow keys moves displays by grid positions.

Next: Aligning Displays, Previous: Moving Displays, Up: Layouting the Graph

##### 7.3.6.2 Scrolling Data

If the data window becomes too small to hold all displays, scroll bars are created. If your DDD is set up to use panners instead, a panner is created in the lower right edge. When the panner is moved around, the window view follows the position of the panner.

To change from scroll bars to panners, use ‘`Edit Startup Data Scrolling`’ and choose either ‘`Panner`’ or ‘`Scrollbars`’. This setting is tied to the following resource:

— Resource: pannedGraphEditor (class PannedGraphEditor)

> The control to scroll the graph.

> - If this is ‘`on`’, an Athena panner is used (a kind of two-directional scrollbar).
> - If this is ‘`off`’ (default), two M*tif scrollbars are used.

> See Options, for the `--scrolled-graph-editor` and `--panned-graph-editor` options.

Next: Automatic Layout, Previous: Scrolling Data, Up: Layouting the Graph

##### 7.3.6.3 Aligning Displays

You can align all displays on the nearest grid position by selecting ‘`Data Align on Grid`’. This is useful for keeping edges strictly horizontal or vertical.

You can enforce alignment by selecting ‘`Edit Preferences Data Auto-align Displays on Nearest Grid Point`’. If this feature is enabled, displays can be moved on grid positions only.

Next: Rotating the Graph, Previous: Aligning Displays, Up: Layouting the Graph

##### 7.3.6.4 Automatic Layout

You can layout the entire graph as a tree by selecting ‘`Data Layout Graph`’. The layout direction is determined from the display placement (see Placement) and from the last rotation (see Rotating the Graph).

Layouting the graph may introduce edge hints; that is, edges are no more straight lines, but lead to an edge hint and from there to their destination. Edge hints can be moved around like arbitrary displays.

To enable a more compact layout, you can set the ‘`Edit Preferences Data Compact Layout`’ option. This realizes an alternate layout algorithm, where successors are placed next to their parents. This algorithm is suitable for homogeneous data structures only.

You can enforce layout by setting ‘`Edit Preferences Data Automatic Layout`’. If automatic layout is enabled, the graph is layouted after each change.

Previous: Automatic Layout, Up: Layouting the Graph

##### 7.3.6.5 Rotating the Graph

You can rotate the entire graph clockwise by 90 degrees by selecting ‘`Data Rotate Graph`’. You may need to layout the graph after rotating it; See Automatic Layout, for details.

Previous: Layouting the Graph, Up: Displaying Values

#### 7.3.7 Printing the Graph

DDD allows for printing the graph picture on PostScript printers or into files. This is useful for documenting program states.

To print the graph on a PostScript printer, select ‘`File Print Graph`’. Enter the printing command in the ‘`Print Command`’ field. Click on the ‘`OK`’ or the ‘`Apply`’ button to start printing.

As an alternative, you may also print the graph in a file. Click on the ‘`File`’ button and enter the file name in the ‘`File Name`’ field. Click on the ‘`Print`’ button to create the file.

When the graph is printed in a file, two formats are available:

- ‘`PostScript`’—suitable for enclosing the graph in another document;
- ‘`FIG`’—suitable for post-processing, using the `xfig` graphic editor, or for conversion into other formats (among others, IBMGL, TeX, PIC), using the `transfig` or `fig2dev` programs.

Please note the following caveats related to printing graphs:

- If any displays were selected when invoking the ‘`Print`’ dialog, the option ‘`Selected Only`’ is set. This makes DDD print only the selected displays.
- The ‘`Color`’, ‘`Orientation`’, and ‘`Paper Size`’ options are meaningful for PostScript only.

These settings are tied to the following resources:

— Resource: printCommand (class PrintCommand)

> The command to print a PostScript file. Usually ‘`lp`’ or ‘`lpr`’.

— Resource: paperSize (class PaperSize)

> The paper size used for printing, in format ‘`width x height`’. The default is ISO A4 format, or ‘`210mm x 297mm`’.

Next: Examining Memory, Previous: Displaying Values, Up: Examining Data

### 7.4 Plotting Values

If you have huge amounts of numerical data to examine, a picture often says more than a thousand numbers. Therefore, DDD allows you to draw numerical values in nice 2-D and 3-D plots.

Next: Plot Appearance, Up: Plotting Values

#### 7.4.1 Plotting Arrays

Basically, DDD can plot two types of numerical values:

- One-dimensional arrays. These are drawn in a 2-D x/y space, where x denotes the array index, and y the element value.
- Two-dimensional arrays. These are drawn in a 3-D x/y/z space, where x and y denote the array indexes, and z the element value.

To plot a fixed-size array, select its name by clicking mouse button 1 on an occurrence. The array name is copied to the argument field. By clicking the ‘`Plot`’ button, a new display is created in the data window, followed by a new top-level window containing the value plot.

To plot a dynamically sized array, you must use an array slice (see Array Slices). In the argument field, enter

         array[first]@nelems

where array is the name of the array to display, first is the index of the first element, and nelems is the number of elements to display. Then, click on ‘`Plot`’ to start the plot.

To plot a value, you can also enter a command at the debugger prompt:

         graph plot expr

works like ‘`graph display expr`’ (and takes the same arguments; see Creating Single Displays), but the value is additionally shown in the plot window.

Each time the value changes during program execution, the plot is updated to reflect the current values. The plot window remains active until you close it (via ‘`File Close`’) or until the associated display is deleted.

Next: Scalars and Composites, Previous: Plotting Arrays, Up: Plotting Values

#### 7.4.2 Changing the Plot Appearance

The actual drawing is not done by DDD itself. Instead, DDD relies on an external `gnuplot` program to create the drawing.

DDD adds a menu bar to the Gnuplot plot window that lets you influence the appearance of the plot:

- The ‘`View`’ menu toggles optional parts of the plot, such as border lines or a background grid.
- The ‘`Plot`’ menu changes the plotting style. The ‘`3-D Lines`’ option is useful for plotting two-dimensional arrays.
- The ‘`Scale`’ menu allows you to enable logarithmic scaling and to enable or disable the scale tics.
- The ‘`Contour`’ menu adds contour lines to 3-D plots.

In a 3-D plot, you can use the scroll bars to change your view position. The horizontal scroll bar rotates the plot around the z axis, that is, to the left and right. The vertical scroll bar rotates the plot around the y axis, that is, up and down.

You can also resize the plot window as desired.

Next: Plotting Histories, Previous: Plot Appearance, Up: Plotting Values

#### 7.4.3 Plotting Scalars and Composites

Besides plotting arrays, DDD also allows you to plot scalars (simple numerical values). This works just like plotting arrays—you select the numerical variable, click on ‘`Plot`’, and here comes the plot. However, plotting a scalar is not very exciting. A plot that contains nothing but a scalar simply draws the scalar's value as a y constant—that is, a horizontal line.

So why care about scalars at all? DDD allows you to combine multiple values into one plot. The basic idea is: if you want to plot something that is neither an array nor a scalar, DDD takes all numerical sub-values it can find and plots them all together in one window. For instance, you can plot all local variables by selecting ‘`Data Display Local Variables`’, followed by ‘`Plot`’. This will create a plot containing all numerical values as found in the current local variables. Likewise, you can plot all numeric members contained in a structure by selecting it, followed by ‘`Plot`’.

If you want more control about what to include in a plot and what not, you can use display clusters (see Clustering). A common scenario is to plot a one-dimensional array together with the current index position. This is done in three steps:

1. Display the array and the index, using ‘`Display`’.
2. Cluster both displays: select them and choose ‘`Undisp Cluster ()`’.
3. Plot the cluster by pressing ‘`Plot`’.

Scalars that are displayed together with arrays can be displayed either as vertical lines or horizontal lines. By default, scalars are plotted as horizontal lines. However, if a scalar is a valid index for an array that was previously plotted, it is shown as a vertical line. You can change this initial orientation by selecting the scalar display, followed by ‘`Rotate`’.

Next: Printing Plots, Previous: Scalars and Composites, Up: Plotting Values

#### 7.4.4 Plotting Display Histories

At each program stop, DDD records the values of all displayed variables, such that you can “undo” program execution (see Undoing Program Execution). These display histories can be plotted, too. The menu item ‘`Plot Plot history of ()`’ creates a plot that shows all previously recorded values of the selected display.

Next: Entering Plotting Commands, Previous: Plotting Histories, Up: Plotting Values

#### 7.4.5 Printing Plots

If you want to print the plot, select ‘`File Print Plot`’. This pops up the DDD printing dialog, set up for printing plots. Just as when printing graphs, you have the choice between printing to a printer or a file and setting up appropriate options.

The actual printing is also performed by Gnuplot, using the appropriate driver. Please note the following caveats related to printing:

- Creating ‘`FIG`’ files requires an appropriate driver built into Gnuplot. Your Gnuplot program may not contain such a driver. In this case, you will have to recompile Gnuplot, including the line ‘`#define FIG`’ in the Gnuplot ‘`term.h`’ file.
- The ‘`Portrait`’ option generates an EPS file useful for inclusion in other documents. The ‘`Landscape`’ option makes DDD print the plot in the size specified in the ‘`Paper Size`’ option; this is useful for printing on a printer. In ‘`Portrait`’ mode, the ‘`Paper Size`’ option is ignored.
- The Gnuplot device drivers for PostScript and X11 each have their own set of colors, such that the printed colors may differ from the displayed colors.
- The ‘`Selected Only`’ option is set by default, such that only the currently selected plot is printed. (If you select multiple plots to be printed, the respective outputs will all be concatenated, which may not be what you desire.)

Next: Exporting Plot Data, Previous: Printing Plots, Up: Plotting Values

#### 7.4.6 Entering Plotting Commands

Via ‘`File Command`’, you can enter Gnuplot commands directly. Each command entered at the ‘`gnuplot>`’ prompt is passed to Gnuplot, followed by a Gnuplot ‘`replot`’ command to update the view. This is useful for advanced Gnuplot tasks.

Here's a simple example. The Gnuplot command

         set xrange [xmin:xmax]

sets the horizontal range that will be displayed to xmin...xmax. To plot only the elements 10 to 20, enter:

         gnuplot> set xrange [10:20]
         gnuplot> _

After each command entered, DDD adds a `replot` command, such that the plot is updated automatically.

Here's a more complex example. The following sequence of Gnuplot commands saves the plot in TeX format:

         gnuplot> set output "plot.tex" # Set the output filename
         gnuplot> set term latex        # Set the output format
         gnuplot> set term x11          # Show original picture again
         gnuplot> _

Due to the implicit `replot` command, the output is automatically written to ‘`plot.tex`’ after the `set term latex` command.

The dialog keeps track of the commands entered; use the arrow keys to restore previous commands. Gnuplot error messages (if any) are also shown in the history area.

The interaction between DDD and Gnuplot is logged in the file `~/.ddd/log` (see Logging). The DDD `--trace` option logs this interaction on standard output.

Next: Animating Plots, Previous: Entering Plotting Commands, Up: Plotting Values

#### 7.4.7 Exporting Plot Data

If you want some external program to process the plot data (a stand-alone Gnuplot program or the `xmgr` program, for instance), you can save the plot data in a file, using ‘`File Save Data As`’. This pops up a dialog that lets you choose a data file to save the plotted data in.

The generated file starts with a few comment lines. The actual data follows in X/Y or X/Y/Z format. It is the same file as processed by Gnuplot.

Next: Customizing Plots, Previous: Exporting Plot Data, Up: Plotting Values

#### 7.4.8 Animating Plots

If you want to see how your data evolves in time, you can set a breakpoint whose command sequence ends in a `cont` command (see Breakpoint Commands. Each time this “continue” breakpoint is reached, the program stops and DDD updates the displayed values, including the plots. Then, DDD executes the breakpoint command sequence, resuming execution.

This way, you can set a “continue” breakpoint at some decisive point within an array-processing algorithm and have DDD display the progress graphically. When your program has stopped for good, you can use ‘`Undo`’ and ‘`Redo`’ to redisplay and examine previous program states. See Undoing Program Execution, for details.

Previous: Animating Plots, Up: Plotting Values

#### 7.4.9 Customizing Plots

You can customize the Gnuplot program to invoke, as well as a number of basic settings.

Next: Gnuplot Settings, Up: Customizing Plots

##### 7.4.9.1 Gnuplot Invocation

Using ‘`Edit Preferences Helpers Plot`’, you can choose the Gnuplot program to invoke. This is tied to the following resource:

— Resource: plotCommand (class PlotCommand)

> The name of a Gnuplot executable. Default is ‘`gnuplot`’, followed by some options to set up colors and the initial geometry.

Using ‘`Edit Preferences Helpers Plot Window`’, you can choose whether to use the Gnuplot plot window (‘`External`’) or to use the plot window supplied by DDD (‘`builtin`’). This is tied to the following resource:

— Resource: plotTermType (class PlotTermType)

> The Gnuplot terminal type. Can have one of two values:

> - If this is ‘`x11`’, DDD “swallows” the external Gnuplot output window into its own user interface. Some window managers, notably `mwm`, have trouble with swallowing techniques.
> - Setting this resource to ‘`xlib`’ (default) makes DDD provide a builtin plot window instead. In this mode, plots work well with any window manager, but are less customizable (Gnuplot resources are not understood).

You can further control interaction with the external plot window:

— Resource: plotWindowClass (class PlotWindowClass)

> The class of the Gnuplot output window. When invoking Gnuplot, DDD waits for a window with this class and incorporates it into its own user interface (unless ‘`plotTermType`’ is ‘`xlib`’; see above). Default is ‘`Gnuplot`’.

— Resource: plotWindowDelay (class WindowDelay)

> The time (in ms) to wait for the creation of the Gnuplot window. Before this delay, DDD looks at each newly created window to see whether this is the plot window to swallow. This is cheap, but unfortunately, some window managers do not pass the creation event to DDD. If this delay has passed, and DDD has not found the plot window, DDD searches all existing windows, which is pretty expensive. Default time is `2000`.

Previous: Gnuplot Invocation, Up: Customizing Plots

##### 7.4.9.2 Gnuplot Settings

To change Gnuplot settings, use these resources:

— Resource: plotInitCommands (class PlotInitCommands)

> The initial Gnuplot commands issued by DDD. Default is:

>               set parametric
>               set urange [0:1]
>               set vrange [0:1]
>               set trange [0:1]

> The ‘`parametric`’ setting is required to make Gnuplot understand the data files as generated DDD. The range commands are used to plot scalars.

See the Gnuplot documentation for additional commands.

— Resource: plot2dSettings (class PlotSettings)

> Additional initial settings for 2-D plots. Default is ‘`set noborder`’. Feel free to customize these settings as desired.

— Resource: plot3dSettings (class PlotSettings)

> Additional initial settings for 3-D plots. Default is ‘`set border`’. Feel free to customize these settings as desired.

Previous: Plotting Values, Up: Examining Data

### 7.5 Examining Memory

Using GDB or DBX, you can examine memory in any of several formats, independently of your program's data types. The item ‘`Data Memory`’ pops up a panel where you can choose the format to be shown.

In the panel, you can enter

- a repeat count, a decimal integer that specifies how much memory (counting by units) to display
- a display format—one of
  ‘`octal`’
    Print as integer in octal
  ‘`hex`’
    Regard the bits of the value as an integer, and print the integer in hexadecimal.
  ‘`decimal`’
    Print as integer in signed decimal.
  ‘`unsigned`’
    Print as integer in unsigned decimal.
  ‘`binary`’
    Print as integer in binary.
  ‘`float`’
    Regard the bits of the value as a floating point number and print using typical floating point syntax.
  ‘`address`’
    Print as an address, both absolute in hexadecimal and as an offset from the nearest preceding symbol.
  ‘`instruction`’
    Print as machine instructions. The unit size is ignored for this display format.
  ‘`char`’
    Regard as an integer and print it as a character constant.
  ‘`string`’
    Print as null-terminated string. The unit size is ignored for this display format.
- a unit size—one of
  ‘`bytes`’
    Bytes.
  ‘`halfwords`’
    Halfwords (two bytes).
  ‘`words`’
    Words (four bytes).
  ‘`giants`’
    Giant words (eight bytes).
- an address—the starting display address. The expression need not have a pointer value (though it may); it is always interpreted as an integer address of a byte of memory.

There are two ways to examine the values:

- You can dump the memory in the debugger console (using ‘`Print`’). If you repeat the resulting ‘`x`’ command by pressing <Return> in the debugger console (see Command History), the following area of memory is shown.
- You can also display the memory dump in the data window (using ‘`Display`’). If you choose to display the values, the values will be updated automatically each time the program stop.

Next: Changing the Program, Previous: Examining Data, Up: Top

## 8 Machine-Level Debugging

Sometimes, it is desirable to examine a program not only at the source level, but also at the machine level. DDD provides special machine code and register windows for this task.

Next: Machine Code Execution, Up: Machine-Level Debugging

### 8.1 Examining Machine Code

To enable machine-level support, select ‘`Source Display Machine Code`’. With machine code enabled, an additional machine code window shows up, displaying the machine code of the current function.30 By moving the sash at the right of the separating line between source and machine code, you can resize the source and machine code windows.

The machine code window works very much like the source window. You can set, clear, and change breakpoints by selecting the address and pressing a ‘`Break`’ or ‘`Clear`’ button; the usual popup menus are also available. Breakpoints and the current execution position are displayed simultaneously in both source and machine code.

The ‘`Lookup`’ button can be used to look up the machine code for a specific function—or the function for a specific address. Just click on the location in one window and press ‘`Lookup`’ to see the corresponding code in the other window.

If source code is not available, only the machine code window is updated.

You can customize various aspects of the disassembling window. See Customizing Machine Code, for details.

Next: Registers, Previous: Machine Code, Up: Machine-Level Debugging

### 8.2 Machine Code Execution

All execution facilities available in the source code window are available in the machine code window as well. Two special facilities are convenient for machine-level debugging:

To execute just one machine instruction, click on the ‘`Stepi`’ button or select ‘`Program Step Instruction`’.

To continue to the next instruction in the current function, click on the ‘`Nexti`’ button select ‘`Program Next Instruction`’.. This is similar to ‘`Stepi`’, but any subroutine calls are executed without stopping.

Using GDB, it is often useful to do

         graph display /i $pc

when stepping by machine instructions. This makes DDD automatically display the next instruction to be executed, each time your program stops.

Next: Customizing Machine Code, Previous: Machine Code Execution, Up: Machine-Level Debugging

### 8.3 Examining Registers

DDD provides a register window showing the machine register values after each program stop. To enable the register window, select ‘`Status Registers`’.31

By selecting one of the registers, its name is copied to the argument field. You can use it as value for ‘`Display`’, for instance, to have its value displayed in the data window.

Previous: Registers, Up: Machine-Level Debugging

### 8.4 Customizing Machine Code

Enabling machine code via ‘`Source Display Machine Code`’ (see Machine Code) toggles the following resource:

— Resource: disassemble (class Disassemble)

> If this is ‘`on`’, the source code is automatically disassembled. The default is ‘`off`’. See Options, for the `--disassemble` and `--no-disassemble` options.

You can keep disassembled code in memory, using ‘`Edit Preferences Source Cache Machine Code`’:

— Resource: cacheMachineCode (class CacheMachineCode)

> Whether to cache disassembled machine code (‘`on`’, default) or not (‘`off`’). Caching machine code requires more memory, but makes DDD run faster.

You can control the indentation of machine code, using ‘`Edit Preferences Source Machine Code Indentation`’:

— Resource: indentCode (class Indent)

> The number of columns to indent the machine code, such that there is enough place to display breakpoint locations. Default: `4`.

The ‘`maxDisassemble`’ resource controls how much is to be disassembled. If ‘`maxDisassemble`’ is set to 256 (default) and the current function is larger than 256 bytes, DDD only disassembles the first 256 bytes below the current location. You can set the ‘`maxDisassemble`’ resource to a larger value if you prefer to have a larger machine code view.

— Resource: maxDisassemble (class MaxDisassemble)

> Maximum number of bytes to disassemble (default: `256`). If this is zero, the entire current function is disassembled.

Next: Commands, Previous: Machine-Level Debugging, Up: Top

## 9 Changing the Program

DDD offers some basic facilities to edit and recompile the source code, as well as patching executables and core files.

