Keywords: ISO C++, test, testsuite, performance, conformance, ABI, exception safety

Test
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## Test

The libstdc++ testsuite includes testing for standard conformance, regressions, ABI, and performance.

### Organization

#### Directory Layout

The directory libsrcdir/testsuite contains the individual test cases organized in sub-directories corresponding to chapters of the C++ standard (detailed below), the dejagnu test harness support files, and sources to various testsuite utilities that are packaged in a separate testing library.

All test cases for functionality required by the runtime components of the C++ standard (ISO 14882) are files within the following directories.

    17_intro
    18_support
    19_diagnostics
    20_util
    21_strings
    22_locale
    23_containers
    25_algorithms
    26_numerics
    27_io
    28_regex
    29_atomics
    30_threads

In addition, the following directories include test files:

    tr1		  Tests for components as described by the Technical Report on Standard Library Extensions (TR1).
    backward	  Tests for backwards compatibility and deprecated features.
    demangle	  Tests for __cxa_demangle, the IA 64 C++ ABI demangler
    ext		  Tests for extensions.
    performance	  Tests for performance analysis, and performance regressions.

Some directories don't have test files, but instead contain auxiliary information:

    config		  Files for the dejagnu test harness.
    lib		  Files for the dejagnu test harness.
    libstdc++*     	  Files for the dejagnu test harness.
    data		  Sample text files for testing input and output.
    util		  Files for libtestc++, utilities and testing routines.

Within a directory that includes test files, there may be additional subdirectories, or files. Originally, test cases were appended to one file that represented a particular section of the chapter under test, and was named accordingly. For instance, to test items related to `21.3.6.1 - basic_string::find [lib.string::find]` in the standard, the following was used:

    21_strings/find.cc

However, that practice soon became a liability as the test cases became huge and unwieldy, and testing new or extended functionality (like wide characters or named locales) became frustrating, leading to aggressive pruning of test cases on some platforms that covered up implementation errors. Now, the test suite has a policy of one file, one test case, which solves the above issues and gives finer grained results and more manageable error debugging. As an example, the test case quoted above becomes:

    21_strings/basic_string/find/char/1.cc
    21_strings/basic_string/find/char/2.cc
    21_strings/basic_string/find/char/3.cc
    21_strings/basic_string/find/wchar_t/1.cc
    21_strings/basic_string/find/wchar_t/2.cc
    21_strings/basic_string/find/wchar_t/3.cc

All new tests should be written with the policy of one test case, one file in mind.

#### Naming Conventions

In addition, there are some special names and suffixes that are used within the testsuite to designate particular kinds of tests.

- _xin.cc

  This test case expects some kind of interactive input in order to finish or pass. At the moment, the interactive tests are not run by default. Instead, they are run by hand, like:

      g++ 27_io/objects/char/3_xin.cc
      cat 27_io/objects/char/3_xin.in | a.out

- .in

  This file contains the expected input for the corresponding _xin.cc test case.

- _neg.cc

  This test case is expected to fail: it's a negative test. At the moment, these are almost always compile time errors.

- char

  This can either be a directory name or part of a longer file name, and indicates that this file, or the files within this directory are testing the `char` instantiation of a template.

- wchar_t

  This can either be a directory name or part of a longer file name, and indicates that this file, or the files within this directory are testing the `wchar_t` instantiation of a template. Some hosts do not support `wchar_t` functionality, so for these targets, all of these tests will not be run.

- thread

  This can either be a directory name or part of a longer file name, and indicates that this file, or the files within this directory are testing situations where multiple threads are being used.

- performance

  This can either be an enclosing directory name or part of a specific file name. This indicates a test that is used to analyze runtime performance, for performance regression testing, or for other optimization related analysis. At the moment, these test cases are not run by default.

### Running the Testsuite

#### Basic

You can check the status of the build without installing it using the dejagnu harness, much like the rest of the gcc tools.

     make check

in the libbuilddir directory.

or

     make check-target-libstdc++-v3

in the gccbuilddir directory.

These commands are functionally equivalent and will create a 'testsuite' directory underneath libbuilddir containing the results of the tests. Two results files will be generated: libstdc++.sum, which is a PASS/FAIL summary for each test, and libstdc++.log which is a log of the exact command line passed to the compiler, the compiler output, and the executable output (if any).

