Next: Enabling and Disabling Warnings, Up: Handling Warnings [Contents][Index]
It is possible to issue warnings from any code using the warning
function. In its most simple form, the warning function takes a
string describing the warning as its input argument. As an example,
the following code controls if the variable ‘a’ is non-negative,
and if not issues a warning and sets ‘a’ to zero.
a = -1;
if (a < 0)
warning ("'a' must be non-negative. Setting 'a' to zero.");
a = 0;
endif
-| 'a' must be non-negative. Setting 'a' to zero.
Since warnings aren’t fatal to a running program, it is not possible
to catch a warning using the try statement or something similar.
It is however possible to access the last warning as a string using the
lastwarn function.
It is also possible to assign an identification string to a warning.
If a warning has such an ID the user can enable and disable this warning
as will be described in the next section. To assign an ID to a warning,
simply call warning with two string arguments, where the first
is the identification string, and the second is the actual warning. Note
that warning IDs are in the format "NAMESPACE:WARNING-NAME". The
namespace "Octave" is used for Octave’s own warnings. Any other string
is available as a namespace for user’s own warnings.
Format the optional arguments under the control of the template string
template using the same rules as the printf family of
functions (see Formatted Output) and print the resulting message
on the stderr stream. The message is prefixed by the character
string ‘warning: ’.
You should use this function when you want to notify the user
of an unusual condition, but only when it makes sense for your program
to go on.
The optional message identifier allows users to enable or disable
warnings tagged by id. A message identifier is of the form
"NAMESPACE:WARNING-NAME". Octave’s own warnings use the "Octave"
namespace (see XREFwarning_ids). The special identifier "all"
may be used to set the state of all warnings.
If the first argument is "on" or "off",
set the state of a particular warning using the identifier id. If the
first argument is "query", query the state of this warning
instead. If the identifier is omitted, a value of "all" is
assumed. If you set the state of a warning to "error", the
warning named by id is handled as if it were an error instead. So,
for example, the following handles all warnings as errors:
warning ("error");
If the state is "on", "off", or "error"
and the third argument is "local", then the warning state
will be set temporarily, until the end of the current function.
Changes to warning states that are set locally affect the current
function and all functions called from the current scope. The
previous warning state is restored on return from the current
function. The "local" option is ignored if used in the top-level
workspace.
Implementation Note: For compatibility with MATLAB, escape
sequences (e.g., "\n" => newline) are processed in template
regardless of whether template has been defined within single quotes
as long as there are two or more input arguments.
Use a second backslash to stop interpolation of the escape sequence (e.g.,
"\\n") or use the regexptranslate function.
See also: warning_ids, lastwarn, error.
Query or set the last warning message. When called without input arguments, return the last warning message and message identifier. With one argument, set the last warning message to msg. With two arguments, also set the last message identifier.
The functions distributed with Octave can issue one of the following warnings.
Octave:abbreviated-property-matchBy default, the Octave:abbreviated-property-match warning is enabled.
Octave:array-to-scalarIf the Octave:array-to-scalar warning is enabled, Octave will
warn when an implicit conversion from an array to a scalar value is
attempted.
By default, the Octave:array-to-scalar warning is disabled.
Octave:array-to-vectorIf the Octave:array-to-vector warning is enabled, Octave will
warn when an implicit conversion from an array to a vector value is
attempted.
By default, the Octave:array-to-vector warning is disabled.
Octave:assign-as-truth-valueIf the Octave:assign-as-truth-value warning is
enabled, a warning is issued for statements like
if (s = t) …
since such statements are not common, and it is likely that the intent was to write
if (s == t) …
instead.
There are times when it is useful to write code that contains
assignments within the condition of a while or if
statement. For example, statements like
while (c = getc ()) …
are common in C programming.
It is possible to avoid all warnings about such statements by
disabling the Octave:assign-as-truth-value warning,
but that may also let real errors like
if (x = 1) # intended to test (x == 1)! …
slip by.