Next: Recompiling, Up: Changing the Program

### 9.1 Editing Source Code

In DDD itself, you cannot change the source file currently displayed. Instead, DDD allows you to invoke a text editor. To invoke a text editor for the current source file, select the ‘`Edit`’ button or ‘`Source Edit Source`’.

By default, DDD tries a number of common editors. You can customize DDD to use your favorite editor; See Customizing Editing, for details.

After the editor has exited, the source code shown is automatically updated.

If you have DDD and an editor running in parallel, you can also update the source code manually via ‘`Source Reload Source`’. This reloads the source code shown from the source file. Since DDD automatically reloads the source code if the debugged program has been recompiled, this should seldom be necessary.

Next: In-Place Editing, Up: Editing Source Code

#### 9.1.1 Customizing Editing

You can customize the editor to be used via ‘`Edit Preferences Helpers Edit Sources`’. This is tied to the following resource:

— Resource: editCommand (class EditCommand)

> A command string to invoke an editor on the specific file. ‘`@LINE@`’ is replaced by the current line number, ‘`@FILE@`’ by the file name. The default is to invoke `$XEDITOR` first, then `$EDITOR`, then `vi`:

>               Ddd*editCommand: \
>               ${XEDITOR-false} +@LINE@ @FILE@ || \
>               xterm -e ${EDITOR-vi} +@LINE@ @FILE@

This `~/.ddd/init` setting invokes an editing session for an XEmacs editor running `gnuserv`:

         Ddd*editCommand: gnuclient +@LINE@ @FILE@

This `~/.ddd/init` setting invokes an editing session for an Emacs editor running `emacsserver`:

         Ddd*editCommand: emacsclient +@LINE@ @FILE@

Previous: Customizing Editing, Up: Editing Source Code

#### 9.1.2 In-Place Editing

This resource is experimental:

— Resource: sourceEditing (class SourceEditing)

> If this is ‘`on`’, the displayed source code becomes editable. This is an experimental feature; Default is ‘`off`’.

Next: Patching, Previous: Editing Source Code, Up: Changing the Program

### 9.2 Recompiling

To recompile the source code using `make`, you can select ‘`File Make`’. This pops up a dialog where you can enter a Make Target—typically the name of the executable. Clicking on the ‘`Make`’ button invokes the `make` program with the given target.

The ‘`Make`’ button on the command tool re-invokes `make` with the most recently given arguments.

Previous: Recompiling, Up: Changing the Program

### 9.3 Patching

Using GDB, you can open your program's executable code (and the core file) for both reading and writing. This allows alterations to machine code, such that you can intentionally patch your program's binary. For example, you might want to turn on internal debugging flags, or even to make emergency repairs.

Note that depending on your operating system, special preparation steps, such as setting permissions, may be needed before you can change executable files.

To patch the binary, enable ‘`Edit GDB Settings Writing into executable and core files`’. This makes GDB open executable and core files for both reading and writing. If you have already loaded a file, you must load it again (using ‘`Edit Open File`’ or ‘`Edit Open Core`’), for your new setting to take effect.

Be sure to turn off ‘`Writing into executable and core files`’ as soon as possible, to prevent accidental alterations to machine code.

Next: Application Defaults, Previous: Changing the Program, Up: Top

## 10 The Command-Line Interface

All the buttons you click within DDD get eventually translated into some debugger command, shown in the debugger console. You can also type in and edit these commands directly.

Next: TTY mode, Up: Commands

### 10.1 Entering Commands

In the debugger console, you can interact with the command interface of the inferior debugger. Enter commands at the debugger prompt—that is, ‘`(gdb)`’ for GDB, ‘`bashdb<>`’ for Bash, ‘`(dbx)`’ for DBX, ‘`>`’ ‘`thread[depth]`’ for JDB, ‘`(ladebug)`’ for Ladebug, ‘`mdb<>`’ for the GNU Make debugger, ‘`DB<>`’ for Perl, ‘`(Pydb)`’ for `pydb`, or ‘`>`’ for XDB. You can use arbitrary debugger commands; use the <Return> key to enter them.

Next: Command History, Up: Entering Commands

#### 10.1.1 Command Completion

When using GDB or Perl, you can use the <TAB> key for completing commands and arguments. This works in the debugger console as well as in all other text windows.

GDB can fill in the rest of a word in a command for you, if there is only one possibility; it can also show you what the valid possibilities are for the next word in a command, at any time. This works for GDB commands, GDB subcommands, and the names of symbols in your program.

Press the <TAB> key whenever you want GDB to fill out the rest of a word. If there is only one possibility, GDB fills in the word, and waits for you to finish the command (or press <RET> to enter it). For example, if you type

         (gdb) info bre_<TAB>

GDB fills in the rest of the word ‘`breakpoints`’, since that is the only `info` subcommand beginning with ‘`bre`’:

         (gdb) info breakpoints

You can either press <RET> at this point, to run the `info breakpoints` command, or backspace and enter something else, if ‘`breakpoints`’ does not look like the command you expected. (If you were sure you wanted `info breakpoints` in the first place, you might as well just type <RET> immediately after ‘`info bre`’, to exploit command abbreviations rather than command completion).

If there is more than one possibility for the next word when you press <TAB>, DDD sounds a bell. You can either supply more characters and try again, or just press <TAB> a second time; GDB displays all the possible completions for that word. For example, you might want to set a breakpoint on a subroutine whose name begins with ‘`make_`’, but when you type `b make_<TAB>`, DDD just sounds the bell. Typing <TAB> again displays all the function names in your program that begin with those characters. If you type <TAB> again, you cycle through the list of completions, for example:

         (gdb) b make_ <TAB>

    DDD sounds bell; press <TAB> again, to see:

         make_a_section_from_file     make_environ
         make_abs_section             make_function_type
         make_blockvector             make_pointer_type
         make_cleanup                 make_reference_type
         make_command                 make_symbol_completion_list
         (gdb) b make_ <TAB>

    DDD presents one expansion after the other:

         (gdb) b make_a_section_from_file <TAB>
         (gdb) b make_abs_section <TAB>
         (gdb) b make_blockvector <TAB>

After displaying the available possibilities, GDB copies your partial input (‘`b make_`’ in the example) so you can finish the command—by pressing <TAB> again, or by entering the remainder manually.

Sometimes the string you need, while logically a “word”, may contain parentheses or other characters that GDB normally excludes from its notion of a word. To permit word completion to work in this situation, you may enclose words in `'` (single quote marks) in GDB commands.

The most likely situation where you might need this is in typing the name of a C++ function. This is because C++ allows function overloading (multiple definitions of the same function, distinguished by argument type). For example, when you want to set a breakpoint you may need to distinguish whether you mean the version of `name` that takes an `int` parameter, `name(int)`, or the version that takes a `float` parameter, `name(float)`. To use the word-completion facilities in this situation, type a single quote `'` at the beginning of the function name. This alerts GDB that it may need to consider more information than usual when you press <TAB> to request word completion:

         (gdb) b 'bubble(_<TAB>
         bubble(double,double)    bubble(int,int)
         (gdb) b 'bubble(_

In some cases, DDD can tell that completing a name requires using quotes. When this happens, DDD inserts the quote for you (while completing as much as it can) if you do not type the quote in the first place:

         (gdb) b bub_<TAB>

    DDD alters your input line to the following, and rings a bell:

         (gdb) b 'bubble(_

In general, DDD can tell that a quote is needed (and inserts it) if you have not yet started typing the argument list when you ask for completion on an overloaded symbol.

If you prefer to use the <TAB> key for switching between items, unset ‘`Edit Preferences General TAB Key completes in All Windows`’. This is useful if you have pointer-driven keyboard focus (see below) and no special usage for the <TAB> key. If the option is set, the <TAB> key completes in the debugger console only.

This option is tied to the following resource:

— Resource: globalTabCompletion (class GlobalTabCompletion)

> If this is ‘`on`’ (default), the <TAB> key completes arguments in all windows. If this is ‘`off`’, the <TAB> key completes arguments in the debugger console only.

Next: Typing in the Source Window, Previous: Command Completion, Up: Entering Commands

#### 10.1.2 Command History

You can repeat previous and next commands by pressing the <Up> and <Down> arrow keys, respectively. This presents you previous and later commands on the command line; use <Return> to apply the current command.

If you enter an empty line (just use <Return> at the debugger prompt), the last command is repeated as well.

‘`Commands Command History`’ shows the command history.

You can search for previous commands by pressing <Ctrl+B>. This invokes incremental search mode, where you can enter a string to be searched in previous commands. Press <Ctrl+B> again to repeat the search, or <Ctrl+F> to search in the reverse direction. To return to normal mode, press <ESC>, or use any cursor command.

The command history is automatically saved when exiting DDD. You can turn off this feature by setting the following resource to ‘`off`’:

— Resource: saveHistoryOnExit (class SaveOnExit)

> If ‘`on`’ (default), the command history is automatically saved when DDD exits.

Previous: Command History, Up: Entering Commands

#### 10.1.3 Typing in the Source Window

As a special convenience, anything you type into the source window is automatically forwarded to the debugger console. Thus, you don't have to change the keyboard focus explicitly in order to enter commands.

You can change this behaviour using the following resource:

— Resource: consoleHasFocus (class ConsoleHasFocus)

> If ‘`on`’ (default), all keyboard events in the source window are automatically forwarded to the debugger console. If ‘`off`’, keyboard events are not forwarded. If ‘`auto`’, keyboard events forwarded only if the debugger console is open.

Next: Integrating <acronym>DDD</acronym>, Previous: Entering Commands, Up: Commands

### 10.2 Entering Commands at the TTY

Rather than entering commands at the debugger console, you may prefer to enter commands at the terminal window DDD was invoked from.

When DDD is invoked using the `--tty` option, it enables its TTY interface, taking additional debugger commands from standard input and forwarding debugger output to standard output, just as if the inferior debugger had been invoked directly. All remaining DDD functionality stays unchanged.

By default, the debugger console remains closed if DDD is invoked using the `--tty` option. Use ‘`View Debugger Console`’ to open it.

DDD can be configured to use the ‘`readline`’ library for reading in commands from standard input. This GNU library provides consistent behavior for programs which provide a command line interface to the user. Advantages are GNU Emacs-style or vi-style inline editing of commands, `csh`-like history substitution, and a storage and recall of command history across debugging sessions. See Command Line Editing, for details on command-line editing via the TTY interface.

Next: Defining Buttons, Previous: TTY mode, Up: Commands

### 10.3 Integrating DDD

You can run DDD as an inferior debugger in other debugger front-ends, combining their special abilities with those of DDD.

To have DDD run as an inferior debugger in other front-ends, the general idea is to set up your debugger front-end such that ‘`ddd --tty`’ is invoked instead of the inferior debugger. When DDD is invoked using the `--tty` option, it enables its TTY interface, taking additional debugger commands from standard input and forwarding debugger output to standard output, just as if the inferior debugger had been invoked directly. All remaining DDD functionality stays unchanged.

In case your debugger front-end uses the GDB `-fullname` option to have GDB report source code positions, the `--tty` option is not required. DDD recognizes the `-fullname` option, finds that it has been invoked from a debugger front-end and automatically enables the TTY interface.

If DDD is invoked with the `-fullname` option, the debugger console and the source window are initially disabled, as their facilities are supposed to be provided by the integrating front-end. In case of need, you can use the ‘`View`’ menu to re-enable these windows.

#### 10.3.1 Using DDD with Emacs

To integrate DDD with Emacs, use `M-x gdb` or `M-x dbx` in Emacs to start a debugging session. At the prompt, enter `ddd --tty` (followed by `--dbx` or `--gdb`, if required), and the name of the program to be debugged. Proceed as usual.

#### 10.3.2 Using DDD with XEmacs

To integrate DDD with XEmacs, set the variable `gdb-command-name` to ‘`"ddd"`’, by inserting the following line in your `~/.emacs` file:

         (setq gdb-command-name "ddd")

You can also evaluate this expression by pressing <ESC> <:> and entering it directly (<ESC> <ESC> for XEmacs 19.13 and earlier).

To start a DDD debugging session in XEmacs, use ‘`M-x gdb`’ or ‘`M-x gdbsrc`’. Proceed as usual.

#### 10.3.3 Using DDD with XXGDB

To integrate DDD with XXGDB, invoke `xxgdb` as

         xxgdb -db_name ddd -db_prompt '(gdb) '

Next: Defining Commands, Previous: Integrating <acronym>DDD</acronym>, Up: Commands

### 10.4 Defining Buttons

To facilitate interaction, you can add own command buttons to DDD. These buttons can be added below the debugger console (‘`Console Buttons`’), the source window (‘`Source Buttons`’), or the data window (‘`Data Buttons`’).

To define individual buttons, use the Button Editor, invoked via ‘`Commands Edit Buttons`’. The button editor displays a text, where each line contains the command for exactly one button. Clicking on ‘`OK`’ creates the appropriate buttons from the text. If the text is empty (the default), no button is created.

As a simple example, assume you want to create a ‘`print i`’ button. Invoke ‘`Commands Edit Buttons`’ and enter a line saying ‘`print i`’ in the button editor. Then click on ‘`OK`’. A button named ‘`Print i`’ will now appear below the debugger console—try it! To remove the button, reopen the button editor, clear the ‘`print i`’ line and press ‘`OK`’ again.

If a button command contains ‘`()`’, the string ‘`()`’ will automatically be replaced by the contents of the argument field. For instance, a button named ‘`return ()`’ will execute the GDB ‘`return`’ command with the current content of the argument field as argument.

By default, DDD disables buttons whose commands are not supported by the inferior debugger. To enable such buttons, unset the ‘`Enable supported buttons only`’ toggle in the button editor.

DDD also allows you to specify control sequences and special labels for user-defined buttons. See Customizing Buttons, for details.

Up: Defining Buttons

#### 10.4.1 Customizing Buttons

DDD allows defining additional command buttons; See Defining Buttons, for doing this interactively. This section describes the resources that control user-defined buttons.

— Resource: consoleButtons (class Buttons)

> A newline-separated list of buttons to be added under the debugger console. Each button issues the command given by its name.

> The following characters have special meanings:

> - Commands ending with `...` insert their name, followed by a space, in the debugger console.
> - Commands ending with a control character (that is, ‘`^`’ followed by a letter or ‘`?`’) insert the given control character.
> - The string ‘`()`’ is replaced by the current contents of the argument field ‘`()`’.
> - The string specified in the ‘`labelDelimiter`’ resource (usually ‘`//`’) separates the command name from the button label. If no button label is specified, the capitalized command will be used as button label.

> The following button names are reserved:

> ‘`Apply`’
>   Send the given command to the debugger.
> ‘`Back`’
>   Lookup previously selected source position.
> ‘`Clear`’
>   Clear current command
> ‘`Complete`’
>   Complete current command.
> ‘`Edit`’
>   Edit current source file.
> ‘`Forward`’
>   Lookup next selected source position.
> ‘`Make`’
>   Invoke the ‘`make`’ program, using the most recently given arguments.
> ‘`Next`’
>   Show next command
> ‘`No`’
>   Answer current debugger prompt with ‘`no`’. This button is visible only if the debugger asks a yes/no question.
> ‘`Prev`’
>   Show previous command
> ‘`Reload`’
>   Reload source file.
> ‘`Yes`’
>   Answer current debugger prompt with ‘`yes`’. This button is visible only if the debugger asks a yes/no question.

> The default resource value is empty—no console buttons are created.

> Here are some examples to insert into your `~/.ddd/init` file. These are the settings of DDD 1.x:

>               Ddd*consoleButtons: Yes\nNo\nbreak^C

> This setting creates some more buttons:

>                 Ddd*consoleButtons: \
>                 Yes\nNo\nrun\nClear\nPrev\nNext\nApply\nbreak^C

> See also the ‘`dataButtons`’, ‘`sourceButtons`’ and ‘`toolButtons`’ resources.

— Resource: dataButtons (class Buttons)

> A newline-separated list of buttons to be added under the data display. Each button issues the command given by its name. See the ‘`consoleButtons`’ resource, above, for details on button syntax.

> The default resource value is empty—no source buttons are created.

— Resource: sourceButtons (class Buttons)

> A newline-separated list of buttons to be added under the debugger console. Each button issues the command given by its name. See the ‘`consoleButtons`’ resource, above, for details on button syntax.

> The default resource value is empty—no source buttons are created.

> Here are some example to insert into your `~/.ddd/init` file. These are the settings of DDD 1.x:

>               Ddd*sourceButtons: \
>                 run\nstep\nnext\nstepi\nnexti\ncont\n\
>                 finish\nkill\nup\ndown\n\
>                 Back\nForward\nEdit\ninterrupt^C

> This setting creates some buttons which are not found on the command tool:

>                 Ddd*sourceButtons: \
>                 print *()\ngraph display *()\nprint /x ()\n\
>                 whatis ()\nptype ()\nwatch ()\nuntil\nshell

> An even more professional setting uses customized button labels.

>                 Ddd*sourceButtons: \
>                 print *(()) // Print *()\n\
>                 graph display *(()) // Display *()\n\
>                 print /x ()\n\
>                 whatis () // What is ()\n\
>                 ptype ()\n\
>                 watch ()\n\
>                 until\n\
>                 shell

> See also the ‘`consoleButtons`’ and ‘`dataButtons`’ resources, above, and the ‘`toolButtons`’ resource, below.

— Resource: toolButtons (class Buttons)

> A newline-separated list of buttons to be included in the command tool or the command tool bar (see Disabling the Command Tool). Each button issues the command given by its name. See Defining Buttons, for details on button syntax.

> The default resource value is

>               Ddd*toolButtons: \
>               run\nbreak^C\nstep\nstepi\nnext\nnexti\n\
>               until\nfinish\ncont\n\kill\n\
>               up\ndown\nBack\nForward\nEdit\nMake

> For each button, its location in the command tool must be specified using ‘`XmForm`’ constraint resources. See the ‘`Ddd`’ application defaults file for instructions.

> If the ‘`toolButtons`’ resource value is empty, the command tool is not created.

The following resources set up button details:

— Resource: labelDelimiter (class LabelDelimiter)

> The string used to separate labels from commands and shortcuts. Default is ‘`//`’.

— Resource: verifyButtons (class VerifyButtons)

> If ‘`on`’ (default), verify for each button whether its command is actually supported by the inferior debugger. If the command is unknown, the button is disabled. If this resource is ‘`off`’, no checking is done: all commands are accepted “as is”.

Previous: Defining Buttons, Up: Commands

### 10.5 Defining Commands

Aside from breakpoint commands (see Breakpoint Commands), DDD also allows you to define user-defined commands. A user-defined command is a sequence of commands to which you assign a new name as a command. This new command can be entered at the debugger prompt or invoked via a button.

Next: GDB Argument Commands, Up: Defining Commands

#### 10.5.1 Defining Simple Commands using GDB

Aside from breakpoint commands (see ‘`Breakpoint commands`’, above), DDD also allows you to store sequences of commands as a user-defined GDB command. A user-defined command is a sequence of GDB commands to which you assign a new name as a command. Using DDD, this is done via the Command Editor, invoked via ‘`Commands Define Command`’.

A GDB command is created in five steps:

1. Enter the name of the command in the ‘`Command`’ field. Use the drop-down list on the right to select from already defined commands.
2. Click on ‘`Record`’ to begin the recording of the command sequence.
3. Now interact with DDD. While recording, DDD does not execute commands, but simply records them to be executed when the breakpoint is hit. The recorded debugger commands are shown in the debugger console.
4. To stop the recording, click on ‘`End`’ or enter ‘`end`’ at the GDB prompt. To cancel the recording, click on ‘`Interrupt`’ or press <ESC>.
5. Click on ‘`Edit >>`’ to edit the recorded commands. When done with editing, click on ‘`Edit <<`’ to close the commands editor.

After the command is defined, you can enter it at the GDB prompt. You may also click on ‘`Execute`’ to test the given user-defined command.

For convenience, you can assign a button to the defined command. Enabling one of the ‘`Button`’ locations will add a button with the given command to the specified location. If you want to edit the button, select ‘`Commands Edit Buttons`’. See Defining Buttons, for a discussion.

When user-defined GDB commands are executed, the commands of the definition are not printed. An error in any command stops execution of the user-defined command.32

If used interactively, commands that would ask for confirmation proceed without asking when used inside a user-defined command. Many GDB commands that normally print messages to say what they are doing omit the messages when used in a user-defined command.

Command definitions are saved across DDD sessions.