Archives of test results for various versions and platforms are available on the GCC website in the build status section of each individual release, and are also archived on a daily basis on the gcc-testresults mailing list. Please check either of these places for a similar combination of source version, operating system, and host CPU.

#### Variations

There are several options for running tests, including testing the regression tests, testing a subset of the regression tests, testing the performance tests, testing just compilation, testing installed tools, etc. In addition, there is a special rule for checking the exported symbols of the shared library.

To debug the dejagnu test harness during runs, try invoking with a specific argument to the variable RUNTESTFLAGS, as below.

    make check-target-libstdc++-v3 RUNTESTFLAGS="-v"

or

    make check-target-libstdc++-v3 RUNTESTFLAGS="-v -v"

To run a subset of the library tests, you will need to generate the testsuite_files file by running make testsuite_files in the libbuilddir/testsuite directory, described below. Edit the file to remove the tests you don't want and then run the testsuite as normal.

There are two ways to run on a simulator: set up DEJAGNU to point to a specially crafted site.exp, or pass down --target_board flags.

Example flags to pass down for various embedded builds are as follows:

          --target=powerpc-eabism (libgloss/sim)
    make check-target-libstdc++-v3 RUNTESTFLAGS="--target_board=powerpc-sim"

    --target=calmrisc32 (libgloss/sid)
    make check-target-libstdc++-v3 RUNTESTFLAGS="--target_board=calmrisc32-sid"

    --target=xscale-elf (newlib/sim)
    make check-target-libstdc++-v3 RUNTESTFLAGS="--target_board=arm-sim"

Also, here is an example of how to run the libstdc++ testsuite for a multilibed build directory with different ABI settings:

    make check-target-libstdc++-v3 RUNTESTFLAGS='--target_board \"unix{-mabi=32,,-mabi=64}\"'

You can run the tests with a compiler and library that have already been installed. Make sure that the compiler (e.g., `g++`) is in your `PATH`. If you are using shared libraries, then you must also ensure that the directory containing the shared version of libstdc++ is in your `LD_LIBRARY_PATH`, or equivalent. If your GCC source tree is at `/path/to/gcc`, then you can run the tests as follows:

    runtest --tool libstdc++ --srcdir=/path/to/gcc/libstdc++-v3/testsuite

The testsuite will create a number of files in the directory in which you run this command,. Some of those files might use the same name as files created by other testsuites (like the ones for GCC and G++), so you should not try to run all the testsuites in parallel from the same directory.

In addition, there are some testing options that are mostly of interest to library maintainers and system integrators. As such, these tests may not work on all cpu and host combinations, and may need to be executed in the libbuilddir/testsuite directory. These options include, but are not necessarily limited to, the following:

       make testsuite_files

Five files are generated that determine what test files are run. These files are:

- testsuite_files

  This is a list of all the test cases that will be run. Each test case is on a separate line, given with an absolute path from the libsrcdir/testsuite directory.

- testsuite_files_interactive

  This is a list of all the interactive test cases, using the same format as the file list above. These tests are not run by default.

- testsuite_files_performance

  This is a list of all the performance test cases, using the same format as the file list above. These tests are not run by default.

- testsuite_thread

  This file indicates that the host system can run tests which involved multiple threads.

- testsuite_wchar_t

  This file indicates that the host system can run the wchar_t tests, and corresponds to the macro definition `_GLIBCXX_USE_WCHAR_T` in the file c++config.h.

       make check-abi

The library ABI can be tested. This involves testing the shared library against an ABI-defining previous version of symbol exports.

       make check-compile

This rule compiles, but does not link or execute, the testsuite_files test cases and displays the output on stdout.

       make check-performance

This rule runs through the testsuite_files_performance test cases and collects information for performance analysis and can be used to spot performance regressions. Various timing information is collected, as well as number of hard page faults, and memory used. This is not run by default, and the implementation is in flux.

We are interested in any strange failures of the testsuite; please email the main libstdc++ mailing list if you see something odd or have questions.

#### Permutations

To run the libstdc++ test suite under the debug mode, edit `libstdc++-v3/scripts/testsuite_flags` to add the compile-time flag `-D_GLIBCXX_DEBUG` to the result printed by the `--build-cxx` option. Additionally, add the `-D_GLIBCXX_DEBUG_PEDANTIC` flag to turn on pedantic checking. The libstdc++ test suite should produce precisely the same results under debug mode that it does under release mode: any deviation indicates an error in either the library or the test suite.