In such cases, it is possible suppress errors for specific statements by writing them with an extra set of parentheses. For example, writing the previous example as
while ((c = getc ())) …
will prevent the warning from being printed for this statement, while allowing Octave to warn about other assignments used in conditional contexts.
By default, the Octave:assign-as-truth-value warning is enabled.
Octave:associativity-changeIf the Octave:associativity-change warning is
enabled, Octave will warn about possible changes in the meaning of
some code due to changes in associativity for some operators.
Associativity changes have typically been made for MATLAB
compatibility.
By default, the Octave:associativity-change warning is enabled.
Octave:autoload-relative-file-nameIf the Octave:autoload-relative-file-name is enabled,
Octave will warn when parsing autoload() function calls with relative
paths to function files. This usually happens when using autoload()
calls in PKG_ADD files, when the PKG_ADD file is not in the same
directory as the .oct file referred to by the autoload() command.
By default, the Octave:autoload-relative-file-name warning is enabled.
Octave:broadcastWarn when performing broadcasting operations. By default, this is enabled. See Broadcasting in the chapter Vectorization and Faster Code Execution of the manual.
Octave:built-in-variable-assignmentBy default, the Octave:built-in-variable-assignment warning is
enabled.
Octave:deprecated-keywordIf the Octave:deprecated-keyword warning is enabled, a
warning is issued when Octave encounters a keyword that is obsolete and
scheduled for removal from Octave.
By default, the Octave:deprecated-keyword warning is enabled.
Octave:divide-by-zeroIf the Octave:divide-by-zero warning is enabled, a
warning is issued when Octave encounters a division by zero.
By default, the Octave:divide-by-zero warning is enabled.
Octave:fopen-file-in-pathBy default, the Octave:fopen-file-in-path warning is enabled.
Octave:function-name-clashIf the Octave:function-name-clash warning is enabled, a
warning is issued when Octave finds that the name of a function
defined in a function file differs from the name of the file. (If
the names disagree, the name declared inside the file is ignored.)
By default, the Octave:function-name-clash warning is enabled.
Octave:future-time-stampIf the Octave:future-time-stamp warning is enabled, Octave
will print a warning if it finds a function file with a time stamp
that is in the future.
By default, the Octave:future-time-stamp warning is enabled.
Octave:glyph-renderBy default, the Octave:glyph-render warning is enabled.
Octave:imag-to-realIf the Octave:imag-to-real warning is enabled, a warning is
printed for implicit conversions of complex numbers to real numbers.
By default, the Octave:imag-to-real warning is disabled.
Octave:load-file-in-pathBy default, the Octave:load-file-in-path warning is enabled.
Octave:logical-conversionBy default, the Octave:logical-conversion warning is enabled.
Octave:matlab-incompatiblePrint warnings for Octave language features that may cause
compatibility problems with MATLAB.
By default, the Octave:matlab-incompatible warning is disabled.
The –traditional or –braindead startup options for Octave may also
be of use, see Command Line Options.
Octave:md5sum-file-in-pathBy default, the Octave:md5sum-file-in-path warning is enabled.
Octave:missing-glyphBy default, the Octave:missing-glyph warning is enabled.
Octave:missing-semicolonIf the Octave:missing-semicolon warning is enabled, Octave
will warn when statements in function definitions don’t end in
semicolons.
By default the Octave:missing-semicolon warning is disabled.
Octave:mixed-string-concatIf the Octave:mixed-string-concat warning is enabled, print a
warning when concatenating a mixture of double and single quoted strings.
By default, the Octave:mixed-string-concat warning is disabled.
Octave:neg-dim-as-zeroIf the Octave:neg-dim-as-zero warning is enabled, print a warning
for expressions like
eye (-1)
By default, the Octave:neg-dim-as-zero warning is disabled.
Octave:nested-functions-coercedBy default, the Octave:nested-functions-coerced warning is enabled.