Next: Commands with Other Debuggers, Previous: GDB Simple Commands, Up: Defining Commands

#### 10.5.2 Defining Argument Commands using GDB

If you want to pass arguments to user-defined commands, you can enable the ‘`()`’ toggle button in the Command Editor. Enabling ‘`()`’ has two effects:

- While recording commands, all references to the argument field are taken symbolically instead of literally. The argument field value is frozen to ‘`$arg0`’, which is how GDB denotes the argument of a user-defined command. When GDB executes the command, it will replace ‘`$arg0`’ by the current command argument.
- When assigning a button to the command, the command will be suffixed by the current contents of the argument field.

While defining a command, you can toggle the ‘`()`’ button as you wish to switch between using the argument field symbolically and literally.

As an example, let us define a command `contuntil` that will set a breakpoint in the given argument and continue execution.

1. Enter ‘`contuntil`’ in the ‘`Command`’ field.
2. Enable the ‘`()`’ toggle button.
3. Now click on ‘`Record`’ to start recording. Note that the contents of the argument field change to ‘`$arg0`’.
4. Click on ‘`Break at ()`’ to create a breakpoint. Note that the recorded breakpoint command refers to ‘`$arg0`’.
5. Click on ‘`Cont`’ to continue execution.
6. Click on ‘`End`’ to end recording. Note that the argument field is restored to its original value.
7. Finally, click on one of the ‘`Button`’ locations. This creates a ‘`Contuntil ()`’ button where ‘`()`’ will be replaced by the current contents of the argument field—and thus passed to the ‘`contuntil`’ command.
8. You can now either use the ‘`Contuntil ()`’ button or enter a ‘`contuntil`’ command at the GDB prompt. (If you plan to use the command frequently, you may wish to define a ‘`cu`’ command, which again calls ‘`contuntil`’ with its argument. This is a nice exercise.)

There is a little drawback with argument commands: a user-defined command in GDB has no means to access the argument list as a whole; only the first argument (up to whitespace) is processed. This may change in future GDB releases.

Previous: GDB Argument Commands, Up: Defining Commands

#### 10.5.3 Defining Commands using Other Debuggers

If your inferior debugger allows you to define own command sequences, you can also use these user-defined commands within DDD; just enter them at the debugger prompt.

However, you may encounter some problems:

- In contrast to the well-documented commands of the inferior debugger, DDD does not know what a user-defined command does. This may lead to inconsistencies between DDD and the inferior debugger. For instance, if your the user-defined command ‘`bp`’ sets a breakpoint, DDD may not display it immediately, because DDD does not know that ‘`bp`’ changes the breakpoint state.
- You cannot use DDD ‘`graph`’ commands within user-defined commands. This is only natural, because user-defined commands are interpreted by the inferior debugger, which does not know about DDD commands.

As a solution, DDD provides a simple facility called auto-commands. If DDD receives any output from the inferior debugger in the form ‘`prefix command`’, it will interpret command as if it had been entered at the debugger prompt. prefix is a user-defined string, for example ‘`ddd:` ’.

Suppose you want to define a command `gd` that serves as abbreviation for `graph display`. All the command `gd` has to do is to issue a string

         ddd: graph display argument

where argument is the argument given to `gd`. Using GDB, this can be achieved using the `echo` command. In your `~/.gdbinit` file, insert the lines

         define gd
           echo ddd: graph display $arg0\n
         end

To complete the setting, you must also set the ‘`autoCommandPrefix`’ resource to the ‘`ddd:` ’ prefix you gave in your command. In `~/.ddd/init`, write:

         Ddd*autoCommandPrefix: ddd:\

(Be sure to leave a space after the trailing backslash.)

Entering `gd foo` will now have the same effect as entering `graph display foo` at the debugger prompt.

Please note: In your commands, you should choose some other prefix than ‘`ddd:` ’. This is because auto-commands raise a security problem, since arbitrary commands can be executed. Just imagine some malicious program issuing a string like ‘`prefix shell rm -fr ~`’ when being debugged! As a consequence, be sure to choose your own prefix; it must be at least three characters long.

Next: Bugs, Previous: Commands, Up: Top

## Appendix A Application Defaults

Like any good X citizen, DDD comes with a large application-defaults file named `Ddd`. This appendix documents the actions and images referenced in `Ddd`, such that you can easily modify them.

Next: Images, Up: Application Defaults

### A.1 Actions

The following DDD actions may be used in translation tables.

Next: Data Display Actions, Up: Actions

#### A.1.1 General Actions

— Action: ddd-get-focus ()

> Assign focus to the element that just received input.

— Action: ddd-next-tab-group ()

> Assign focus to the next tab group.

— Action: ddd-prev-tab-group ()

> Assign focus to the previous tab group.

— Action: ddd-previous-tab-group ()

> Assign focus to the previous tab group.

Next: Debugger Console Actions, Previous: General Actions, Up: Actions

#### A.1.2 Data Display Actions

These actions are used in the DDD graph editor.

— Action: end ()

> End the action initiated by `select`. Bound to a button up event.

— Action: extend ()

> Extend the current selection. Bound to a button down event.

— Action: extend-or-move ()

> Extend the current selection. Bound to a button down event. If the pointer is dragged, move the selection.

— Action: follow ()

> Continue the action initiated by `select`. Bound to a pointer motion event.

— Action: graph-select ()

> Equivalent to `select`, but also updates the current argument.

— Action: graph-select-or-move ()

> Equivalent to `select-or-move`, but also updates the current argument.

— Action: graph-extend ()

> Equivalent to `extend`, but also updates the current argument.

— Action: graph-extend-or-move ()

> Equivalent to `extend-or-move`, but also updates the current argument.

— Action: graph-toggle ()

> Equivalent to `toggle`, but also updates the current argument.

— Action: graph-toggle-or-move ()

> Equivalent to `toggle-or-move`, but also updates the current argument.

— Action: graph-popup-menu ([`graph`|`node`|`shortcut`])

> Pops up a menu. `graph` pops up a menu with global graph operations, `node` pops up a menu with node operations, and `shortcut` pops up a menu with display shortcuts.

> If no argument is given, pops up a menu depending on the context: when pointing on a node with the <Shift> key pressed, behaves like `shortcut`; when pointing on a without the <Shift> key pressed, behaves like `node`; otherwise, behaves as if `graph` was given.

— Action: graph-dereference ()

> Dereference the selected display.

— Action: graph-detail ()

> Show or hide detail of the selected display.

— Action: graph-rotate ()

> Rotate the selected display.

— Action: graph-dependent ()

> Pop up a dialog to create a dependent display.

— Action: hide-edges ([`any`|`both`|`from`|`to`])

> Hide some edges. `any` means to process all edges where either source or target node are selected. `both` means to process all edges where both nodes are selected. `from` means to process all edges where at least the source node is selected. `to` means to process all edges where at least the target node is selected. Default is `any`.

— Action: layout ([`regular`|`compact`], [[`+`|`-`] degrees])

> Layout the graph. `regular` means to use the regular layout algorithm; `compact` uses an alternate layout algorithm, where successors are placed next to their parents. Default is `regular`. degrees indicates in which direction the graph should be layouted. Default is the current graph direction.

— Action: move-selected (x-offset, y-offset)

> Move all selected nodes in the direction given by x-offset and y-offset. x-offset and y-offset is either given as a numeric pixel value, or as ‘`+grid`’, or `-grid`, meaning the current grid size.

— Action: normalize ()

> Place all nodes on their positions and redraw the graph.

— Action: rotate ([[`+`|`-`]degrees])

> Rotate the graph around degrees degrees. degrees must be a multiple of 90. Default is `+90`.

— Action: select ()

> Select the node pointed at. Clear all other selections. Bound to a button down event.

— Action: select-all ()

> Select all nodes in the graph.

— Action: select-first ()

> Select the first node in the graph.

— Action: select-next ()

> Select the next node in the graph.

— Action: select-or-move ()

> Select the node pointed at. Clear all other selections. Bound to a button down event. If the pointer is dragged, move the selected node.

— Action: select-prev ()

> Select the previous node in the graph.

— Action: show-edges ([`any`|`both`|`from`|`to`])

> Show some edges. `any` means to process all edges where either source or target node are selected. `both` means to process all edges where both nodes are selected. `from` means to process all edges where at least the source node is selected. `to` means to process all edges where at least the target node is selected. Default is `any`.

— Action: snap-to-grid ()

> Place all nodes on the nearest grid position.

— Action: toggle ()

> Toggle the current selection—if the node pointed at is selected, it will be unselected, and vice versa. Bound to a button down event.

— Action: toggle-or-move ()

> Toggle the current selection—if the node pointed at is selected, it will be unselected, and vice versa. Bound to a button down event. If the pointer is dragged, move the selection.

— Action: unselect-all ()

> Clear the selection.

Next: Source Window Actions, Previous: Data Display Actions, Up: Actions

#### A.1.3 Debugger Console Actions

These actions are used in the debugger console and other text fields.

— Action: gdb-backward-character ()

> Move one character to the left. Bound to `Left`.

— Action: gdb-beginning-of-line ()

> Move cursor to the beginning of the current line, after the prompt. Bound to `HOME`.

— Action: gdb-control (control-character)

> Send the given control-character to the inferior debugger. control-character must be specified in the form ‘`^X`’, where X is an upper-case letter, or ‘`?`’.

— Action: gdb-command (command)

> Execute command in the debugger console. The following replacements are performed on command:

> - If command has the form ‘`name...`’, insert name, followed by a space, in the debugger console.
> - All occurrences of ‘`()`’ are replaced by the current contents of the argument field ‘`()`’.

— Action: gdb-complete-arg (command)

> Complete current argument as if command was prepended. Bound to <Ctrl+T>.

— Action: gdb-complete-command ()

> Complete current command line in the debugger console. Bound to <TAB>.

— Action: gdb-complete-tab (command)

> If global <TAB> completion is enabled, complete current argument as if command was prepended. Otherwise, proceed as if the <TAB> key was hit. Bound to <TAB>.

— Action: gdb-delete-or-control (control-character)

> Like `gdb-control`, but effective only if the cursor is at the end of a line. Otherwise, control-character is ignored and the character following the cursor is deleted. Bound to <Ctrl+D>.

— Action: gdb-end-of-line ()

> Move cursor to the end of the current line. Bound to `End`.

— Action: gdb-forward-character ()

> Move one character to the right. Bound to `Right`.

— Action: gdb-insert-graph-arg ()

> Insert the contents of the data display argument field ‘`()`’.

— Action: gdb-insert-source-arg ()

> Insert the contents of the source argument field ‘`()`’.

— Action: gdb-interrupt ()

> If DDD is in incremental search mode, exit it; otherwise call `gdb-control(^C)`.

— Action: gdb-isearch-prev ()

> Enter reverse incremental search mode. Bound to <Ctrl+B>.

— Action: gdb-isearch-next ()

> Enter incremental search mode. Bound to <Ctrl+F>.

— Action: gdb-isearch-exit ()

> Exit incremental search mode. Bound to <ESC>.

— Action: gdb-next-history ()

> Recall next command from history. Bound to `Down`.

— Action: gdb-prev-history ()

> Recall previous command from history. Bound to `Up`.

— Action: gdb-previous-history ()

> Recall previous command from history. Bound to `Up`.

— Action: gdb-process ([action [, args...]])

> Process the given event in the debugger console. Bound to key events in the source and data window. If this action is bound to the source window, and the source window is editable, perform action`(`args`...)` on the source window instead; if action is not given, perform ‘`self-insert()`’.

— Action: gdb-select-all ()

> If the ‘`selectAllBindings`’ resource is set to `Motif`, perform ‘`beginning-of-line`’. Otherwise, perform ‘`select-all`’. Bound to <Ctrl+A>.

— Action: gdb-set-line (value)

> Set the current line to value. Bound to <Ctrl+U>.

Previous: Debugger Console Actions, Up: Actions

#### A.1.4 Source Window Actions

These actions are used in the source and code windows.

— Action: source-delete-glyph ()

> Delete the breakpoint related to the glyph at cursor position.

— Action: source-double-click ([text-action [, line-action [, function-action]]])

> The double-click action in the source window.

> - If this action is taken on a breakpoint glyph, edit the breakpoint properties.
> - If this action is taken in the breakpoint area, invoke ‘`gdb-command(line-action)`’. If line-action is not given, it defaults to ‘`break ()`’.
> - If this action is taken in the source text, and the next character following the current selection is ‘`(`’, invoke ‘`gdb-command(function-action)`’. If function-action is not given, it defaults to ‘`list ()`’.
> - Otherwise, invoke ‘`gdb-command(text-action)`’. If text-action is not given, it defaults to ‘`graph display ()`’.

— Action: source-drag-glyph ()

> Initiate a drag on the glyph at cursor position.

— Action: source-drop-glyph ([action])

> Drop the dragged glyph at cursor position. action is either ‘`move`’, meaning to move the dragged glyph, or ‘`copy`’, meaning to copy the dragged glyph. If no action is given, ‘`move`’ is assumed.

— Action: source-end-select-word ()

> End selecting a word.

— Action: source-follow-glyph ()

> Continue a drag on the glyph at cursor position. Usually bound to some motion event.

— Action: source-popup-menu ()

> Pop up a menu, depending on the location.

— Action: source-set-arg ()

> Set the argument field to the current selection. Typically bound to some selection operation.

— Action: source-start-select-word ()

> Start selecting a word.

— Action: source-update-glyphs ()

> Update all visible glyphs. Usually invoked after a scrolling operation.

Previous: Actions, Up: Application Defaults

### A.2 Images

DDD installs a number of images that may be used as pixmap resources, simply by giving a symbolic name. For button images, three variants are installed as well:

- The suffix `-hi` indicates a highlighted variant (Button is entered).
- The suffix `-arm` indicates an armed variant (Button is pushed).
- The suffix `-xx` indicates a disabled (insensitive) variant.

— Image: break_at

> ‘`Break at ()`’ button.

— Image: clear_at

> ‘`Clear at ()`’ button.

— Image: ddd

> DDD icon.

— Image: delete

> ‘`Delete ()`’ button.

— Image: disable

> ‘`Disable`’ button.

— Image: dispref

> ‘`Display * ()`’ button.

— Image: display

> ‘`Display ()`’ button.

— Image: drag_arrow

> The execution pointer (being dragged).

— Image: drag_cond

> A conditional breakpoint (being dragged).

— Image: drag_stop

> A breakpoint (being dragged).

— Image: drag_temp

> A temporary breakpoint (being dragged).

— Image: enable

> ‘`Enable`’ button.

— Image: find_forward

> ‘`Find>> ()`’ button.

— Image: find_backward

> ‘`Find<< ()`’ button.

— Image: grey_arrow

> The execution pointer (not in lowest frame).

— Image: grey_cond

> A conditional breakpoint (disabled).

— Image: grey_stop

> A breakpoint (disabled).

— Image: grey_temp

> A temporary breakpoint (disabled).

— Image: hide

> ‘`Hide ()`’ button.

— Image: lookup

> ‘`Lookup ()`’ button.

— Image: maketemp

> ‘`Make Temporary`’ button.

— Image: new_break

> ‘`New Breakpoint`’ button.

— Image: new_display

> ‘`New Display`’ button.

— Image: new_watch

> ‘`New Watchpoint`’ button.

— Image: plain_arrow

> The execution pointer.

— Image: plain_cond

> A conditional breakpoint (enabled).

— Image: plain_stop

> A breakpoint (enabled).

— Image: plain_temp

> A temporary breakpoint (enabled).

— Image: print

> ‘`Print ()`’ button.

— Image: properties

> ‘`Properties`’ button.

— Image: rotate

> ‘`Rotate ()`’ button.

— Image: set

> ‘`Set ()`’ button.

— Image: show

> ‘`Show ()`’ button.

— Image: signal_arrow

> The execution pointer (stopped by signal).

— Image: undisplay

> ‘`Undisplay ()`’ button.

— Image: unwatch

> ‘`Unwatch ()`’ button.

— Image: watch

> ‘`Watch ()`’ button.

Next: Configuration Notes, Previous: Application Defaults, Up: Top

## Appendix B Bugs and How To Report Them

Sometimes you will encounter a bug in DDD. Although we cannot promise we can or will fix the bug, and we might not even agree that it is a bug, we want to hear about bugs you encounter in case we do want to fix them.

To make it possible for us to fix a bug, you must report it. In order to do so effectively, you must know when and how to do it.

Next: Is it a <acronym>DDD</acronym> Bug?, Up: Bugs

### B.1 Where to Send Bug Reports

Submit bug reports for DDD at http://savannah.gnu.org/bugs/?group=ddd, the DDD bug tracker. Incoming bug reports are automatically copied to the developers' mailing list bug-ddd@gnu.org.

Next: How to Report Bugs, Previous: Where to Send Bug Reports, Up: Bugs

### B.2 Is it a DDD Bug?

Before sending in a bug report, try to find out whether the problem cause really lies within DDD. A common cause of problems are incomplete or missing X or M*tif installations, for instance, or bugs in the X server or M*tif itself. Running DDD as

         $ ddd --check-configuration

checks for common problems and gives hints on how to repair them.

Another potential cause of problems is the inferior debugger; occasionally, they show bugs, too. To find out whether a bug was caused by the inferior debugger, run DDD as

         $ ddd --trace

This shows the interaction between DDD and the inferior debugger on standard error while DDD is running. (If `--trace` is not given, this interaction is logged in the file `~/.ddd/log`; see Logging) Compare the debugger output to the output of DDD and determine which one is wrong.

Next: Bug Reports, Previous: Is it a <acronym>DDD</acronym> Bug?, Up: Bugs

### B.3 How to Report Bugs

Here are some guidelines for bug reports:

- The fundamental principle of reporting bugs usefully is this: report all the facts. If you are not sure whether to state a fact or leave it out, state it!
- Keep in mind that the purpose of a bug report is to enable someone to fix the bug if it is not known. It is not very important what happens if the bug is already known. Therefore, always write your bug reports on the assumption that the bug is not known.
- Your bug report should be self-contained. Do not refer to information sent in previous mails; your previous mail may have been forwarded to somebody else.
- Please report each bug in a separate message. This makes it easier for us to track which bugs have been fixed and to forward your bugs reports to the appropriate maintainer.
- Please report bugs in English; this increases the chances of finding someone who can fix the bug. Do not assume one particular person will receive your bug report.

Next: Diagnostics, Previous: How to Report Bugs, Up: Bugs

### B.4 What to Include in a Bug Report

To enable us to fix a DDD bug, you must include the following information:

- Your DDD configuration. Invoke DDD as

                $ ddd --configuration

  to get the configuration information. If this does not work, please include at least the DDD version, the type of machine you are using, and its operating system name and version number.

- The debugger you are using and its version (e.g., ‘`gdb-4.17`’ or ‘`dbx as shipped with Solaris 2.6`’).
- The compiler you used to compile DDD and its version (e.g., ‘`gcc-2.8.1`’).
- A description of what behavior you observe that you believe is incorrect. For example, “DDD gets a fatal signal” or “DDD exits immediately after attempting to create the data window“.
- A log file showing the interaction between DDD and the inferior debugger. By default, this interaction is logged in the file `~/.ddd/log`. Include all trace output from the DDD invocation up to the first bug occurrence; insert own comments where necessary.
- If you wish to suggest changes to the DDD source, send us context diffs. If you even discuss something in the DDD source, refer to it by context, never by line number.

Be sure to include this information in every single bug report.

Previous: Bug Reports, Up: Bugs

### B.5 Getting Diagnostics

Next: Debugging <acronym>DDD</acronym>, Up: Diagnostics

#### B.5.1 Logging

If things go wrong, the first and most important information source is the DDD log file. This file, created in `~/.ddd/log` (`~` stands for your home directory), records the following information:

- Your DDD configuration (at the top)
- All programs invoked by DDD, shown as ‘`$ program args`...``’
- All DDD messages, shown as ‘`# message`’.
- All information sent from DDD to the inferior debugger, shown as `-> text`.
- All information sent from the inferior debugger standard output to DDD, shown as ‘`<- text`’.
- All information sent from the inferior debugger standard error to DDD, shown as ‘`<= text`’.33
- All information sent from DDD to Gnuplot, shown as ‘`>> text`’.
- All information sent from Gnuplot standard output to DDD, shown as ‘`<< text`’.
- All information sent from Gnuplot standard error to DDD, shown as ‘`<= text`’.
- If DDD crashes, a GDB backtrace of the DDD core dump is included at the end.