The parallel mode can be tested in much the same manner, substituting `-D_GLIBCXX_PARALLEL` for `-D_GLIBCXX_DEBUG` in the previous paragraph.

Or, just run the testsuites with `CXXFLAGS` set to `-D_GLIBCXX_DEBUG` or `-D_GLIBCXX_PARALLEL`.

### Writing a new test case

The first step in making a new test case is to choose the correct directory and file name, given the organization as previously described.

All files are copyright the FSF, and GPL'd: this is very important. The first copyright year should correspond to the date the file was checked in to SVN.

As per the dejagnu instructions, always return 0 from main to indicate success.

A bunch of utility functions and classes have already been abstracted out into the testsuite utility library, `libtestc++`. To use this functionality, just include the appropriate header file: the library or specific object files will automatically be linked in as part of the testsuite run.

For a test that needs to take advantage of the dejagnu test harness, what follows below is a list of special keyword that harness uses. Basically, a test case contains dg-keywords (see dg.exp) indicating what to do and what kinds of behavior are to be expected. New test cases should be written with the new style DejaGnu framework in mind.

To ease transition, here is the list of dg-keyword documentation lifted from dg.exp.

    # The currently supported options are:
    #
    # dg-prms-id N
    #	set prms_id to N
    #
    # dg-options "options ..." [{ target selector }]
    #	specify special options to pass to the tool (eg: compiler)
    #
    # dg-do do-what-keyword [{ target/xfail selector }]
    #	`do-what-keyword' is tool specific and is passed unchanged to
    #	${tool}-dg-test.  An example is gcc where `keyword' can be any of:
    #	preprocess|compile|assemble|link|run
    #	and will do one of: produce a .i, produce a .s, produce a .o,
    #	produce an a.out, or produce an a.out and run it (the default is
    #	compile).
    #
    # dg-error regexp comment [{ target/xfail selector } [{.|0|linenum}]]
    #	indicate an error message <regexp> is expected on this line
    #	(the test fails if it doesn't occur)
    #	Linenum=0 for general tool messages (eg: -V arg missing).
    #	"." means the current line.
    #
    # dg-warning regexp comment [{ target/xfail selector } [{.|0|linenum}]]
    #	indicate a warning message <regexp> is expected on this line
    #	(the test fails if it doesn't occur)
    #
    # dg-bogus regexp comment [{ target/xfail selector } [{.|0|linenum}]]
    #	indicate a bogus error message <regexp> use to occur here
    #	(the test fails if it does occur)
    #
    # dg-build regexp comment [{ target/xfail selector }]
    #	indicate the build use to fail for some reason
    #	(errors covered here include bad assembler generated, tool crashes,
    #	and link failures)
    #	(the test fails if it does occur)
    #
    # dg-excess-errors comment [{ target/xfail selector }]
    #	indicate excess errors are expected (any line)
    #	(this should only be used sparingly and temporarily)
    #
    # dg-output regexp [{ target selector }]
    #	indicate the expected output of the program is <regexp>
    #	(there may be multiple occurrences of this, they are concatenated)
    #
    # dg-final { tcl code }
    #	add some tcl code to be run at the end
    #	(there may be multiple occurrences of this, they are concatenated)
    #	(unbalanced braces must be \-escaped)
    #
    # "{ target selector }" is a list of expressions that determine whether the
    # test succeeds or fails for a particular target, or in some cases whether the
    # option applies for a particular target.  If the case of `dg-do' it specifies
    # whether the test case is even attempted on the specified target.
    #
    # The target selector is always optional.  The format is one of:
    #
    # { xfail *-*-* ... } - the test is expected to fail for the given targets
    # { target *-*-* ... } - the option only applies to the given targets
    #
    # At least one target must be specified, use *-*-* for "all targets".
    # At present it is not possible to specify both `xfail' and `target'.
    # "native" may be used in place of "*-*-*".