Octave:noninteger-range-as-indexBy default, the Octave:noninteger-range-as-index warning is enabled.
Octave:num-to-strIf the Octave:num-to-str warning is enable, a warning is
printed for implicit conversions of numbers to their ASCII character
equivalents when strings are constructed using a mixture of strings and
numbers in matrix notation. For example,
[ "f", 111, 111 ] ⇒ "foo"
elicits a warning if the Octave:num-to-str warning is
enabled. By default, the Octave:num-to-str warning is enabled.
Octave:possible-matlab-short-circuit-operatorIf the Octave:possible-matlab-short-circuit-operator warning
is enabled, Octave will warn about using the not short circuiting
operators & and | inside if or while
conditions. They normally never short circuit, but MATLAB always
short circuits if any logical operators are used in a condition. You
can turn on the option
do_braindead_shortcircuit_evaluation (1)
if you would like to enable this short-circuit evaluation in
Octave. Note that the && and || operators always short
circuit in both Octave and MATLAB, so it’s only necessary to
enable MATLAB-style short-circuiting if it’s too arduous to modify
existing code that relies on this behavior.
By default, the Octave:possible-matlab-short-circuit-operator warning
is enabled.
Octave:precedence-changeIf the Octave:precedence-change warning is enabled, Octave
will warn about possible changes in the meaning of some code due to
changes in precedence for some operators. Precedence changes have
typically been made for MATLAB compatibility.
By default, the Octave:precedence-change warning is enabled.
Octave:recursive-path-searchBy default, the Octave:recursive-path-search warning is enabled.
Octave:remove-init-dirThe path function changes the search path that Octave uses
to find functions. It is possible to set the path to a value which
excludes Octave’s own built-in functions. If the
Octave:remove-init-dir warning is enabled then Octave will warn
when the path function has been used in a way that may render
Octave unworkable.
By default, the Octave:remove-init-dir warning is enabled.
Octave:reload-forces-clearIf several functions have been loaded from the same file, Octave must
clear all the functions before any one of them can be reloaded. If
the Octave:reload-forces-clear warning is enabled, Octave will
warn you when this happens, and print a list of the additional
functions that it is forced to clear.
By default, the Octave:reload-forces-clear warning is enabled.
Octave:resize-on-range-errorIf the Octave:resize-on-range-error warning is enabled, print a
warning when a matrix is resized by an indexed assignment with
indices outside the current bounds.
By default, the ## Octave:resize-on-range-error warning is disabled.
Octave:separator-insertPrint warning if commas or semicolons might be inserted
automatically in literal matrices.
By default, the Octave:separator-insert warning is disabled.
Octave:shadowed-functionBy default, the Octave:shadowed-function warning is enabled.
Octave:single-quote-stringPrint warning if a single quote character is used to introduce a
string constant.
By default, the Octave:single-quote-string warning is disabled.
Octave:singular-matrix-divBy default, the Octave:singular-matrix-div warning is enabled.
Octave:sqrtm:SingularMatrixBy default, the Octave:sqrtm:SingularMatrix warning is enabled.
Octave:str-to-numIf the Octave:str-to-num warning is enabled, a warning is printed
for implicit conversions of strings to their numeric ASCII equivalents.
For example,
"abc" + 0 ⇒ 97 98 99
elicits a warning if the Octave:str-to-num warning is enabled.
By default, the Octave:str-to-num warning is disabled.
Octave:undefined-return-valuesIf the Octave:undefined-return-values warning is disabled,
print a warning if a function does not define all the values in
the return list which are expected.
By default, the Octave:undefined-return-values warning is enabled.
Octave:variable-switch-labelIf the Octave:variable-switch-label warning is enabled, Octave
will print a warning if a switch label is not a constant or constant
expression.
By default, the Octave:variable-switch-label warning is disabled.
Next: Enabling and Disabling Warnings, Up: Handling Warnings [Contents][Index]