This information, all in one place, should give you (and anyone maintaining DDD) a first insight of what's going wrong.

Up: Logging

##### B.5.1.1 Disabling Logging

The log files created by DDD can become quite large, so you might want to turn off logging. There is no explicit DDD feature that allows you to do that. However, you can easily create a symbolic link from `~/.ddd/log` to ‘`/dev/null`’, such that logging information is lost. Enter the following commands at the shell prompt:

         $ cd
         $ rm .ddd/log
         $ ln -s /dev/null .ddd/log
         $ _

Be aware, though, that having logging turned off makes diagnostics much more difficult; in case of trouble, it may be hard to reproduce the error.

Next: Customizing Diagnostics, Previous: Logging, Up: Diagnostics

#### B.5.2 Debugging DDD

As long as DDD is compiled with `-g` (see Compiling for Debugging), you can invoke a debugger on DDD—even DDD itself, if you wish. From within DDD, a special ‘`Maintenance`’ menu is provided that invokes GDB on the running DDD process. See Maintenance Menu, for details.

The DDD distribution comes with a `.gdbinit` file that is suitable for debugging DDD. Among others, this defines a ‘`ddd`’ command that sets up an environment for debugging DDD and a ‘`string`’ command that lets you print the contents of DDD ‘`string`’ variables; just use ‘`print var`’ followed by ‘`string`’.

You can cause DDD to dump core at any time by sending it a `SIGUSR1` signal. DDD resumes execution while you can examine the core file with GDB.

When debugging DDD, it can be useful to make DDD not catch fatal errors. This can be achieved by setting the environment variable `DDD_NO_SIGNAL_HANDLERS` before invoking DDD.

Previous: Debugging <acronym>DDD</acronym>, Up: Diagnostics

#### B.5.3 Customizing Diagnostics

You can use these additional resources to obtain diagnostics about DDD. Most of them are tied to a particular invocation option.

— Resource: appDefaultsVersion (class Version)

> The version of the DDD app-defaults file. If this string does not match the version of the current DDD executable, DDD issues a warning.

— Resource: checkConfiguration (class CheckConfiguration)

> If ‘`on`’, check the DDD environment (in particular, the X configuration), report any possible problem causes and exit. See Options, for the `--check-configuration` option.

— Resource: dddinitVersion (class Version)

> The version of the DDD executable that last wrote the `~/.ddd/init` file. If this string does not match the version of the current DDD executable, DDD issues a warning.

— Resource: debugCoreDumps (class DebugCoreDumps)

> If ‘`on`’, DDD invokes a debugger on itself when receiving a fatal signal. See Maintenance Menu, for setting this resource.

— Resource: dumpCore (class DumpCore)

> If ‘`on`’ (default), DDD dumps core when receiving a fatal signal. See Maintenance Menu, for setting this resource.

— Resource: maintenance (class Maintenance)

> If ‘`on`’, enables the top-level ‘`Maintenance`’ menu (see Maintenance Menu) with additional options. See Options, for the `--maintenance` option.

— Resource: showConfiguration (class ShowConfiguration)

> If ‘`on`’, show the DDD configuration on standard output and exit. See Options, for the `--configuration` option.

— Resource: showFonts (class ShowFonts)

> If ‘`on`’, show the DDD font definitions on standard output and exit. See Options, for the `--fonts` option.

— Resource: showInvocation (class ShowInvocation)

> If ‘`on`’, show the DDD invocation options on standard output and exit. See Options, for the `--help` option.

— Resource: showLicense (class ShowLicense)

> If ‘`on`’, show the DDD license on standard output and exit. See Options, for the `--license` option.

— Resource: showManual (class ShowManual)

> If ‘`on`’, show this DDD manual page on standard output and exit. If the standard output is a terminal, the manual page is shown in a pager (`$PAGER`, `less` or `more`). See Options, for the `--manual` option.

— Resource: showNews (class ShowNews)

> If ‘`on`’, show the DDD news on standard output and exit. See Options, for the `--news` option.

— Resource: showVersion (class ShowVersion)

> If ‘`on`’, show the DDD version on standard output and exit. See Options, for the `--version` option.

— Resource: suppressWarnings (class SuppressWarnings)

> If ‘`on`’, X warnings are suppressed. This is sometimes useful for executables that were built on a machine with a different X or M*tif configuration. By default, this is ‘`off`’. See X Warnings, for details.

— Resource: trace (class Trace)

> If ‘`on`’, show the dialog between DDD and the inferior debugger on standard output. Default is ‘`off`’. See Options, for the `--trace` option.

Next: Dirty Tricks, Previous: Bugs, Up: Top

## Appendix C Configuration Notes

Next: Bash, Up: Configuration Notes

### C.1 Using DDD with GDB

Some GDB settings are essential for DDD to work correctly. These settings with their correct values are:

         set height 0
         set width 0
         set verbose off
         set annotate 1
         set prompt (gdb)

DDD sets these values automatically when invoking GDB; if these values are changed, there may be some malfunctions, especially in the data display.

When debugging at the machine level with GDB 4.12 and earlier as inferior debugger, use a ‘`display /x $pc`’ command to ensure the program counter value is updated correctly at each stop. You may also enter the command in `~/.gdbinit` or (better yet) upgrade to the most recent GDB version.

Next: WindRiver GDB, Up: GDB

#### C.1.1 Using DDD with WDB

HP's WildeBeest (WDB) is essentially a variant of GDB. To start DDD with WDB as inferior debugger, use

         ddd --wdb program

See GDB, for further configuration notes.

Previous: WDB, Up: GDB

#### C.1.2 Using DDD with WindRiver GDB (Tornado)

DDD now supports WindRiver's version of GDB.34 DDD can be integrated into the ‘`Launch`’ window by placing the `launch.tcl` script (see below) into the the directory `~/.wind`.

Currently, DDD only supports the PowerPC and has been only tested on a Solaris 2.6 host.

DDD launches the version of GDB that is either in the current path, or the one specified on the command line using the ‘`--debugger`’ command.

Normally, the Tornado environment is set up by sourcing a script file which, among other things, sets up the PATH variable.

It is suggested that a soft link for the version of GDB used for the target (i.e. `gdbppc`) be made in the same directory:

         bin>ls -l gdb*
         39 Mar  6 16:14 gdb -> /usr/wind/host/sun4-solaris2/bin/gdbppc*
         1619212 Mar 11  1997 gdbppc*
         bin>_

This way DDD will start the correct version of GDB automatically.

It is also suggested that you use DDD's execution window to facilitate parsing of GDB output. See Debugger Communication, for details.

Tornado reads the default TCL scripts first, then the ones in the users `.wind` directory. The following procedures can be cut and pasted into the user's `launch.tcl` file:

         # Launch.tcl - Launch application Tcl user customization file.
         #

         ######
         #
         # setupDDD - sets up DDD for use by the launcher
         #
         # This routine adds the DDD to the application bar
         #
         # SYNOPSIS:
         # setupDDD
         #
         # PARAMETERS: N/A
         #
         # RETURNS: N/A
         #
         # ERRORS: N/A
         #

         proc setupDDD {} {
             # Add to the default application bar
             objectCreate app ddd DDD {launchDDD}
         }

         ######
         #
         # launchDDD - launch the DDD debugger
         #
         # SYNOPSIS:
         # launchDDD
         #
         # PARAMETERS: N/A
         #
         # RETURNS: N/A
         #
         # ERRORS: N/A
         #

         proc launchDDD {} {

             global tgtsvr_selected
             global tgtsvr_cpuid

             if {$tgtsvr_selected == "" || $tgtsvr_cpuid == 0} {
                 noticePost error "Select an attached target first."
                 return
             }

             set startFileName /tmp/dddstartup.[pid]

             if [catch {open $startFileName w} file] {
                  # couldn't create a startup file.  Oh, well.
                  exec ddd --gdb &
             }
             else
             {
                  # write out a little /tmp file that attaches to the
                  # selected target server and then deletes itself.
                  puts $file "set wtx-tool-name ddd"
                  puts $file "target wtx $tgtsvr_selected"
                  puts $file "tcl exec rm $startFileName"
                  close $file
                  exec ddd --gdb --command=$startFileName &
             }
         }

         ######
         #
         # Launch.tcl - Initialization
         #
         # The user's resource file sourced from the initial Launch.tcl
         #

         # Add DDD to the laucher
           setupDDD

In order for DDD to automatically display the source of a previously loaded file, the entry point must be named either ‘`vxworks_main`’ or ‘`main_vxworks`’.

See GDB, for further configuration notes.

Next: DBX, Previous: GDB, Up: Configuration Notes

### C.2 Using DDD with Bash

BASH support is rather new. As a programming language, BASH is not feature rich: there are no record structures or hash tables (yet), no pointers, package variable scoping or methods. So much of the data display and visualization features of DDD are disabled.

As with any scripting or interpreted language like Perl, stepping a machine-language instructions (commands Stepi/Nexti) doesn't exist.

Some BASH settings are essential for DDD to work correctly. These settings with their correct values are:

         set annotate 1
         set prompt set prompt bashdb$_Dbg_less$_Dbg_greater$_Dbg_space

DDD sets these values automatically when invoking BASH; if these values are changed, there may be some malfunctions.

Pay special attention when the prompt has extra angle brackets (a nested shell) or has any parenthesis (is in a subshell). Quitting may merely exit out of one of these nested (sub)shells rather than leave the program.

Next: Ladebug, Previous: Bash, Up: Configuration Notes

### C.3 Using DDD with DBX

When used for debugging Pascal-like programs, DDD does not infer correct array subscripts and always starts to count with 1.

With some DBX versions (notably Solaris DBX), DDD strips C-style and C++-style comments from the DBX output in order to interpret it properly. This also affects the output of the debugged program when sent to the debugger console. Using the separate execution window avoids these problems.

In some DBX versions (notably DEC DBX and AIX DBX), there is no automatic data display. As an alternative, DDD uses the DBX ‘`print`’ command to access data values. This means that variable names are interpreted according to the current frame; variables outside the current frame cannot be displayed.

Next: JDB, Previous: DBX, Up: Configuration Notes

### C.4 Using DDD with Ladebug

All DBX limitations (see DBX) apply to Ladebug as well.

Next: Make, Previous: Ladebug, Up: Configuration Notes

### C.5 Using DDD with JDB

There is no automatic data display in JDB. As a workaround, DDD uses the ‘`dump`’ command to access data values. This means that variable names are interpreted according to the current frame; variables outside the current frame cannot be displayed.

In JDB 1.1, the ‘`dump`’ and ‘`print`’ commands do not support expression evaluation. Hence, you cannot display arbitrary expressions.

Parsing of JDB output is quite CPU-intensive, due to the recognition of asynchronous prompts (any thread may output anything at any time, including prompts). Hence, a program producing much console output is likely to slow down DDD considerably. In such a case, have the program run with `-debug` in a separate window and attach JDB to it using the `-passwd` option.

Next: Perl, Previous: JDB, Up: Configuration Notes

### C.6 Using DDD with GNU Make

GNU Make support is rather new. As a programming language, GNU Make is a bit of a stretch for DDD. There are no record structures or hash tables, no pointers. Well, actually this does exist, but the records, pointers and hash tables are fixed into the system. There are Makefile variables, “targets” (which sometimes refer to files), dependencies, and commands. There is sort of an “scope” that for variables too.

But much of the data display and visualization features of DDD are disabled. However `info locals` does work and you can hover over a variable and see its value.

As with any scripting or interpreted language like Perl, stepping a machine-language instructions (commands Stepi/Nexti) doesn't exist.

Pay special attention when the prompt has extra angle brackets—nested invocation of GNU MAKE. Quitting may merely exit out of one of these nested invocations rather than leave the program.

Next: Python, Previous: Make, Up: Configuration Notes

### C.7 Using DDD with Perl

There is no automatic data display in Perl. As a workaround, DDD uses the ‘`x`’ command to access data values. This means that variable names are interpreted according to the current frame; variables outside the current frame cannot be displayed.

Next: XDB, Previous: Perl, Up: Configuration Notes

### C.8 Using DDD with Python

In short, make sure you use a newer version of `pydb`, one from http://bashdb.sourceforge.net/pydb. Older versions that had been supplied with DDD will no longer work.

History: Up to around 1999 there was parallel development that went on between DDD's Python debugger `pydb` and the stock python debugger `pdb`. These were not necessarily competing efforts, just parallel. In fact the same person worked a little bit on both.

One feature that `pydb` supported that wasn't in `pdb` was GDB's `display` command.

After 1999, maintaining `pydb` more or less fell into disuse and `pdb` sort of inched ahead with bug fixes and redisigned interaces. Around the beginning of 2006, new work was started to enhance pdb and to make it more like GDB. Since DDD already understands a large set of GDB commands, many of these enhancements were immediately realizable by DDD. These things include command completion, restarting the debugger, and using set/show/info commands.

With the blessing of the original author of `pydb`, the new effort took over the name of the old one, Although it did not actually start out from the `pydb` base but from pdb adding the old `pydb` features.

Next: LessTif, Previous: Python, Up: Configuration Notes

### C.9 Using DDD with XDB

There is no automatic data display in XDB. As a workaround, DDD uses the ‘`p`’ command to access data values. This means that variable names are interpreted according to the current frame; variables outside the current frame cannot be displayed.

Previous: XDB, Up: Configuration Notes

### C.10 Using DDD with LessTif

DDD includes a number of hacks that make DDD run with LessTif, a free M*tif library without loss of functionality. Since a DDD binary may be dynamically bound and used with either an OSF/Motif or LessTif library, these lesstif hacks can be enabled and disabled at run time.

Whether the lesstif hacks are included at run-time depends on the setting of the ‘`lessTifVersion`’ resource:

— Resource: lessTifVersion (class LessTifVersion)

> Indicates the LessTif version DDD is running against. For LessTif version x.y, the value is x multiplied by 1000 plus y—for instance, the value `79` stands for LessTif 0.79 and the value `1005` stands for LessTif 1.5.

> If the value of this resource is less than 1000, indicating LessTif 0.99 or earlier, DDD enables version-specific hacks to make DDD work around LessTif bugs and deficiencies.

> If DDD was compiled against LessTif, the default value is the value of the ‘`LessTifVersion`’ macro in `<Xm/Xm.h>`. If DDD was compiled against OSF/Motif, the default value is `1000`, disabling all LessTif-specific hacks.

To set the ‘`lessTifVersion`’ resource at DDD invocation and to specify the version number of the LessTif library, you can also use the option `--lesstif-version` version.

The default value of the ‘`lessTifVersion`’ resource is derived from the LessTif library DDD was compiled against (or `1000` when compiled against OSF/Motif). Hence, you normally don't need to worry about the value of this resource. However, if you use a dynamically linked DDD binary with a library other than the one DDD was compiled against, you must specify the version number of the library using this resource. (Unfortunately, DDD cannot detect this at run-time.)

Here are a few scenarios to illustrate this scheme:

- Your DDD binary was compiled against OSF/Motif, but you use a LessTif 0.88 dynamic library instead. Invoke DDD with `--lesstif-version 88`.
- Your DDD binary was compiled against LessTif, but you use a OSF/Motif dynamic library instead. Invoke DDD with `--lesstif-version 1000`.
- Your DDD binary was compiled against LessTif 0.85, and you have upgraded to LessTif 0.90. Invoke DDD with `--lesstif-version 90`.

To find out the LessTif or OSF/Motif version DDD was compiled against, invoke DDD with the `--configuration` option.

In the DDD source, LessTif-specific hacks are controlled by the string ‘`lesstif_version`’.

Next: Extending, Previous: Configuration Notes, Up: Top

## Appendix D Dirty Tricks

Do you miss anything in this manual? Do you have any material that should be added? Please send any contributions to ddd@gnu.org.

Next: FAQ, Previous: Dirty Tricks, Up: Top

## Appendix E Extending DDD

If you have any contributions to be incorporated into DDD, please send them to ddd@gnu.org. For suggestions on what might be done, see the file ‘`TODO`’ in the DDD distribution.

Next: License, Previous: Extending, Up: Top

## Appendix F Frequently Answered Questions

See the DDD WWW page for frequently answered questions not covered in this manual.

Next: Help and Assistance, Previous: FAQ, Up: Top

## Appendix G GNU General Public License

Version 3, 29 June 2007

         Copyright © 2007 Free Software Foundation, Inc. http://fsf.org/

         Everyone is permitted to copy and distribute verbatim copies of this
         license document, but changing it is not allowed.

### Preamble

The GNU General Public License is a free, copyleft license for software and other kinds of works.

The licenses for most software and other practical works are designed to take away your freedom to share and change the works. By contrast, the GNU General Public License is intended to guarantee your freedom to share and change all versions of a program—to make sure it remains free software for all its users. We, the Free Software Foundation, use the GNU General Public License for most of our software; it applies also to any other work released this way by its authors. You can apply it to your programs, too.

When we speak of free software, we are referring to freedom, not price. Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software (and charge for them if you wish), that you receive source code or can get it if you want it, that you can change the software or use pieces of it in new free programs, and that you know you can do these things.

To protect your rights, we need to prevent others from denying you these rights or asking you to surrender the rights. Therefore, you have certain responsibilities if you distribute copies of the software, or if you modify it: responsibilities to respect the freedom of others.

For example, if you distribute copies of such a program, whether gratis or for a fee, you must pass on to the recipients the same freedoms that you received. You must make sure that they, too, receive or can get the source code. And you must show them these terms so they know their rights.

Developers that use the GNU GPL protect your rights with two steps: (1) assert copyright on the software, and (2) offer you this License giving you legal permission to copy, distribute and/or modify it.

For the developers' and authors' protection, the GPL clearly explains that there is no warranty for this free software. For both users' and authors' sake, the GPL requires that modified versions be marked as changed, so that their problems will not be attributed erroneously to authors of previous versions.

Some devices are designed to deny users access to install or run modified versions of the software inside them, although the manufacturer can do so. This is fundamentally incompatible with the aim of protecting users' freedom to change the software. The systematic pattern of such abuse occurs in the area of products for individuals to use, which is precisely where it is most unacceptable. Therefore, we have designed this version of the GPL to prohibit the practice for those products. If such problems arise substantially in other domains, we stand ready to extend this provision to those domains in future versions of the GPL, as needed to protect the freedom of users.

Finally, every program is threatened constantly by software patents. States should not allow patents to restrict development and use of software on general-purpose computers, but in those that do, we wish to avoid the special danger that patents applied to a free program could make it effectively proprietary. To prevent this, the GPL assures that patents cannot be used to render the program non-free.

The precise terms and conditions for copying, distribution and modification follow.

### TERMS AND CONDITIONS

0. Definitions.

   “This License” refers to version 3 of the GNU General Public License.

   “Copyright” also means copyright-like laws that apply to other kinds of works, such as semiconductor masks.

   “The Program” refers to any copyrightable work licensed under this License. Each licensee is addressed as “you”. “Licensees” and “recipients” may be individuals or organizations.

   To “modify” a work means to copy from or adapt all or part of the work in a fashion requiring copyright permission, other than the making of an exact copy. The resulting work is called a “modified version” of the earlier work or a work “based on” the earlier work.

   A “covered work” means either the unmodified Program or a work based on the Program.

   To “propagate” a work means to do anything with it that, without permission, would make you directly or secondarily liable for infringement under applicable copyright law, except executing it on a computer or modifying a private copy. Propagation includes copying, distribution (with or without modification), making available to the public, and in some countries other activities as well.

   To “convey” a work means any kind of propagation that enables other parties to make or receive copies. Mere interaction with a user through a computer network, with no transfer of a copy, is not conveying.

   An interactive user interface displays “Appropriate Legal Notices” to the extent that it includes a convenient and prominently visible feature that (1) displays an appropriate copyright notice, and (2) tells the user that there is no warranty for the work (except to the extent that warranties are provided), that licensees may convey the work under this License, and how to view a copy of this License. If the interface presents a list of user commands or options, such as a menu, a prominent item in the list meets this criterion.

1. Source Code.

   The “source code” for a work means the preferred form of the work for making modifications to it. “Object code” means any non-source form of a work.

   A “Standard Interface” means an interface that either is an official standard defined by a recognized standards body, or, in the case of interfaces specified for a particular programming language, one that is widely used among developers working in that language.