    Example 1: Testing compilation only
    // { dg-do compile }

    Example 2: Testing for expected warnings on line 36, which all targets fail
    // { dg-warning "string literals" "" { xfail *-*-* } 36 }

    Example 3: Testing for expected warnings on line 36
    // { dg-warning "string literals" "" { target *-*-* } 36 }

    Example 4: Testing for compilation errors on line 41
    // { dg-do compile }
    // { dg-error "no match for" "" { target *-*-* } 41 }

    Example 5: Testing with special command line settings, or without the
    use of pre-compiled headers, in particular the stdc++.h.gch file. Any
    options here will override the DEFAULT_CXXFLAGS and PCH_CXXFLAGS set
    up in the normal.exp file.
    // { dg-options "-O0" { target *-*-* } }

More examples can be found in the libstdc++-v3/testsuite/*/*.cc files.

### Test Harness and Utilities

#### Dejagnu Harness Details

Underlying details of testing for conformance and regressions are abstracted via the GNU Dejagnu package. This is similar to the rest of GCC.

This is information for those looking at making changes to the testsuite structure, and/or needing to trace dejagnu's actions with --verbose. This will not be useful to people who are "merely" adding new tests to the existing structure.

The first key point when working with dejagnu is the idea of a "tool". Files, directories, and functions are all implicitly used when they are named after the tool in use. Here, the tool will always be "libstdc++".

The `lib` subdir contains support routines. The `lib/libstdc++.exp` file ("support library") is loaded automagically, and must explicitly load the others. For example, files can be copied from the core compiler's support directory into `lib`.

Some routines in `lib/libstdc++.exp` are callbacks, some are our own. Callbacks must be prefixed with the name of the tool. To easily distinguish the others, by convention our own routines are named "v3-*".

The next key point when working with dejagnu is "test files". Any directory whose name starts with the tool name will be searched for test files. (We have only one.) In those directories, any `.exp` file is considered a test file, and will be run in turn. Our main test file is called `normal.exp`; it runs all the tests in testsuite_files using the callbacks loaded from the support library.

The `config` directory is searched for any particular "target board" information unique to this library. This is currently unused and sets only default variables.

#### Utilities

The testsuite directory also contains some files that implement functionality that is intended to make writing test cases easier, or to avoid duplication, or to provide error checking in a way that is consistent across platforms and test harnesses. A stand-alone executable, called abi_check, and a static library called libtestc++ are constructed. Both of these items are not installed, and only used during testing.

These files include the following functionality:

- testsuite_abi.h, testsuite_abi.cc, testsuite_abi_check.cc

  Creates the executable abi_check. Used to check correctness of symbol versioning, visibility of exported symbols, and compatibility on symbols in the shared library, for hosts that support this feature. More information can be found in the ABI documentation here

- testsuite_allocator.h, testsuite_allocator.cc

  Contains specialized allocators that keep track of construction and destruction. Also, support for overriding global new and delete operators, including verification that new and delete are called during execution, and that allocation over max_size fails.

- testsuite_character.h

  Contains `std::char_traits` and `std::codecvt` specializations for a user-defined POD.

- testsuite_hooks.h, testsuite_hooks.cc

  A large number of utilities, including:

  - VERIFY

  - set_memory_limits

  - verify_demangle

  - run_tests_wrapped_locale

  - run_tests_wrapped_env

  - try_named_locale

  - try_mkfifo

  - func_callback

  - counter

  - copy_tracker

  - copy_constructor

  - assignment_operator

  - destructor

  - pod_char, pod_int and associated char_traits specializations

- testsuite_io.h

  Error, exception, and constraint checking for `std::streambuf, std::basic_stringbuf, std::basic_filebuf`.

- testsuite_iterators.h

  Wrappers for various iterators.

- testsuite_performance.h

  A number of class abstractions for performance counters, and reporting functions including:

  - time_counter

  - resource_counter

  - report_performance

### Special Topics

#### Qualifying Exception Safety Guarantees

##### Overview

Testing is composed of running a particular test sequence, and looking at what happens to the surrounding code when exceptions are thrown. Each test is composed of measuring initial state, executing a particular sequence of code under some instrumented conditions, measuring a final state, and then examining the differences between the two states.

Test sequences are composed of constructed code sequences that exercise a particular function or member function, and either confirm no exceptions were generated, or confirm the consistency/coherency of the test subject in the event of a thrown exception.