   The “System Libraries” of an executable work include anything, other than the work as a whole, that (a) is included in the normal form of packaging a Major Component, but which is not part of that Major Component, and (b) serves only to enable use of the work with that Major Component, or to implement a Standard Interface for which an implementation is available to the public in source code form. A “Major Component”, in this context, means a major essential component (kernel, window system, and so on) of the specific operating system (if any) on which the executable work runs, or a compiler used to produce the work, or an object code interpreter used to run it.

   The “Corresponding Source” for a work in object code form means all the source code needed to generate, install, and (for an executable work) run the object code and to modify the work, including scripts to control those activities. However, it does not include the work's System Libraries, or general-purpose tools or generally available free programs which are used unmodified in performing those activities but which are not part of the work. For example, Corresponding Source includes interface definition files associated with source files for the work, and the source code for shared libraries and dynamically linked subprograms that the work is specifically designed to require, such as by intimate data communication or control flow between those subprograms and other parts of the work.

   The Corresponding Source need not include anything that users can regenerate automatically from other parts of the Corresponding Source.

   The Corresponding Source for a work in source code form is that same work.

2. Basic Permissions.

   All rights granted under this License are granted for the term of copyright on the Program, and are irrevocable provided the stated conditions are met. This License explicitly affirms your unlimited permission to run the unmodified Program. The output from running a covered work is covered by this License only if the output, given its content, constitutes a covered work. This License acknowledges your rights of fair use or other equivalent, as provided by copyright law.

   You may make, run and propagate covered works that you do not convey, without conditions so long as your license otherwise remains in force. You may convey covered works to others for the sole purpose of having them make modifications exclusively for you, or provide you with facilities for running those works, provided that you comply with the terms of this License in conveying all material for which you do not control copyright. Those thus making or running the covered works for you must do so exclusively on your behalf, under your direction and control, on terms that prohibit them from making any copies of your copyrighted material outside their relationship with you.

   Conveying under any other circumstances is permitted solely under the conditions stated below. Sublicensing is not allowed; section 10 makes it unnecessary.

3. Protecting Users' Legal Rights From Anti-Circumvention Law.

   No covered work shall be deemed part of an effective technological measure under any applicable law fulfilling obligations under article 11 of the WIPO copyright treaty adopted on 20 December 1996, or similar laws prohibiting or restricting circumvention of such measures.

   When you convey a covered work, you waive any legal power to forbid circumvention of technological measures to the extent such circumvention is effected by exercising rights under this License with respect to the covered work, and you disclaim any intention to limit operation or modification of the work as a means of enforcing, against the work's users, your or third parties' legal rights to forbid circumvention of technological measures.

4. Conveying Verbatim Copies.

   You may convey verbatim copies of the Program's source code as you receive it, in any medium, provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice; keep intact all notices stating that this License and any non-permissive terms added in accord with section 7 apply to the code; keep intact all notices of the absence of any warranty; and give all recipients a copy of this License along with the Program.

   You may charge any price or no price for each copy that you convey, and you may offer support or warranty protection for a fee.

5. Conveying Modified Source Versions.

   You may convey a work based on the Program, or the modifications to produce it from the Program, in the form of source code under the terms of section 4, provided that you also meet all of these conditions:

   1. The work must carry prominent notices stating that you modified it, and giving a relevant date.
   2. The work must carry prominent notices stating that it is released under this License and any conditions added under section 7. This requirement modifies the requirement in section 4 to “keep intact all notices”.
   3. You must license the entire work, as a whole, under this License to anyone who comes into possession of a copy. This License will therefore apply, along with any applicable section 7 additional terms, to the whole of the work, and all its parts, regardless of how they are packaged. This License gives no permission to license the work in any other way, but it does not invalidate such permission if you have separately received it.
   4. If the work has interactive user interfaces, each must display Appropriate Legal Notices; however, if the Program has interactive interfaces that do not display Appropriate Legal Notices, your work need not make them do so.

   A compilation of a covered work with other separate and independent works, which are not by their nature extensions of the covered work, and which are not combined with it such as to form a larger program, in or on a volume of a storage or distribution medium, is called an “aggregate” if the compilation and its resulting copyright are not used to limit the access or legal rights of the compilation's users beyond what the individual works permit. Inclusion of a covered work in an aggregate does not cause this License to apply to the other parts of the aggregate.

6. Conveying Non-Source Forms.

   You may convey a covered work in object code form under the terms of sections 4 and 5, provided that you also convey the machine-readable Corresponding Source under the terms of this License, in one of these ways:

   1. Convey the object code in, or embodied in, a physical product (including a physical distribution medium), accompanied by the Corresponding Source fixed on a durable physical medium customarily used for software interchange.
   2. Convey the object code in, or embodied in, a physical product (including a physical distribution medium), accompanied by a written offer, valid for at least three years and valid for as long as you offer spare parts or customer support for that product model, to give anyone who possesses the object code either (1) a copy of the Corresponding Source for all the software in the product that is covered by this License, on a durable physical medium customarily used for software interchange, for a price no more than your reasonable cost of physically performing this conveying of source, or (2) access to copy the Corresponding Source from a network server at no charge.
   3. Convey individual copies of the object code with a copy of the written offer to provide the Corresponding Source. This alternative is allowed only occasionally and noncommercially, and only if you received the object code with such an offer, in accord with subsection 6b.
   4. Convey the object code by offering access from a designated place (gratis or for a charge), and offer equivalent access to the Corresponding Source in the same way through the same place at no further charge. You need not require recipients to copy the Corresponding Source along with the object code. If the place to copy the object code is a network server, the Corresponding Source may be on a different server (operated by you or a third party) that supports equivalent copying facilities, provided you maintain clear directions next to the object code saying where to find the Corresponding Source. Regardless of what server hosts the Corresponding Source, you remain obligated to ensure that it is available for as long as needed to satisfy these requirements.
   5. Convey the object code using peer-to-peer transmission, provided you inform other peers where the object code and Corresponding Source of the work are being offered to the general public at no charge under subsection 6d.

   A separable portion of the object code, whose source code is excluded from the Corresponding Source as a System Library, need not be included in conveying the object code work.

   A “User Product” is either (1) a “consumer product”, which means any tangible personal property which is normally used for personal, family, or household purposes, or (2) anything designed or sold for incorporation into a dwelling. In determining whether a product is a consumer product, doubtful cases shall be resolved in favor of coverage. For a particular product received by a particular user, “normally used” refers to a typical or common use of that class of product, regardless of the status of the particular user or of the way in which the particular user actually uses, or expects or is expected to use, the product. A product is a consumer product regardless of whether the product has substantial commercial, industrial or non-consumer uses, unless such uses represent the only significant mode of use of the product.

   “Installation Information” for a User Product means any methods, procedures, authorization keys, or other information required to install and execute modified versions of a covered work in that User Product from a modified version of its Corresponding Source. The information must suffice to ensure that the continued functioning of the modified object code is in no case prevented or interfered with solely because modification has been made.

   If you convey an object code work under this section in, or with, or specifically for use in, a User Product, and the conveying occurs as part of a transaction in which the right of possession and use of the User Product is transferred to the recipient in perpetuity or for a fixed term (regardless of how the transaction is characterized), the Corresponding Source conveyed under this section must be accompanied by the Installation Information. But this requirement does not apply if neither you nor any third party retains the ability to install modified object code on the User Product (for example, the work has been installed in ROM).

   The requirement to provide Installation Information does not include a requirement to continue to provide support service, warranty, or updates for a work that has been modified or installed by the recipient, or for the User Product in which it has been modified or installed. Access to a network may be denied when the modification itself materially and adversely affects the operation of the network or violates the rules and protocols for communication across the network.

   Corresponding Source conveyed, and Installation Information provided, in accord with this section must be in a format that is publicly documented (and with an implementation available to the public in source code form), and must require no special password or key for unpacking, reading or copying.

7. Additional Terms.

   “Additional permissions” are terms that supplement the terms of this License by making exceptions from one or more of its conditions. Additional permissions that are applicable to the entire Program shall be treated as though they were included in this License, to the extent that they are valid under applicable law. If additional permissions apply only to part of the Program, that part may be used separately under those permissions, but the entire Program remains governed by this License without regard to the additional permissions.

   When you convey a copy of a covered work, you may at your option remove any additional permissions from that copy, or from any part of it. (Additional permissions may be written to require their own removal in certain cases when you modify the work.) You may place additional permissions on material, added by you to a covered work, for which you have or can give appropriate copyright permission.

   Notwithstanding any other provision of this License, for material you add to a covered work, you may (if authorized by the copyright holders of that material) supplement the terms of this License with terms:

   1. Disclaiming warranty or limiting liability differently from the terms of sections 15 and 16 of this License; or
   2. Requiring preservation of specified reasonable legal notices or author attributions in that material or in the Appropriate Legal Notices displayed by works containing it; or
   3. Prohibiting misrepresentation of the origin of that material, or requiring that modified versions of such material be marked in reasonable ways as different from the original version; or
   4. Limiting the use for publicity purposes of names of licensors or authors of the material; or
   5. Declining to grant rights under trademark law for use of some trade names, trademarks, or service marks; or
   6. Requiring indemnification of licensors and authors of that material by anyone who conveys the material (or modified versions of it) with contractual assumptions of liability to the recipient, for any liability that these contractual assumptions directly impose on those licensors and authors.

   All other non-permissive additional terms are considered “further restrictions” within the meaning of section 10. If the Program as you received it, or any part of it, contains a notice stating that it is governed by this License along with a term that is a further restriction, you may remove that term. If a license document contains a further restriction but permits relicensing or conveying under this License, you may add to a covered work material governed by the terms of that license document, provided that the further restriction does not survive such relicensing or conveying.

   If you add terms to a covered work in accord with this section, you must place, in the relevant source files, a statement of the additional terms that apply to those files, or a notice indicating where to find the applicable terms.

   Additional terms, permissive or non-permissive, may be stated in the form of a separately written license, or stated as exceptions; the above requirements apply either way.

8. Termination.

   You may not propagate or modify a covered work except as expressly provided under this License. Any attempt otherwise to propagate or modify it is void, and will automatically terminate your rights under this License (including any patent licenses granted under the third paragraph of section 11).

   However, if you cease all violation of this License, then your license from a particular copyright holder is reinstated (a) provisionally, unless and until the copyright holder explicitly and finally terminates your license, and (b) permanently, if the copyright holder fails to notify you of the violation by some reasonable means prior to 60 days after the cessation.

   Moreover, your license from a particular copyright holder is reinstated permanently if the copyright holder notifies you of the violation by some reasonable means, this is the first time you have received notice of violation of this License (for any work) from that copyright holder, and you cure the violation prior to 30 days after your receipt of the notice.

   Termination of your rights under this section does not terminate the licenses of parties who have received copies or rights from you under this License. If your rights have been terminated and not permanently reinstated, you do not qualify to receive new licenses for the same material under section 10.

9. Acceptance Not Required for Having Copies.

   You are not required to accept this License in order to receive or run a copy of the Program. Ancillary propagation of a covered work occurring solely as a consequence of using peer-to-peer transmission to receive a copy likewise does not require acceptance. However, nothing other than this License grants you permission to propagate or modify any covered work. These actions infringe copyright if you do not accept this License. Therefore, by modifying or propagating a covered work, you indicate your acceptance of this License to do so.

10. Automatic Licensing of Downstream Recipients.

    Each time you convey a covered work, the recipient automatically receives a license from the original licensors, to run, modify and propagate that work, subject to this License. You are not responsible for enforcing compliance by third parties with this License.

    An “entity transaction” is a transaction transferring control of an organization, or substantially all assets of one, or subdividing an organization, or merging organizations. If propagation of a covered work results from an entity transaction, each party to that transaction who receives a copy of the work also receives whatever licenses to the work the party's predecessor in interest had or could give under the previous paragraph, plus a right to possession of the Corresponding Source of the work from the predecessor in interest, if the predecessor has it or can get it with reasonable efforts.

    You may not impose any further restrictions on the exercise of the rights granted or affirmed under this License. For example, you may not impose a license fee, royalty, or other charge for exercise of rights granted under this License, and you may not initiate litigation (including a cross-claim or counterclaim in a lawsuit) alleging that any patent claim is infringed by making, using, selling, offering for sale, or importing the Program or any portion of it.

11. Patents.

    A “contributor” is a copyright holder who authorizes use under this License of the Program or a work on which the Program is based. The work thus licensed is called the contributor's “contributor version”.

    A contributor's “essential patent claims” are all patent claims owned or controlled by the contributor, whether already acquired or hereafter acquired, that would be infringed by some manner, permitted by this License, of making, using, or selling its contributor version, but do not include claims that would be infringed only as a consequence of further modification of the contributor version. For purposes of this definition, “control” includes the right to grant patent sublicenses in a manner consistent with the requirements of this License.

    Each contributor grants you a non-exclusive, worldwide, royalty-free patent license under the contributor's essential patent claims, to make, use, sell, offer for sale, import and otherwise run, modify and propagate the contents of its contributor version.

    In the following three paragraphs, a “patent license” is any express agreement or commitment, however denominated, not to enforce a patent (such as an express permission to practice a patent or covenant not to sue for patent infringement). To “grant” such a patent license to a party means to make such an agreement or commitment not to enforce a patent against the party.

    If you convey a covered work, knowingly relying on a patent license, and the Corresponding Source of the work is not available for anyone to copy, free of charge and under the terms of this License, through a publicly available network server or other readily accessible means, then you must either (1) cause the Corresponding Source to be so available, or (2) arrange to deprive yourself of the benefit of the patent license for this particular work, or (3) arrange, in a manner consistent with the requirements of this License, to extend the patent license to downstream recipients. “Knowingly relying” means you have actual knowledge that, but for the patent license, your conveying the covered work in a country, or your recipient's use of the covered work in a country, would infringe one or more identifiable patents in that country that you have reason to believe are valid.

    If, pursuant to or in connection with a single transaction or arrangement, you convey, or propagate by procuring conveyance of, a covered work, and grant a patent license to some of the parties receiving the covered work authorizing them to use, propagate, modify or convey a specific copy of the covered work, then the patent license you grant is automatically extended to all recipients of the covered work and works based on it.

    A patent license is “discriminatory” if it does not include within the scope of its coverage, prohibits the exercise of, or is conditioned on the non-exercise of one or more of the rights that are specifically granted under this License. You may not convey a covered work if you are a party to an arrangement with a third party that is in the business of distributing software, under which you make payment to the third party based on the extent of your activity of conveying the work, and under which the third party grants, to any of the parties who would receive the covered work from you, a discriminatory patent license (a) in connection with copies of the covered work conveyed by you (or copies made from those copies), or (b) primarily for and in connection with specific products or compilations that contain the covered work, unless you entered into that arrangement, or that patent license was granted, prior to 28 March 2007.

    Nothing in this License shall be construed as excluding or limiting any implied license or other defenses to infringement that may otherwise be available to you under applicable patent law.

12. No Surrender of Others' Freedom.

    If conditions are imposed on you (whether by court order, agreement or otherwise) that contradict the conditions of this License, they do not excuse you from the conditions of this License. If you cannot convey a covered work so as to satisfy simultaneously your obligations under this License and any other pertinent obligations, then as a consequence you may not convey it at all. For example, if you agree to terms that obligate you to collect a royalty for further conveying from those to whom you convey the Program, the only way you could satisfy both those terms and this License would be to refrain entirely from conveying the Program.

13. Use with the GNU Affero General Public License.

    Notwithstanding any other provision of this License, you have permission to link or combine any covered work with a work licensed under version 3 of the GNU Affero General Public License into a single combined work, and to convey the resulting work. The terms of this License will continue to apply to the part which is the covered work, but the special requirements of the GNU Affero General Public License, section 13, concerning interaction through a network will apply to the combination as such.

14. Revised Versions of this License.

    The Free Software Foundation may publish revised and/or new versions of the GNU General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns.

    Each version is given a distinguishing version number. If the Program specifies that a certain numbered version of the GNU General Public License “or any later version” applies to it, you have the option of following the terms and conditions either of that numbered version or of any later version published by the Free Software Foundation. If the Program does not specify a version number of the GNU General Public License, you may choose any version ever published by the Free Software Foundation.

    If the Program specifies that a proxy can decide which future versions of the GNU General Public License can be used, that proxy's public statement of acceptance of a version permanently authorizes you to choose that version for the Program.

    Later license versions may give you additional or different permissions. However, no additional obligations are imposed on any author or copyright holder as a result of your choosing to follow a later version.

15. Disclaimer of Warranty.

    THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM “AS IS” WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.

16. Limitation of Liability.

    IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

17. Interpretation of Sections 15 and 16.

    If the disclaimer of warranty and limitation of liability provided above cannot be given local legal effect according to their terms, reviewing courts shall apply local law that most closely approximates an absolute waiver of all civil liability in connection with the Program, unless a warranty or assumption of liability accompanies a copy of the Program in return for a fee.

### END OF TERMS AND CONDITIONS

### How to Apply These Terms to Your New Programs

If you develop a new program, and you want it to be of the greatest possible use to the public, the best way to achieve this is to make it free software which everyone can redistribute and change under these terms.

To do so, attach the following notices to the program. It is safest to attach them to the start of each source file to most effectively state the exclusion of warranty; and each file should have at least the “copyright” line and a pointer to where the full notice is found.

         one line to give the program's name and a brief idea of what it does.
         Copyright (C) year name of author

         This program is free software: you can redistribute it and/or modify
         it under the terms of the GNU General Public License as published by
         the Free Software Foundation, either version 3 of the License, or (at
         your option) any later version.

         This program is distributed in the hope that it will be useful, but
         WITHOUT ANY WARRANTY; without even the implied warranty of
         MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
         General Public License for more details.

         You should have received a copy of the GNU General Public License
         along with this program.  If not, see http://www.gnu.org/licenses/.

Also add information on how to contact you by electronic and paper mail.

If the program does terminal interaction, make it output a short notice like this when it starts in an interactive mode:

         program Copyright (C) year name of author
         This program comes with ABSOLUTELY NO WARRANTY; for details type ‘show w’.
         This is free software, and you are welcome to redistribute it
         under certain conditions; type ‘show c’ for details.

The hypothetical commands ‘`show w`’ and ‘`show c`’ should show the appropriate parts of the General Public License. Of course, your program's commands might be different; for a GUI interface, you would use an “about box”.

You should also get your employer (if you work as a programmer) or school, if any, to sign a “copyright disclaimer” for the program, if necessary. For more information on this, and how to apply and follow the GNU GPL, see http://www.gnu.org/licenses/.

The GNU General Public License does not permit incorporating your program into proprietary programs. If your program is a subroutine library, you may consider it more useful to permit linking proprietary applications with the library. If this is what you want to do, use the GNU Lesser General Public License instead of this License. But first, please read http://www.gnu.org/philosophy/why-not-lgpl.html.

Next: Documentation License, Previous: License, Up: Top

## Appendix H Help and Assistance

We have set up a mailing list for general DDD discussions. If you need help and assistance for solving a DDD problem, you find the right people here.

Send message to all receivers of the mailing list to:

         ddd@gnu.org

This mailing list is also the place where new DDD releases are announced. If you want to subscribe the list, or get more information, send a mail to

         ddd-request@gnu.org

See also the DDD WWW page for recent announcements and other news related to DDD.

Next: Label Index, Previous: Help and Assistance, Up: Top

## Appendix I GNU Free Documentation License

Version 1.1, March 2000

         Copyright (C) 2000  Free Software Foundation, Inc.
         59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

         Everyone is permitted to copy and distribute verbatim copies
         of this license document, but changing it is not allowed.

0. PREAMBLE

   The purpose of this License is to make a manual, textbook, or other written document “free” in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.

   This License is a kind of “copyleft”, which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.

   We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.

1. APPLICABILITY AND DEFINITIONS

   This License applies to any manual or other work that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. The “Document”, below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as “you”.

   A “Modified Version” of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language.

   A “Secondary Section” is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document's overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (For example, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) The relationship could be a matter of historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them.

   The “Invariant Sections” are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License.

   The “Cover Texts” are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is released under this License.

   A “Transparent” copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, whose contents can be viewed and edited directly and straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup has been designed to thwart or discourage subsequent modification by readers is not Transparent. A copy that is not “Transparent” is called “Opaque”.

   Examples of suitable formats for Transparent copies include plain ASCII without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD, and standard-conforming simple HTML designed for human modification. Opaque formats include PostScript, PDF, proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML produced by some word processors for output purposes only.

   The “Title Page” means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, “Title Page” means the text near the most prominent appearance of the work's title, preceding the beginning of the body of the text.

2. VERBATIM COPYING

   You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3.

   You may also lend copies, under the same conditions stated above, and you may publicly display copies.

3. COPYING IN QUANTITY

   If you publish printed copies of the Document numbering more than 100, and the Document's license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects.

   If the required texts for either cover are too voluminous to fit legibly, you should put the first ones listed (as many as fit reasonably) on the actual cover, and continue the rest onto adjacent pages.

   If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copy along with each Opaque copy, or state in or with each Opaque copy a publicly-accessible computer-network location containing a complete Transparent copy of the Document, free of added material, which the general network-using public has access to download anonymously at no charge using public-standard network protocols. If you use the latter option, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents or retailers) of that edition to the public.

   It is requested, but not required, that you contact the authors of the Document well before redistributing any large number of copies, to give them a chance to provide you with an updated version of the Document.

4. MODIFICATIONS

   You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version:

   A. Use in the Title Page (and on the covers, if any) a title distinct from that of the Document, and from those of previous versions (which should, if there were any, be listed in the History section of the Document). You may use the same title as a previous version if the original publisher of that version gives permission.
   B. List on the Title Page, as authors, one or more persons or entities responsible for authorship of the modifications in the Modified Version, together with at least five of the principal authors of the Document (all of its principal authors, if it has less than five).
   C. State on the Title page the name of the publisher of the Modified Version, as the publisher.
   D. Preserve all the copyright notices of the Document.
   E. Add an appropriate copyright notice for your modifications adjacent to the other copyright notices.
   F. Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the Addendum below.
   G. Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document's license notice.
   H. Include an unaltered copy of this License.
   I. Preserve the section entitled “History”, and its title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page. If there is no section entitled “History” in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence.
   J. Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document for previous versions it was based on. These may be placed in the “History” section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to gives permission.
   K. In any section entitled “Acknowledgements” or “Dedications”, preserve the section's title, and preserve in the section all the substance and tone of each of the contributor acknowledgements and/or dedications given therein.
   L. Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles. Section numbers or the equivalent are not considered part of the section titles.
   M. Delete any section entitled “Endorsements”. Such a section may not be included in the Modified Version.
   N. Do not retitle any existing section as “Endorsements” or to conflict in title with any Invariant Section.

   If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document, you may at your option designate some or all of these sections as invariant. To do this, add their titles to the list of Invariant Sections in the Modified Version's license notice. These titles must be distinct from any other section titles.

   You may add a section entitled “Endorsements”, provided it contains nothing but endorsements of your Modified Version by various parties–for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.

   You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.

   The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.

5. COMBINING DOCUMENTS

   You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice.

   The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work.

   In the combination, you must combine any sections entitled “History” in the various original documents, forming one section entitled “History”; likewise combine any sections entitled “Acknowledgements”, and any sections entitled “Dedications”. You must delete all sections entitled “Endorsements.”

6. COLLECTIONS OF DOCUMENTS

   You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.

   You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.

7. AGGREGATION WITH INDEPENDENT WORKS

   A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, does not as a whole count as a Modified Version of the Document, provided no compilation copyright is claimed for the compilation. Such a compilation is called an “aggregate”, and this License does not apply to the other self-contained works thus compiled with the Document, on account of their being thus compiled, if they are not themselves derivative works of the Document.

   If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one quarter of the entire aggregate, the Document's Cover Texts may be placed on covers that surround only the Document within the aggregate. Otherwise they must appear on covers around the whole aggregate.

8. TRANSLATION

   Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License provided that you also include the original English version of this License. In case of a disagreement between the translation and the original English version of this License, the original English version will prevail.

9. TERMINATION

   You may not copy, modify, sublicense, or distribute the Document except as expressly provided for under this License. Any other attempt to copy, modify, sublicense or distribute the Document is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.

10. FUTURE REVISIONS OF THIS LICENSE

    The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See http://www.gnu.org/copyleft/.

    Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License “or any later version” applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation.

### ADDENDUM: How to use this License for your documents

To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:

           Copyright (C)  year  your name.
           Permission is granted to copy, distribute and/or modify this document
           under the terms of the GNU Free Documentation License, Version 1.1
           or any later version published by the Free Software Foundation;
           with the Invariant Sections being list their titles, with the
           Front-Cover Texts being list, and with the Back-Cover Texts being list.
           A copy of the license is included in the section entitled ``GNU
           Free Documentation License''.

If you have no Invariant Sections, write “with no Invariant Sections” instead of saying which ones are invariant. If you have no Front-Cover Texts, write “no Front-Cover Texts” instead of “Front-Cover Texts being list”; likewise for Back-Cover Texts.

If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.

Next: Key Index, Previous: Documentation License, Up: Top

## Label Index

- `()`: GDB Argument Commands
- `3-D Lines`: Plot Appearance
- `Abort`: Program Menu
- `Abort`: Quitting
- `About DDD`: Help Menu
- `Align on Grid`: Data Menu
- `All Signals`: Signals
- `Apply`: Commands Menu
- `Attach`: Attaching to a Process
- `Attach to Process`: Attaching to a Process
- `Attach to Process`: File Menu
- `Auto-align Displays on Nearest Grid Point`: Aligning Displays
- `Automatic Display of Button Hints`: Button tips
- `Automatic Display of Variable Values`: Value Tips
- `Backtrace`: Status Menu
- `Bash Console`: View Menu
- `Bash Reference`: Getting Help
- `Bash Reference`: Help Menu
- `Break`: Setting Breakpoints
- `Break`: Tool Bar
- `Breakpoints`: Source Menu
- `Button`: GDB Simple Commands
- `Cache Machine Code`: Customizing Machine Code
- `Cache source files`: Customizing Source Lookup
- `Change Directory`: Working Directory
- `Change Directory`: File Menu
- `Clear`: Disabling Breakpoints
- `Clear`: Deleting Breakpoints
- `Clear`: Tool Bar
- `Clear`: Edit Menu
- `Clear Line`: Commands Menu
- `Clear Undo Buffer`: Customizing Undo
- `Clear Window`: Commands Menu
- `Close`: File Menu
- `Close data window when deleting last display`: Deleting Displays
- `Cluster`: Clustering
- `Cluster Data Displays`: Clustering
- `clustered`: Clustering
- `Color`: Printing the Graph
- `Command`: GDB Simple Commands
- `Command`: Entering Plotting Commands
- `Command History`: Commands Menu
- `Command Tool`: View Menu
- `Commands`: Commands Menu
- `Commands`: Menu Bar
- `Complete`: Commands Menu
- `Cont`: Command Tool
- `Continue`: Continuing Somewhere Else
- `Continue`: Resuming Execution
- `Continue`: Program Menu
- `Continue Automatically when Mouse Pointer is Frozen`: Stopping X Programs
- `Continue Until Here`: Temporary Breakpoints
- `Continue Without Signal`: Signals
- `Continue Without Signal`: Program Menu
- `Contour`: Plot Appearance
- `Copy`: Deleting Displays
- `Copy`: Edit Menu
- `Ctrl+A is`: Customizing the Edit Menu
- `Ctrl+C is`: Customizing the Edit Menu
- `Cut`: Deleting Displays
- `Cut`: Edit Menu
- `Data`: Data Menu
- `Data`: Menu Bar
- `Data Scrolling`: Scrolling Data
- `Data Window`: View Menu
- `DBX Console`: View Menu
- `DBX Reference`: Getting Help
- `DBX Reference`: Help Menu
- `DBX Settings`: Edit Menu
- `DDD License`: Help Menu
- `DDD News`: Help Menu
- `DDD Reference`: Getting Help
- `DDD Reference`: Help Menu
- `DDD Splash Screen`: Splash Screen
- `DDD WWW Page`: Getting Help
- `DDD WWW Page`: Help Menu
- `Debug DDD`: Maintenance Menu
- `Debugger Reference`: Getting Help
- `Debugger Reference`: Help Menu
- `Debugger Settings`: Edit Menu
- `Debugger Type`: Debugger Invocation
- `Define Command`: Commands Menu
- `Delete`: Editing Breakpoint Properties
- `Delete`: Deleting Breakpoints
- `Delete`: Edit Menu
- `Delete`: Deleting Sessions
- `Delete Breakpoint`: Deleting Breakpoints
- `Detach Process`: Attaching to a Process
- `Detach Process`: File Menu
- `Detect Aliases`: Shared Structures
- `Detect Aliases`: Data Menu
- `Determine Automatically from Arguments`: Debugger Invocation
- `Disable`: Editing Breakpoint Properties
- `Disable`: Disabling Breakpoints
- `Disable Breakpoint`: Disabling Breakpoints
- `Disp *`: Dereferencing Pointers
- `Display`: Creating Single Displays
- `Display`: Display Basics
- `Display`: Tool Bar
- `Display ()`: Data Menu
- `Display *`: Dereferencing Pointers
- `Display *()`: Dereferencing Pointers
- `Display Arguments`: Displaying Local Variables
- `Display Arguments`: Data Menu
- `Display Line Numbers`: Source Menu
- `Display Local Variables`: Displaying Local Variables
- `Display Local Variables`: Data Menu
- `Display Machine Code`: Source Menu
- `Display Source Line Numbers`: Customizing Source Appearance
- `Display Two-Dimensional Arrays as Tables`: Arrays as Tables
- `Displays`: Data Menu
- `Do Nothing`: Maintenance Menu
- `Down`: Selecting a frame
- `Down`: Command Tool
- `Down`: Status Menu
- `Dump Core`: Maintenance Menu
- `Dump Core Now`: Maintenance Menu
- `Edit`: Editing Source Code
- `Edit`: Command Tool
- `Edit`: Edit Menu
- `Edit`: Menu Bar
- `Edit <<`: GDB Simple Commands
- `Edit >>`: GDB Simple Commands
- `Edit >>`: Breakpoint Commands
- `Edit Buttons`: Defining Buttons
- `Edit Buttons`: Commands Menu
- `Edit Menu`: Display Shortcuts
- `Edit Source`: Editing Source Code
- `Edit Source`: Source Menu
- `Edit Sources`: Editing Source Code
- `Edit Themes`: Editing Themes
- `Enable`: Editing Breakpoint Properties
- `Enable`: Disabling Breakpoints
- `Enable Breakpoint`: Disabling Breakpoints
- `Enable supported buttons only`: Defining Buttons
- `End`: GDB Simple Commands
- `End`: Breakpoint Commands
- `Execute`: GDB Simple Commands
- `Execution Window`: Customizing the Execution Window
- `Execution Window`: View Menu
- `Exit`: File Menu
- `Exit`: Quitting
- `File`: File Menu
- `File`: Menu Bar
- `File Name`: Printing the Graph
- `Find <<`: Textual Search
- `Find << ()`: Source Menu
- `Find >>`: Textual Search
- `Find >>`: Tool Bar
- `Find >> ()`: Source Menu
- `Find Backward`: Commands Menu
- `Find Case Sensitive`: Source Menu
- `Find Forward`: Commands Menu
- `Find Words Only`: Textual Search
- `Find Words Only`: Source Menu
- `Finish`: Resuming Execution
- `Finish`: Command Tool
- `Finish`: Program Menu
- `GDB Console`: View Menu
- `GDB Reference`: Getting Help
- `GDB Reference`: Help Menu
- `GDB Settings`: Edit Menu
- `Get Core File`: Customizing Sessions
- `GNU Make Console`: View Menu
- `Green background`: Using Data Themes
- `Help`: Getting Help
- `Help`: Help Menu
- `Help`: Menu Bar
- `Hide`: Showing and Hiding Details
- `Hide`: Tool Bar
- `Iconify all windows at once`: Icons
- `Ignore Count`: Breakpoint Ignore Counts
- `Include Core Dump`: Saving Sessions
- `Intel x86 flab gits and registers`: Using Data Themes
- `Interrupt`: Interrupting
- `Interrupt`: Command Tool
- `Interrupt`: Program Menu
- `JDB Console`: View Menu
- `JDB Reference`: Getting Help
- `JDB Reference`: Help Menu
- `JDB Settings`: Edit Menu
- `Kill`: Killing the Program
- `Kill`: Command Tool
- `Kill`: Program Menu
- `Ladebug Console`: View Menu
- `Ladebug Reference`: Getting Help
- `Ladebug Reference`: Help Menu
- `Ladebug Settings`: Edit Menu
- `Landscape`: Printing Plots
- `Layout Graph`: Automatic Layout
- `Layout Graph`: Data Menu
- `Left to right`: Placement
- `List Processes`: Attaching to a Process
- `Lookup`: Editing Breakpoint Properties
- `Lookup`: Looking up Definitions
- `Lookup`: Tool Bar
- `Lookup ()`: Source Menu
- `Machine Code Indentation`: Customizing Machine Code
- `Machine Code Window`: View Menu
- `Maintenance`: Maintenance Menu
- `Maintenance`: Menu Bar
- `Make`: Recompiling
- `Make`: Command Tool
- `Make`: File Menu
- `Memory`: Examining Memory
- `Memory`: Data Menu
- `New Display`: Display Shortcuts
- `New Game`: Maintenance Menu
- `Next`: Resuming Execution
- `Next`: Command Tool
- `Next`: Commands Menu
- `Next`: Program Menu
- `Next Instruction`: Machine Code Execution
- `Next Instruction`: Program Menu
- `Nexti`: Machine Code Execution
- `Nexti`: Command Tool
- `On item`: Help Menu
- `Open`: Opening Source Files
- `Open`: Opening Core Dumps
- `Open`: Opening Programs
- `Open Class`: Opening Programs
- `Open Class`: File Menu
- `Open Core Dump`: File Menu
- `Open Program`: Attaching to a Process
- `Open Program`: Opening Programs
- `Open Program`: File Menu
- `Open Recent`: Opening Programs
- `Open Recent`: File Menu
- `Open Session`: File Menu
- `Open Session`: Resuming Sessions
- `Open Source`: Opening Source Files
- `Open Source`: File Menu
- `Orientation`: Printing the Graph
- `Other`: Display Shortcuts
- `Overview`: Help Menu
- `Paper Size`: Printing Plots
- `Paper Size`: Printing the Graph
- `Pass`: Signals
- `Paste`: Deleting Displays
- `Paste`: Edit Menu
- `Perl Console`: View Menu
- `Perl Reference`: Getting Help
- `Perl Reference`: Help Menu
- `Perl Settings`: Edit Menu
- `Placement`: Clustering
- `Placement`: Placement
- `Plot`: Gnuplot Invocation
- `Plot`: Plot Appearance
- `Plot`: Tool Bar
- `Plot Window`: Gnuplot Invocation
- `Portrait`: Printing Plots
- `Preferences`: Edit Menu
- `Previous`: Commands Menu
- `Print`: Printing Values
- `Print`: Signals
- `Print`: Editing all Watchpoints
- `Print`: Editing Watchpoint Properties
- `Print`: Tool Bar
- `Print ()`: Data Menu
- `Print Command`: Printing the Graph
- `Print Graph`: Printing the Graph
- `Print Graph`: File Menu
- `Print Plot`: Printing Plots
- `Program`: Program Menu
- `Program`: Menu Bar
- `PYDB Console`: View Menu
- `PYDB Reference`: Getting Help
- `PYDB Reference`: Help Menu
- `PYDB Settings`: Edit Menu
- `Quit Search`: Commands Menu
- `Record`: GDB Simple Commands
- `Record`: Breakpoint Commands
- `Red Background`: Applying Data Themes to Several Values
- `Red Background`: Using Data Themes
- `Redo`: Undoing Program Execution
- `Redo`: Looking up Previous Locations
- `Redo`: Undo and Redo
- `Redo`: Command Tool
- `Redo`: Edit Menu
- `Refer to Program Sources`: Customizing Source Lookup
- `Refresh`: Data Menu
- `Refresh Displays`: Repeated Values
- `Refresh Displays`: Refreshing the Data Window
- `Registers`: Registers
- `Registers`: Status Menu
- `Reload Source`: Editing Source Code
- `Reload Source`: Source Menu
- `Remove Menu`: Maintenance Menu
- `Reset`: Signals
- `Restart`: File Menu
- `Rotate`: Tool Bar
- `Rotate Graph`: Rotating the Graph
- `Rotate Graph`: Data Menu
- `Run`: Starting Program Execution
- `Run`: Command Tool
- `Run`: Program Menu
- `Run Again`: Starting Program Execution
- `Run Again`: Program Menu
- `Run in Execution Window`: Using the Execution Window
- `Run in Execution Window`: Program Menu
- `Save Data As`: Exporting Plot Data
- `Save Options`: Signals
- `Save Options`: Edit Menu
- `Save Session As`: Signals
- `Save Session As`: File Menu
- `Save Session As`: Saving Sessions
- `Scale`: Plot Appearance
- `Search path for source files`: Source Path
- `Select All`: Edit Menu
- `Selected Only`: Printing Plots
- `Selected Only`: Printing the Graph
- `Send`: Signals
- `Set`: Assignment
- `Set`: Tool Bar
- `Set Execution Position`: Continuing Somewhere Else
- `Set Temporary Breakpoint`: Temporary Breakpoints
- `Set Value`: Assignment
- `Show`: Showing and Hiding Details
- `Show`: Tool Bar
- `Show All`: Showing and Hiding Details
- `Show Just`: Showing and Hiding Details
- `Show More`: Showing and Hiding Details
- `Show Position and Breakpoints`: Customizing Glyphs
- `Signals`: Signals
- `Signals`: Status Menu
- `Small Titles`: Using Data Themes
- `Small Values`: Using Data Themes
- `Source`: Source Menu
- `Source`: Menu Bar
- `Source indentation`: Customizing Source Appearance
- `Source Window`: View Menu
- `Status`: Status Menu
- `Status`: Menu Bar
- `Status Displays`: Displaying Program Status
- `Status Displays`: Data Menu
- `Step`: Resuming Execution
- `Step`: Command Tool
- `Step`: Program Menu
- `Step Instruction`: Machine Code Execution
- `Step Instruction`: Program Menu
- `Stepi`: Machine Code Execution
- `Stepi`: Command Tool
- `Stop`: Signals
- `Suppress Values`: Using Data Themes
- `Suppress Values`: Deleting Displays
- `Suppress X warnings`: X Warnings
- `Tab Width`: Customizing Source Appearance
- `Temp`: Editing Breakpoint Properties
- `Theme`: Using Data Themes
- `Themes`: Editing Themes
- `Threads`: Threads
- `Threads`: Status Menu
- `Threshold for repeated print elements`: Repeated Values
- `Tic Tac Toe`: Maintenance Menu
- `Tiny Values`: Using Data Themes
- `Tip of the Day`: Help Menu
- `Tool Bar Appearance`: Window Layout
- `Tool Buttons Location`: Disabling the Command Tool
- `Top to bottom`: Placement
- `Uncluster`: Clustering
- `Uncompress`: Help Helpers
- `Undisp`: Deleting Displays
- `Undisp`: Tool Bar
- `Undisplay`: Display Basics
- `Undo`: Deleting Displays
- `Undo`: Showing and Hiding Details
- `Undo`: Undoing Program Execution
- `Undo`: Selecting a frame
- `Undo`: Looking up Previous Locations
- `Undo`: Undo and Redo
- `Undo`: Command Tool
- `Undo`: Edit Menu
- `Undo Buffer Size`: Customizing Undo
- `Uniconify When Ready`: Program Stop
- `Until`: Resuming Execution
- `Until`: Command Tool
- `Until`: Program Menu
- `Unwatch`: Tool Bar
- `Up`: Selecting a frame
- `Up`: Command Tool
- `Up`: Status Menu
- `View`: Plot Appearance
- `View`: View Menu
- `View`: Menu Bar
- `Warn if Multiple DDD Instances are Running`: Multiple Instances
- `Watch`: Editing Watchpoint Properties
- `Watch`: Setting Watchpoints
- `Watch`: Tool Bar
- `Watchpoints`: Data Menu
- `Web Browser`: Help Helpers
- `What Now?`: Getting Help
- `What Now?`: Help Menu
- `When DDD Crashes`: Maintenance Menu
- `Window Layout`: Window Layout
- `Writing into executable and core files`: Patching
- `XDB Console`: View Menu
- `XDB Reference`: Getting Help
- `XDB Reference`: Help Menu
- `XDB Settings`: Edit Menu