Random code paths can be constructed using the basic test sequences and instrumentation as above, only combined in a random or pseudo-random way.

To compute the code paths that throw, test instruments are used that throw on allocation events (`__gnu_cxx::throw_allocator_random` and `__gnu_cxx::throw_allocator_limit`) and copy, assignment, comparison, increment, swap, and various operators (`__gnu_cxx::throw_type_random` and `__gnu_cxx::throw_type_limit`). Looping through a given test sequence and conditionally throwing in all instrumented places. Then, when the test sequence completes without an exception being thrown, assume all potential error paths have been exercised in a sequential manner.

##### Existing tests

- Ad Hoc

  For example, `testsuite/23_containers/list/modifiers/3.cc`.

- Policy Based Data Structures

  For example, take the test functor `rand_reg_test` in in `testsuite/ext/pb_ds/regression/tree_no_data_map_rand.cc`. This uses `container_rand_regression_test` in `testsuite/util/regression/rand/assoc/container_rand_regression_test.h`.

  Which has several tests for container member functions, Includes control and test container objects. Configuration includes random seed, iterations, number of distinct values, and the probability that an exception will be thrown. Assumes instantiating container uses an extension allocator, `__gnu_cxx::throw_allocator_random`, as the allocator type.

- C++11 Container Requirements.

  Coverage is currently limited to testing container requirements for exception safety, although `__gnu_cxx::throw_type` meets the additional type requirements for testing numeric data structures and instantiating algorithms.

  Of particular interest is extending testing to algorithms and then to parallel algorithms. Also io and locales.

  The test instrumentation should also be extended to add instrumentation to `iterator` and `const_iterator` types that throw conditionally on iterator operations.

##### C++11 Requirements Test Sequence Descriptions

- Basic

  Basic consistency on exception propagation tests. For each container, an object of that container is constructed, a specific member function is exercised in a `try` block, and then any thrown exceptions lead to error checking in the appropriate `catch` block. The container's use of resources is compared to the container's use prior to the test block. Resource monitoring is limited to allocations made through the container's allocator_type, which should be sufficient for container data structures. Included in these tests are member functions are iterator and const_iterator operations, `pop_front`, `pop_back`, `push_front`, `push_back`, `insert`, `erase`, `swap`, `clear`, and `rehash`. The container in question is instantiated with two instrumented template arguments, with `__gnu_cxx::throw_allocator_limit` as the allocator type, and with `__gnu_cxx::throw_type_limit` as the value type. This allows the test to loop through conditional throw points.

  The general form is demonstrated in `testsuite/23_containers/list/requirements/exception/basic.cc` . The instantiating test object is `__gnu_test::basic_safety` and is detailed in `testsuite/util/exception/safety.h`.

- Generation Prohibited

  Exception generation tests. For each container, an object of that container is constructed and all member functions required to not throw exceptions are exercised. Included in these tests are member functions are iterator and const_iterator operations, `erase`, `pop_front`, `pop_back`, `swap`, and `clear`. The container in question is instantiated with two instrumented template arguments, with `__gnu_cxx::throw_allocator_random` as the allocator type, and with `__gnu_cxx::throw_type_random` as the value type. This test does not loop, an instead is sudden death: first error fails.

  The general form is demonstrated in `testsuite/23_containers/list/requirements/exception/generation_prohibited.cc` . The instantiating test object is `__gnu_test::generation_prohibited` and is detailed in `testsuite/util/exception/safety.h`.

- Propagation Consistent

  Container rollback on exception propagation tests. For each container, an object of that container is constructed, a specific member function that requires rollback to a previous known good state is exercised in a `try` block, and then any thrown exceptions lead to error checking in the appropriate `catch` block. The container is compared to the container's last known good state using such parameters as size, contents, and iterator references. Included in these tests are member functions are `push_front`, `push_back`, `insert`, and `rehash`. The container in question is instantiated with two instrumented template arguments, with `__gnu_cxx::throw_allocator_limit` as the allocator type, and with `__gnu_cxx::throw_type_limit` as the value type. This allows the test to loop through conditional throw points.

  The general form demonstrated in `testsuite/23_containers/list/requirements/exception/propagation_coherent.cc` . The instantiating test object is `__gnu_test::propagation_coherent` and is detailed in `testsuite/util/exception/safety.h`.

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