Next: Command Index, Previous: Label Index, Up: Top

## Key Index

- `Alt+1`: View Menu
- `Alt+2`: View Menu
- `Alt+3`: View Menu
- `Alt+4`: Source Menu
- `Alt+4`: View Menu
- `Alt+8`: View Menu
- `Alt+9`: View Menu
- `Alt+A`: Data Menu
- `Alt+G`: Data Menu
- `Alt+I`: Source Menu
- `Alt+L`: Data Menu
- `Alt+N`: Source Menu
- `Alt+R`: Data Menu
- `Alt+U`: Data Menu
- `Alt+W`: Source Menu
- `Alt+Y`: Data Menu
- `Ctrl+,`: Source Menu
- `Ctrl+-`: Data Menu
- `Ctrl+.`: Source Menu
- `Ctrl+/`: Source Menu
- `Ctrl+=`: Data Menu
- `Ctrl+\`: Program Menu
- `Ctrl+\`: Quitting
- `Ctrl+A`: Edit Menu
- `Ctrl+B`: Command History
- `Ctrl+B`: Commands Menu
- `Ctrl+C`: Interrupting
- `Ctrl+C`: Customizing the Edit Menu
- `Ctrl+C`: Program Menu
- `Ctrl+C`: Edit Menu
- `Ctrl+C`: Quitting
- `Ctrl+D`: Quitting
- `Ctrl+Down`: Selecting a frame
- `Ctrl+Down`: Status Menu
- `Ctrl+F`: Command History
- `Ctrl+F`: Commands Menu
- `Ctrl+F1`: Getting Help
- `Ctrl+Ins`: Edit Menu
- `Ctrl+L`: Data Menu
- `Ctrl+M`: File Menu
- `Ctrl+N`: File Menu
- `Ctrl+O`: File Menu
- `Ctrl+Q`: File Menu
- `Ctrl+Q`: Quitting
- `Ctrl+Q`: Invocation
- `Ctrl+S`: File Menu
- `Ctrl+Shift+A`: Customizing the Edit Menu
- `Ctrl+Shift+A`: Edit Menu
- `Ctrl+U`: Commands Menu
- `Ctrl+U`: Edit Menu
- `Ctrl+Up`: Selecting a frame
- `Ctrl+Up`: Status Menu
- `Ctrl+V`: Edit Menu
- `Ctrl+W`: File Menu
- `Ctrl+X`: Edit Menu
- `Ctrl+Y`: Edit Menu
- `Ctrl+Z`: Edit Menu
- `Down`: Command History
- `Down`: Moving Displays
- `Down`: Selecting Displays
- `Down`: Commands Menu
- `ESC`: Command History
- `ESC`: Interrupting
- `ESC`: Customizing the Edit Menu
- `Esc`: Commands Menu
- `Esc`: Program Menu
- `ESC`: Quitting
- `F1`: Getting Help
- `F12`: Maintenance Menu
- `F2`: Program Menu
- `F3`: Program Menu
- `F4`: Program Menu
- `F5`: Program Menu
- `F6`: Program Menu
- `F7`: Program Menu
- `F8`: Program Menu
- `F9`: Program Menu
- `Home`: Customizing the Edit Menu
- `Left`: Moving Displays
- `Left`: Selecting Displays
- `Return`: Command History
- `Return`: Commands Menu
- `Right`: Moving Displays
- `Right`: Selecting Displays
- `Shift`: Selecting Displays
- `Shift+Ctrl+L`: Source Menu
- `Shift+Ctrl+U`: Commands Menu
- `Shift+Ctrl+V`: Source Menu
- `Shift+Del`: Edit Menu
- `Shift+F5`: Program Menu
- `Shift+F6`: Program Menu
- `Shift+F9`: Program Menu
- `Shift+Ins`: Edit Menu
- `TAB`: Tool Bar
- `Tab`: Commands Menu
- `Up`: Command History
- `Up`: Moving Displays
- `Up`: Selecting Displays
- `Up`: Commands Menu

Next: Resource Index, Previous: Key Index, Up: Top

## Command Index

- `cont`: Undoing Program Execution
- `cont`: Customizing Grab Checking
- `contuntil`: GDB Argument Commands
- `directory`: Source Path
- `down`: Selecting a frame
- `file`: Remote Program
- `gcore`: Customizing Sessions
- `gd`: Commands with Other Debuggers
- `graph apply theme`: Applying Data Themes to Several Values
- `graph disable display`: Showing and Hiding Details
- `graph display`: Displaying Program Status
- `graph display`: Creating Single Displays
- `graph enable display`: Showing and Hiding Details
- `graph plot`: Plotting Arrays
- `graph refresh`: Refreshing the Data Window
- `graph toggle theme`: Applying Data Themes to Several Values
- `graph unapply theme`: Applying Data Themes to Several Values
- `gunzip`: Help Helpers
- `gzip`: Help Helpers
- `hbreak`: Hardware-Assisted Breakpoints
- `help`: Getting Help
- `kill`: Customizing Grab Checking
- `mwm`: Gnuplot Invocation
- `print`: Printing Values
- `quit`: Customizing Grab Checking
- `quit`: Quitting
- `remsh`: Remote Debugger
- `replot`: Entering Plotting Commands
- `rsh`: Remote Debugger
- `run`: Starting Program Execution
- `set environment`: Environment
- `set output`: Entering Plotting Commands
- `set term`: Entering Plotting Commands
- `target remote`: Remote Program
- `thbreak`: Hardware-Assisted Breakpoints
- `tty`: Debugger Communication
- `unset environment`: Environment
- `up`: Selecting a frame
- `zcat`: Help Helpers

Next: File Index, Previous: Command Index, Up: Top

## Resource Index

- `activeButtonColorKey`: Customizing the Tool Bar
- `align2dArrays`: Arrays as Tables
- `appDefaultsVersion`: Customizing Diagnostics
- `arrayOrientation`: Rotating Displays
- `autoCloseDataWindow`: Display Resources
- `autoDebugger`: Debugger Invocation
- `autoRaiseMenu`: Auto-Raise Menus
- `autoRaiseMenuDelay`: Auto-Raise Menus
- `autoRaiseTool`: Customizing Tool Position
- `bash`: GNU Make Initialization
- `bash`: Bash Initialization
- `bashDisplayShortcuts`: Display Shortcuts
- `bashInitCommands`: Bash Initialization
- `blockTTYInput`: Debugger Communication
- `break_at`: Images
- `bufferGDBOutput`: Debugger Communication
- `bumpDisplays`: Display Resources
- `buttonCaptionGeometry`: Customizing the Tool Bar
- `buttonCaptions`: Customizing the Tool Bar
- `buttonColorKey`: Customizing the Tool Bar
- `buttonDocs`: Button tips
- `buttonImageGeometry`: Customizing the Tool Bar
- `buttonImages`: Customizing the Tool Bar
- `buttonTips`: Button tips
- `cacheGlyphImages`: Customizing Glyphs
- `cacheMachineCode`: Customizing Machine Code
- `cacheSourceFiles`: Customizing Source Lookup
- `checkConfiguration`: Customizing Diagnostics
- `checkGrabDelay`: Customizing Grab Checking
- `checkGrabs`: Customizing Grab Checking
- `checkOptions`: Multiple Instances
- `CLASSPATH`: Source Path
- `clear_at`: Images
- `clusterDisplays`: Display Resources
- `commandToolBar`: Disabling the Command Tool
- `commonToolBar`: Window Layout
- `consoleButtons`: Customizing Buttons
- `consoleHasFocus`: Typing in the Source Window
- `contInterruptDelay`: Debugger Communication
- `cutCopyPasteBindings`: Customizing the Edit Menu
- `dataButtons`: Customizing Buttons
- `dataFont`: Customizing Fonts
- `dataFontSize`: Customizing Fonts
- `dbxDisplayShortcuts`: Display Shortcuts
- `dbxInitCommands`: DBX Initialization
- `dbxSettings`: DBX Initialization
- `ddd`: Images
- `DDD`: Environment
- `DDD_NO_SIGNAL_HANDLERS`: Debugging <acronym>DDD</acronym>
- `DDD_SESSION`: Resources
- `DDD_SESSIONS`: Customizing Sessions
- `DDD_STATE`: Resources
- `dddinitVersion`: Customizing Diagnostics
- `debugCoreDumps`: Customizing Diagnostics
- `debugger`: Debugger Invocation
- `debuggerCommand`: Debugger Invocation
- `decorateTool`: Customizing Tool Decoration
- `defaultFont`: Customizing Fonts
- `defaultFontSize`: Customizing Fonts
- `delete`: Images
- `deleteAliasDisplays`: Shared Structures
- `detectAliases`: Shared Structures
- `disable`: Images
- `disassemble`: Customizing Machine Code
- `display`: Images
- `DISPLAY`: Remote Host
- `DISPLAY`: X Options
- `displayGlyphs`: Customizing Glyphs
- `displayLineNumbers`: Customizing Source Appearance
- `displayPlacement`: Placement
- `displayTimeout`: Debugger Communication
- `dispref`: Images
- `drag_arrow`: Images
- `drag_cond`: Images
- `drag_stop`: Images
- `drag_temp`: Images
- `dumpCore`: Customizing Diagnostics
- `editCommand`: Customizing Editing
- `EDITOR`: Customizing Editing
- `enable`: Images
- `expandRepeatedValues`: Repeated Values
- `filterFiles`: Customizing File Filtering
- `find_backward`: Images
- `find_forward`: Images
- `findCaseSensitive`: Customizing Searching
- `findWordsOnly`: Customizing Searching
- `fixedWidthFont`: Customizing Fonts
- `fixedWidthFontSize`: Customizing Fonts
- `flatDialogButtons`: Customizing the Tool Bar
- `flatToolbarButtons`: Customizing the Tool Bar
- `fontSelectCommand`: Customizing Fonts
- `gdbDisplayShortcuts`: Display Shortcuts
- `gdbInitCommands`: GDB Initialization
- `gdbSettings`: GDB Initialization
- `getCoreCommand`: Customizing Sessions
- `globalTabCompletion`: Command Completion
- `glyphUpdateDelay`: Customizing Glyphs
- `grabAction`: Customizing Grab Checking
- `grabActionDelay`: Customizing Grab Checking
- `grey_arrow`: Images
- `grey_cond`: Images
- `grey_stop`: Images
- `grey_temp`: Images
- `groupIconify`: Icons
- `hide`: Images
- `hideInactiveDisplays`: Display Resources
- `indentCode`: Customizing Machine Code
- `indentScript`: Customizing Source Appearance
- `indentSource`: Customizing Source Appearance
- `initSymbols`: Finding a Place to Start
- `jdbDisplayShortcuts`: Display Shortcuts
- `jdbInitCommands`: JDB Initialization
- `jdbSettings`: JDB Initialization
- `labelDelimiter`: Customizing Buttons
- `lessTifVersion`: LessTif
- `lineBufferedConsole`: Input/Output
- `lineNumberWidth`: Customizing Source Appearance
- `linesAboveCursor`: Customizing Source Scrolling
- `linesBelowCursor`: Customizing Source Scrolling
- `listCoreCommand`: Customizing Remote Debugging
- `listDirCommand`: Customizing Remote Debugging
- `listExecCommand`: Customizing Remote Debugging
- `listSourceCommand`: Customizing Remote Debugging
- `lookup`: Images
- `maintenance`: Customizing Diagnostics
- `makeInitCommands`: GNU Make Initialization
- `maketemp`: Images
- `maxDisassemble`: Customizing Machine Code
- `maxGlyphs`: Customizing Glyphs
- `maxUndoDepth`: Customizing Undo
- `maxUndoSize`: Customizing Undo
- `new_break`: Images
- `new_display`: Images
- `new_watch`: Images
- `openDataWindow`: Toggling Windows
- `openDebuggerConsole`: Toggling Windows
- `openSelection`: Opening the Selection
- `openSourceWindow`: Toggling Windows
- `PAGER`: Customizing Diagnostics
- `PAGER`: Environment
- `pannedGraphEditor`: Scrolling Data
- `paperSize`: Printing the Graph
- `perlDisplayShortcuts`: Display Shortcuts
- `perlInitCommands`: Perl Initialization
- `perlSettings`: Perl Initialization
- `plain_arrow`: Images
- `plain_cond`: Images
- `plain_stop`: Images
- `plain_temp`: Images
- `plot2dSettings`: Gnuplot Settings
- `plot3dSettings`: Gnuplot Settings
- `plotCommand`: Gnuplot Invocation
- `plotInitCommands`: Gnuplot Settings
- `plotTermType`: Gnuplot Invocation
- `plotWindowClass`: Gnuplot Invocation
- `plotWindowDelay`: Gnuplot Invocation
- `popdownHistorySize`: Text Fields
- `positionTimeout`: Debugger Communication
- `print`: Images
- `printCommand`: Printing the Graph
- `properties`: Images
- `psCommand`: Customizing Attaching to Processes
- `pydbDisplayShortcuts`: Display Shortcuts
- `pydbInitCommands`: PYDB Initialization
- `pydbSettings`: PYDB Initialization
- `questionTimeout`: Debugger Communication
- `rotate`: Images
- `rshCommand`: Customizing Remote Debugging
- `runInterruptDelay`: Debugger Communication
- `saveHistoryOnExit`: Command History
- `saveOptionsOnExit`: Saving Options
- `selectAllBindings`: Customizing the Edit Menu
- `separateDataWindow`: Window Layout
- `separateExecWindow`: Customizing the Execution Window
- `separateSourceWindow`: Window Layout
- `set`: Images
- `SHELL`: Arguments
- `show`: Images
- `showBaseDisplayTitles`: Display Resources
- `showConfiguration`: Customizing Diagnostics
- `showDependentDisplayTitles`: Display Resources
- `showFonts`: Customizing Diagnostics
- `showInvocation`: Customizing Diagnostics
- `showLicense`: Customizing Diagnostics
- `showManual`: Customizing Diagnostics
- `showMemberNames`: Rotating Displays
- `showNews`: Customizing Diagnostics
- `showVersion`: Customizing Diagnostics
- `signal_arrow`: Images
- `sortPopdownHistory`: Text Fields
- `sourceButtons`: Customizing Buttons
- `sourceEditing`: In-Place Editing
- `sourceInitCommands`: GDB Initialization
- `splashScreen`: Splash Screen
- `splashScreenColorKey`: Splash Screen
- `startupTipCount`: Tip of the day
- `startupTips`: Tip of the day
- `statusAtBottom`: Window Layout
- `stickyTool`: Customizing Tool Position
- `stopAndContinue`: Debugger Communication
- `structOrientation`: Rotating Displays
- `suppressTheme`: Display Resources
- `suppressWarnings`: Customizing Diagnostics
- `suppressWarnings`: X Warnings
- `synchronousDebugger`: Debugger Communication
- `tabWidth`: Customizing Source Appearance
- `TERM`: Customizing the Execution Window
- `TERM`: Environment
- `TERMCAP`: Environment
- `termCommand`: Customizing the Execution Window
- `terminateOnEOF`: Debugger Communication
- `termType`: Customizing the Execution Window
- `themes`: Display Resources
- `tip`: Tip of the day
- `toolbarsAtBottom`: Window Layout
- `toolButtons`: Customizing Buttons
- `toolRightOffset`: Customizing Tool Position
- `toolTopOffset`: Customizing Tool Position
- `trace`: Customizing Diagnostics
- `typedAliases`: Shared Structures
- `uncompressCommand`: Help Helpers
- `undisplay`: Images
- `uniconifyWhenReady`: Icons
- `unwatch`: Images
- `useSourcePath`: Customizing Source Lookup
- `useTTYCommand`: Debugger Communication
- `valueDocs`: Value Tips
- `valueTips`: Value Tips
- `variableWidthFont`: Customizing Fonts
- `variableWidthFontSize`: Customizing Fonts
- `verifyButtons`: Customizing Buttons
- `vslBaseDefs`: VSL Resources
- `vslDefs`: VSL Resources
- `vslLibrary`: VSL Resources
- `vslPath`: VSL Resources
- `warnIfLocked`: Multiple Instances
- `watch`: Images
- `WWWBROWSER`: Help Helpers
- `wwwCommand`: Help Helpers
- `wwwPage`: Help Helpers
- `xdbDisplayShortcuts`: Display Shortcuts
- `xdbInitCommands`: XDB Initialization
- `xdbSettings`: XDB Initialization
- `XEDITOR`: Customizing Editing

Next: Concept Index, Previous: Resource Index, Up: Top

## File Index

- `.emacs`: Integrating <acronym>DDD</acronym>
- `.gdbinit`: Debugging <acronym>DDD</acronym>
- `.gdbinit`: Remote Program
- `.gdbinit`: GDB Options
- `ChangeLog`: Contributors
- `dbx`: Options
- `Ddd`: Application Defaults
- `Ddd`: More Customizations
- `Ddd`: Resources
- `ddd-3.3.12-html-manual.tar.gz`: About this Manual
- `ddd-3.3.12-pics.tar.gz`: About this Manual
- `ddd-3.3.12.tar.gz`: About this Manual
- `ddd-`version`-html-manual.tar.gz`: Getting <acronym>DDD</acronym>
- `ddd-`version`-pics.tar.gz`: Getting <acronym>DDD</acronym>
- `ddd-`version`.tar.gz`: Getting <acronym>DDD</acronym>
- `emacs`: Integrating <acronym>DDD</acronym>
- `emacs`: Customizing Editing
- `emacs`: Help Helpers
- `emacsclient`: Customizing Editing
- `emacsserver`: Customizing Editing
- `fig2dev`: Printing the Graph
- `file`: Customizing Remote Debugging
- `firefox`: Help Helpers
- `gdb`: Options
- `gdbserver`: Remote Program
- `gnuclient`: Customizing Editing
- `gnudoit`: Help Helpers
- `gnuplot`: Plot Appearance
- `gnuserv`: Customizing Editing
- `init`: Resources
- `java.prof`: JDB Options
- `jdb`: Options
- `ladebug`: Options
- `less`: Customizing Diagnostics
- `log`: Logging
- `log`: Entering Plotting Commands
- `log`: Options
- `lynx`: Help Helpers
- `make`: Recompiling
- `mdb`: Options
- `more`: Customizing Diagnostics
- `mozilla`: Help Helpers
- `netscape`: Help Helpers
- `on`: Customizing Remote Debugging
- `perl`: Options
- `ps`: Customizing Attaching to Processes
- `pydb`: Options
- `remsh`: Customizing Remote Debugging
- `rsh`: Customizing Remote Debugging
- `sample`: Sample Session
- `sample.c`: Sample Program
- `sample.c`: Sample Session
- `sessions`: Customizing Sessions
- `ssh`: Customizing Remote Debugging
- `stty`: Input/Output
- `suppress.vsl`: Display Resources
- `TODO`: Contributors
- `transfig`: Printing the Graph
- `vi`: Customizing Editing
- `wdb`: Options
- `xdb`: Options
- `xemacs`: Integrating <acronym>DDD</acronym>
- `xemacs`: Customizing Editing
- `xemacs`: Help Helpers
- `xfig`: Printing the Graph
- `xfontsel`: Customizing Fonts
- `xmgr`: Exporting Plot Data
- `xsm`: Resuming Sessions
- `xterm`: Customizing the Execution Window
- `xxgdb`: Integrating <acronym>DDD</acronym>
- `~`: Resources
- `~`: Options

Previous: File Index, Up: Top

## Concept Index

- Aborting execution: Program Menu
- Aborting execution: Quitting
- Ada: Summary
- Aliases, detecting: Shared Structures
- Animating plots: Animating Plots
- Arguments, displaying: Displaying Local Variables
- Arguments, of the debugged program: Arguments
- Arguments, program: Starting Program Execution
- Array slices: Array Slices
- Array, artificial: Array Slices
- Array, plotting: Plotting Arrays
- Artificial arrays: Array Slices
- Assertions and breakpoints: Breakpoint Conditions
- Assertions and watchpoints: Watchpoints
- Assignment: Assignment
- Assistance: Help and Assistance
- Auto-command: Commands with Other Debuggers
- Automatic Layout: Automatic Layout
- Balloon help: Getting Help
- Bash: Summary
- Bash, invoking DDD with: Choosing an Inferior Debugger
- Box library: History
- Breakpoint: Stopping
- Breakpoint commands: Breakpoint Commands
- Breakpoint commands, vs. conditions: Breakpoint Conditions
- Breakpoint conditions: Breakpoint Conditions
- Breakpoint ignore counts: Breakpoint Ignore Counts
- Breakpoint properties: Editing Breakpoint Properties
- Breakpoint, copying: Moving and Copying Breakpoints
- Breakpoint, deleting: Deleting Breakpoints
- Breakpoint, disabling: Disabling Breakpoints
- Breakpoint, dragging: Moving and Copying Breakpoints
- Breakpoint, editing: Editing Breakpoint Properties
- Breakpoint, enabling: Disabling Breakpoints
- Breakpoint, hardware-assisted: Hardware-Assisted Breakpoints
- Breakpoint, looking up: Looking up Breakpoints
- Breakpoint, moving: Moving and Copying Breakpoints
- Breakpoint, setting: Setting Breakpoints
- Breakpoint, temporary: Temporary Breakpoints
- Breakpoint, toggling: Tool Bar
- Breakpoints, editing: Editing all Breakpoints
- Button editor: Defining Buttons
- Button tip: Getting Help
- Button tip, turning off: Button tips
- Buttons, defining: Defining Buttons
- C: Summary
- C++: Summary
- Call stack: Stack
- Chill: Summary
- Class, opening: Opening Programs
- Clipboard: Edit Menu
- Clipboard, putting displays: Deleting Displays
- Cluster: Clustering
- Cluster, and plotting: Scalars and Composites
- Clustered display, creating: Creating Single Displays
- Command completion: Command Completion
- Command history: Command History
- Command tool: Windows
- Command, argument: GDB Argument Commands
- Command, auto: Commands with Other Debuggers
- Command, breakpoint: Breakpoint Commands
- Command, defining: Defining Commands
- Command, defining in GDB: GDB Simple Commands
- Command, defining with other debuggers: Commands with Other Debuggers
- Command, recording: GDB Simple Commands
- Command, repeating: Command History
- Command, searching: Command History
- Command, user-defined: Defining Commands
- Command-line debugger: Summary
- Compact Layout: Automatic Layout
- Completion of commands: Command Completion
- Completion of quoted strings: Command Completion
- Conditions on breakpoints: Breakpoint Conditions
- Context-sensitive help: Getting Help
- Continue, at different address: Continuing Somewhere Else
- Continue, one line: Resuming Execution
- Continue, to location: Resuming Execution
- Continue, to next line: Resuming Execution
- Continue, until function returns: Resuming Execution
- Continue, until greater line is reached: Resuming Execution
- Continuing execution: Resuming Execution
- Continuing process execution: Attaching to a Process
- Contour lines, in plots: Plot Appearance
- Contributors: Contributors
- Copying displays: Deleting Displays
- Core dump, opening: Opening Core Dumps
- Core file, in sessions: Saving Sessions
- Cutting displays: Deleting Displays
- Data Theme: Using Data Themes
- Data Window: Displaying Values
- Data window: Windows
- DBX: Summary
- DBX, invoking DDD with: Choosing an Inferior Debugger
- Debugger console: Windows
- Debugger, on remote host: Remote Debugger
- Debugging DDD: Debugging <acronym>DDD</acronym>
- Debugging flags: Patching
- Debugging optimized code: Compiling for Debugging
- Default session: Resuming Sessions
- Deferred display: Creating Single Displays
- Deferred display, in sessions: Saving Sessions
- Deleting displays: Deleting Displays
- Deleting displays: Tool Bar
- Deleting displays, undoing: Deleting Displays
- Dependent display: Creating Single Displays
- Dereferencing: Dereferencing Pointers
- Detail toggling with ‘`Show/Hide`’: Tool Bar
- Detail, hiding: Showing and Hiding Details
- Detail, showing: Showing and Hiding Details
- Directory, of the debugged program: Working Directory
- Disabled displays: Showing and Hiding Details
- Disabling displays, undoing: Showing and Hiding Details
- Display: Displaying Values
- Display Editor: Editing all Displays
- Display name: Selecting Displays
- Display position: Creating Single Displays
- Display selection: Selecting Displays
- Display title: Selecting Displays
- Display value: Selecting Displays
- Display, aligning on grid: Aligning Displays
- Display, clustered: Creating Single Displays
- Display, clustering: Clustering
- Display, copying: Deleting Displays
- Display, creating: Creating Single Displays
- Display, creating: Tool Bar
- Display, customizing: Customizing Displays
- Display, cutting: Deleting Displays
- Display, deferred: Creating Single Displays
- Display, deleting: Deleting Displays
- Display, deleting: Tool Bar
- Display, dependent: Dependent Values
- Display, dependent: Creating Single Displays
- Display, disabled: Showing and Hiding Details
- Display, frozen: Stopping X Programs
- Display, hiding details: Showing and Hiding Details
- Display, locked: Stopping X Programs
- Display, moving: Moving Displays
- Display, pasting: Deleting Displays
- Display, placement: Placement
- Display, plotting the history: Plotting Histories
- Display, refreshing: Refreshing the Data Window
- Display, rotating: Rotating Displays
- Display, rotating: Tool Bar
- Display, selecting: Selecting Displays
- Display, setting: Tool Bar
- Display, setting: Remote Host
- Display, setting when invoking DDD: X Options
- Display, showing details: Showing and Hiding Details
- Display, suppressing: Deleting Displays
- Display, toggling detail: Tool Bar
- Display, updating: Refreshing the Data Window
- Displaying values: Displaying Values
- Displaying values: Examining Data
- Displaying values with ‘`Display`’: Tool Bar
- Dumping values: Examining Data
- Edge: Dependent Values
- Edge hint: Automatic Layout
- Edge hint: Shared Structures
- Editing source code: Editing Source Code
- Emacs, integrating DDD: Integrating <acronym>DDD</acronym>
- Emergency repairs: Patching
- Environment, of the debugged program: Environment
- EPROM code debugging: Hardware-Assisted Breakpoints
- Examining memory contents: Examining Memory
- Execution position, dragging: Continuing Somewhere Else
- Execution window: Using the Execution Window
- Execution window: Windows
- Execution, “undoing”: Undoing Program Execution
- Execution, aborting: Program Menu
- Execution, aborting: Quitting
- Execution, at different address: Continuing Somewhere Else
- Execution, continuing: Resuming Execution
- Execution, interrupting: Quitting
- Execution, interrupting automatically: Debugger Communication
- Execution, one line: Resuming Execution
- Execution, to location: Resuming Execution
- Execution, to next line: Resuming Execution
- Execution, until function returns: Resuming Execution
- Execution, until greater line is reached: Resuming Execution
- Exiting: Quitting
- Extending display selection: Selecting Displays
- FIG file, printing as: Printing the Graph
- Files, opening: Opening Files
- Finding items: Tool Bar
- Fonts: Customizing Fonts
- FORTRAN: Summary
- Frame: Frames
- Frame: Stack
- Frame changes, undoing: Selecting a frame
- Frame number: Frames
- Frame pointer: Frames
- Frame, selecting: Selecting a frame
- GCC: Compiling for Debugging
- GDB: Summary
- GDB, invoking DDD with: Choosing an Inferior Debugger
- Glyph: Customizing Glyphs
- GNU Make: Summary
- GNU Make, invoking DDD with: Choosing an Inferior Debugger
- GPL: Free Software
- Grabbed pointer: Stopping X Programs
- Graph, printing: Printing the Graph
- Graph, rotating: Rotating the Graph
- Grid, aligning displays: Aligning Displays
- Grid, in plots: Plot Appearance
- Help: Help and Assistance
- Help: Getting Help
- Help, in the status line: Getting Help
- Help, on buttons: Getting Help
- Help, on commands: Getting Help
- Help, on items: Getting Help
- Help, when stuck: Getting Help
- Hiding display details: Showing and Hiding Details
- Historic mode: Undoing Program Execution
- History: History
- History, plotting: Plotting Histories
- Host, remote: Remote Host
- HTML manual: About this Manual
- IBMGL file, printing as: Printing the Graph
- Icon, invoking DDD as: X Options
- Ignore count: Breakpoint Ignore Counts
- Indent, source code: Customizing Source Appearance
- Inferior debugger: Summary
- Info manual: About this Manual
- Initial frame: Frames
- Innermost frame: Frames
- Input of the debugged program: Input/Output
- Instruction, stepping: Machine Code Execution
- Integrating DDD: Integrating <acronym>DDD</acronym>
- Interrupting DDD: Quitting
- Interrupting execution: Quitting
- Interrupting execution, automatically: Debugger Communication
- Invoking: Invoking
- Java: Summary
- JDB: Summary
- JDB, invoking DDD with: Choosing an Inferior Debugger
- Jump to different address: Continuing Somewhere Else
- Killing DDD: Quitting
- Killing the debugged program: Killing the Program
- Ladebug: Summary
- Ladebug, invoking DDD with: Choosing an Inferior Debugger
- License: License
- License: Free Software
- License, Documentation: Documentation License
- License, showing on standard output: Options
- Line numbers: Customizing Source Appearance
- Local variables, displaying: Displaying Local Variables
- Logging: Logging
- Logging, disabling: Disabling Logging
- Looking up breakpoints: Looking up Breakpoints
- Looking up items: Tool Bar
- Lookups, redoing: Looking up Previous Locations
- Lookups, undoing: Looking up Previous Locations
- Lütkehaus, Dorothea: History
- Lütkehaus, Dorothea: Contributors
- Machine code window: Windows
- Machine code, examining: Machine Code
- Machine code, executing: Machine Code Execution
- Mailing list: Help and Assistance
- Make, invoking: Recompiling
- Manual, showing on standard output: Options
- Memory, dumping contents: Examining Data
- Memory, examining: Examining Memory
- Modula-2: Summary
- Modula-3: Summary
- Mouse pointer, frozen: Stopping X Programs
- Name, display: Selecting Displays
- News, showing on standard output: Options
- NORA: History
- Optimized code, debugging: Compiling for Debugging
- Option: Invoking
- Outermost frame: Frames
- Output of the debugged program: Input/Output
- Pascal: Summary
- Pasting displays: Deleting Displays
- Patching: Patching
- PDF manual: About this Manual
- Perl: Summary
- Perl, invoking DDD with: Choosing an Inferior Debugger
- PIC file, printing as: Printing the Graph
- Pipe: Input/Output
- Placement: Placement
- Plot appearance: Plot Appearance
- Plot, animating: Animating Plots
- Plot, exporting: Exporting Plot Data
- Plot, printing: Printing Plots
- Plot, scrolling: Plot Appearance
- Plotting style: Plot Appearance
- Plotting values: Plotting Values
- Plotting values: Examining Data
- Plotting values: Tool Bar
- Pointers, dereferencing: Dereferencing Pointers
- Position, of display: Creating Single Displays
- PostScript manual: About this Manual
- PostScript, printing as: Printing the Graph
- Print, output formats: Printing Values
- Printing plots: Printing Plots
- Printing the Graph: Printing the Graph
- Printing values: Printing Values
- Printing values: Examining Data
- Printing values with ‘`Print`’: Tool Bar
- Process, attaching: Attaching to a Process
- Program arguments: Starting Program Execution
- Program counter, displaying: Machine Code Execution
- Program output, confusing: Input/Output
- Program, on remote host: Remote Program
- Program, opening: Opening Programs
- Program, patching: Patching
- PSG: History
- pydb: Summary
- PYDB, invoking DDD with: Choosing an Inferior Debugger
- Python: Summary
- Quitting: Quitting
- Quotes in commands: Command Completion
- Readline: TTY mode
- Recompiling: Recompiling
- Recording commands: GDB Simple Commands
- Redirecting I/O of the debugged program: Input/Output
- Redirecting I/O to the execution window: Using the Execution Window
- Redirection: Input/Output
- Redirection, to execution window: Using the Execution Window
- Redirection, to execution window: Debugger Communication
- Redoing commands: Undo and Redo
- Redoing lookups: Looking up Previous Locations
- Refreshing displayed values: Refreshing the Data Window
- Registers, examining: Registers
- Reloading source code: Editing Source Code
- Remote debugger: Remote Debugger
- Remote host: Remote Host
- Remote program: Remote Program
- Resource, setting when invoking DDD: X Options
- Resources: Resources
- ROM code debugging: Hardware-Assisted Breakpoints
- Rotating displays with ‘`Rotate`’: Tool Bar
- Rotating the graph: Rotating the Graph
- Running the debugged program: Running
- Scalars, plotting: Scalars and Composites
- Scales, in plots: Plot Appearance
- Scrolling: Scrolling Data
- Search, using ‘`Find >>`’: Tool Bar
- Searching commands: Command History
- Selecting frames: Selecting a frame
- Selecting multiple displays: Selecting Displays
- Selecting single displays: Selecting Displays
- Session: Sessions
- Session, active: Saving Sessions
- Session, default: Resuming Sessions
- Session, deleting: Deleting Sessions
- Session, opening: Resuming Sessions
- Session, resuming: Resuming Sessions
- Session, saving: Saving Sessions
- Session, setting when invoking DDD: Options
- Setting variables: Assignment
- Setting variables with ‘`Set`’: Tool Bar
- Shared structures, detecting: Shared Structures
- Showing display details: Showing and Hiding Details
- SIGABRT signal: Program Menu
- SIGABRT signal: Quitting
- SIGALRM signal: Signals
- SIGINT signal: Signals
- SIGINT signal: Interrupting
- Signal settings, editing: Signals
- Signal settings, saving: Signals
- Signal, fatal: Signals
- Signal, sending to DDD: Quitting
- Signals: Signals
- SIGSEGV signal: Signals
- SIGTRAP signal: Signals
- SIGUSR1 signal: Debugging <acronym>DDD</acronym>
- SIGUSR1 signal: Maintenance Menu
- Source code, editing: Editing Source Code
- Source code, recompiling: Recompiling
- Source code, reloading: Editing Source Code
- Source directory: Source Path
- Source file, opening: Opening Source Files
- Source file, typing into: Typing in the Source Window
- Source path: Source Path
- Source path, specifying: Source Path
- Source window: Windows
- Source, accessing: Source Path
- Stack Frame: Frames
- Stack frame: Stack
- Stack, moving within: Selecting a frame
- Status display: Displaying Program Status
- Status line: Getting Help
- Status line, location: Window Layout
- Suppressing values: Deleting Displays
- Tab width: Customizing Source Appearance
- TeX file, printing as: Printing the Graph
- TeXinfo manual: About this Manual
- Theme, Data: Using Data Themes
- Theme, editing: Editing Themes
- Theme, for suppressing values: Deleting Displays
- Threads: Threads
- Tic Tac Toe game: Maintenance Menu
- Tip of the day: Getting Help
- Tip of the day, turning off: Tip of the day
- Tip, on buttons: Getting Help
- Tip, value: Value Tips
- Tip, value: Examining Data
- Title, display: Selecting Displays
- Tool Bar, location: Window Layout
- Tool tip: Getting Help
- Tornado: WindRiver GDB
- TTY interface: TTY mode
- TTY mode, setting when invoking DDD: Options
- TTY settings: Input/Output
- Undo deleting displays: Deleting Displays
- Undo disabling displays: Showing and Hiding Details
- Undoing commands: Undo and Redo
- Undoing frame changes: Selecting a frame
- Undoing lookups: Looking up Previous Locations
- Undoing program execution: Undoing Program Execution
- Undoing signal handling: Signals
- Updating displayed values: Refreshing the Data Window
- User-defined command: Defining Commands
- Value tip: Value Tips
- Value tip: Examining Data
- Value, display: Selecting Displays
- Value, displaying: Displaying Values
- Value, displaying: Examining Data
- Value, dumping: Examining Data
- Value, plotting: Examining Data
- Value, plotting the history: Plotting Histories
- Value, printing: Printing Values
- Value, printing: Examining Data
- Values, displaying with ‘`Display`’: Tool Bar
- Values, plotting: Plotting Values
- Values, plotting with ‘`Plot`’: Tool Bar
- Values, printing with ‘`Print`’: Tool Bar
- Values, suppressing: Deleting Displays
- Variables, setting: Assignment
- Variables, setting with ‘`Set`’: Tool Bar
- virtual machine: JDB Options
- VM: JDB Options
- VSL: History
- Watchpoint: Watchpoints
- Watchpoint: Stopping
- Watchpoint properties: Editing Watchpoint Properties
- Watchpoint, deleting: Deleting Watchpoints
- Watchpoint, editing: Editing Watchpoint Properties
- Watchpoint, setting: Setting Watchpoints
- Watchpoint, toggling: Tool Bar
- Watchpoints, editing: Editing all Watchpoints
- WDB: WDB
- WDB, invoking DDD with: WDB
- WDB, invoking DDD with: Choosing an Inferior Debugger
- WildeBeest: WDB
- WindRiver GDB: WindRiver GDB
- Working directory, of the debugged program: Working Directory
- X programs, stopping: Stopping X Programs
- X server, frozen: Stopping X Programs
- X server, locked: Stopping X Programs
- X session: Resuming Sessions
- X Warnings, suppressing: X Warnings
- XDB: Summary
- XDB, invoking DDD with: Choosing an Inferior Debugger
- XEmacs, integrating DDD: Integrating <acronym>DDD</acronym>
- XXGDB, integrating DDD: Integrating <acronym>DDD</acronym>
- Zeller, Andreas: History
- Zeller, Andreas: Contributors

#### Footnotes

[1] Within DDD (and this manual), Ladebug is considered a DBX variant. Hence, everything said for DBX also applies to Ladebug, unless stated otherwise.

[2] XDB will no longer be maintained in future DDD releases. Use a recent GDB version instead.

[3] Actual numbers and behavior on your system may vary.

[4] Re-invoke DDD with `--gdb`, if you do not see a ‘`(gdb)`’ prompt here (see Choosing an Inferior Debugger)

[5] Only if a core file is included.

[6] If a core file is not to be included in the session, DDD data displays are saved as deferred; that is, they will be restored as soon as program execution reaches the scope in which they were created. See Creating Single Displays, for details.

[7] Requires X11R6 or later.

[8] If you use a `Ddd` application-defaults file, you will not be able to maintain multiple DDD versions at the same time. This is why the suiting `Ddd` is normally compiled into the DDD executable.

[9] If you use DDD to debug Perl, Python or Bash scripts, then this section does not apply.

[10] With XDB and some DBX variants, the debugged program must be specified upon invocation and cannot be changed at run time.

[11] JDB, `pydb`, Perl, and Bash do not support core dumps.

[12] JDB does not support breakpoint disabling.

[13] JDB does not support temporary breakpoints.

[14] GDB has no way to make a temporary breakpoint non-temporary again.

[15] JDB, Perl and some DBX variants do not support breakpoint ignore counts.

[16] JDB, `pydb`, and some DBX variants do not support breakpoint commands.

[17] When glyphs are disabled (see Customizing Source), breakpoints cannot be dragged. Delete and set breakpoints instead.

[18] Watchpoints are available in GDB and some DBX variants only. In XDB, a similar feature is available via XDB assertions; see the XDB documentation for details.

[19] If <Ctrl+C> is not bound to ‘`Copy`’ (see Customizing the Edit Menu), you can also use <Ctrl+C> to interrupt the running program.

[20] If the debuggee runs in a separate execution window, the debuggee's `TERM` value is set according to the ‘`termType`’ resource; See Customizing the Execution Window, for details.

[21] The execution window is not available in JDB.

[22] JDB, `pydb`, Perl, and Bash do not support attaching the debugger to running processes.

[23] JDB, `pydb`, Perl, and Bash do not support altering the execution position.

[24] When glyphs are disabled (see Customizing Source), dragging the execution position is not possible. Set the execution position explicitly instead.

[25] Perl does not allow changing the current stack frame.

[26] Currently, threads are supported in GDB and JDB only.

[27] This requires that the full array size is known to the debugger.

[28] JDB 1.1 does not support changing variable values.

[29] The string ‘`//`’; can be changed via the ‘`labelDelimiter`’ resource. See Customizing Buttons, for details.

[30] The machine code window is available with GDB and some DBX variants only.

[31] The machine code window is available with GDB and some DBX variants only.

[32] If you use DDD commands within command definitions, or if you include debugger commands that resume execution, these commands will be realized transparently as auto-commands—that is, they won't be executed directly by the inferior debugger, but result in a command string being sent to DDD. This command string is then interpreted by DDD and sent back to the inferior debugger, possibly prefixed by some other commands such that DDD can update its state. See Commands with Other Debuggers, for a discussion.

[33] Since the inferior debugger is invoked through a virtual TTY, standard error is normally redirected to standard output, so DDD never receives standard error from the inferior debugger.

[34] This section was contributed by Gary Cliff from Computing Devices Canada Ltd., gary.cliff@cdott.com.