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.
Display a warning message or control the behavior of Octave’s warning system.
The first call form uses a template template and optional additional
arguments to display a message on the stderr stream. The message is
formatted using the same rules as the printf family of functions
(see Formatted Output) and 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. For example:
warning ("foo: maybe something wrong here");
If the warning message does not end with a newline character, Octave will
print a traceback of all the function calls leading to the warning. If the
warning message does end in a newline character, Octave will suppress the
traceback messages as it returns control to the top level. For more details
and examples, see error.
The optional warning identifier id allows users to enable or disable
warnings tagged by this identifier. A message identifier is a string of the
form "NAMESPACE:WARNING-NAME". Octave’s own warnings use the
"Octave" namespace (see warning_ids). For
example:
warning ("MyNameSpace:check-something",
"foo: maybe something wrong here");
The second call form is meant to change and/or query the state of warnings.
The first input argument must be a string state ("on",
"off", "error", or "query") followed by an optional
warning identifier id or "all" (default).
The optional output argument warning_struct is a structure or structure
array with fields "state" and "identifier". The state
argument may have the following values:
"on"|"off":Enable or disable the display of warnings identified by id and optionally return their previous state stout.
"error":Turn warnings identified by id into errors and optionally return their previous state stout.
"query":Return the current state of warnings identified by id.
A structure or structure array warning_struct, with fields
"state" and "identifier", may be given as an input to achieve
equivalent results. The following example shows how to temporarily disable a
warning and then restore its original state:
loglog (-1:10);
## Disable the previous warning and save its original state
[~, id] = lastwarn ();
warnstate = warning ("off", id);
loglog (-1:10);
## Restore its original state
warning (warnstate);
If a final argument "local" is provided 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.
With no input argument warning () is equivalent to
warning ("query", "all") except that in the absence of an output
argument, the state of warnings is displayed on stderr.
The level of verbosity of the warning system may also be controlled by two modes mode:
"backtrace":enable/disable the display of the stack trace after the warning message
"verbose":enable/disable the display of additional information after the warning message
In this case the state argument may only be "on" or
"off".
Implementation Note: For compatibility with MATLAB, escape sequences in
template (e.g., "\n" => newline) are processed
regardless of whether template has been defined with single quotes, as
long as there are two or more input arguments. To disable escape sequence
expansion use a second backslash before the 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-matchIf the Octave:abbreviated-property-match warning is enabled, a
warning is printed if a non-exact or ambiguous match is being used for a
operation specifying an object property. For example, for a graphics
object, fig, with the property 'displayname',
get (fig, 'dis') elicits a warning if the
Octave:abbreviated-property-match warning is enabled.
By default, the Octave:abbreviated-property-match warning is enabled.
Octave:addpath-pkgIf the Octave:addpath-pkg warning is enabled,
Octave will warn when a package directory (i.e., +package_name) is added
to the path. Typically, only the parent directory which contains the
package directory should be added to the load path.
By default, the Octave:addpath-pkg warning is enabled.
Octave:array-as-logicalIf the Octave:array-as-logical warning is enabled,
Octave will warn when an array of size greater than 1x1 is used
as a truth value in an if, while, or until statement.
By default, the Octave:array-as-logical warning is disabled.
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: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:charmat-truncatedIf the Octave:charmat-truncated warning is enabled, a warning is
printed when a character matrix with multiple rows is converted to a string.
In this case, the Octave interpreter keeps only the first row and discards
the others.
By default, the Octave:charmat-truncated warning is enabled.
Octave:classdef-to-structIf the Octave:classdef-to-struct warning is enabled, a warning
is issued when a classdef object is forcibly converted into a struct with
struct (CLASSDEF_OBJ). Conversion removes the access
restrictions from the object and makes private and protected properties
visible.
By default, the Octave:classdef-to-struct warning is enabled.
Octave:colon-complex-argumentIf the Octave:colon-complex-argument warning is enabled, a warning
is issued when one of the three arguments to the colon operator (base,
increment, limit) is a complex value. For example, 1:3*i will
cause a warning to be emitted.
By default, the Octave:colon-complex-argument warning is enabled.
Octave:colon-nonscalar-argumentIf the Octave:colon-nonscalar-argument warning is enabled, a warning
is issued when one of the three arguments to the colon operator (base,
increment, limit) is not a scalar. For example, 1:[3, 5] will
cause a warning to be emitted.
By default, the Octave:colon-nonscalar-argument warning is enabled.
Octave:data-file-in-pathIf the Octave:data-file-in-path warning is enabled, a warning is
issued when Octave does not find the target of a file operation such as
load or fopen directly, but is able to locate the file in
Octave’s search path for files. The warning could indicate that a
different file target than the programmer intended is being used.
By default, the Octave:data-file-in-path warning is enabled.
Octave:deprecated-functionIf the Octave:deprecated-function warning is enabled, a
warning is issued when Octave encounters a function that is obsolete and
scheduled for removal from Octave.
By default, the Octave:deprecated-function 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:deprecated-propertyIf the Octave:deprecated-property warning is enabled, a
warning is issued when Octave encounters a graphics property that
is obsolete and scheduled for removal from Octave.
By default, the Octave:deprecated-property warning is enabled.
Octave:eigs:UnconvergedEigenvaluesIf the Octave:eigs:UnconvergedEigenvalues warning is enabled then
the eigs function will issue a warning if the number of calculated
eigenvalues is less than the number of requested eigenvalues.
By default, the Octave:eigs:UnconvergedEigenvalues warning is
enabled.
Octave:empty-indexIf the Octave:empty-index warning is enabled then Octave will emit a
warning whenever indexing operators are used without an index, for example
x().
By default, the Octave:empty-index warning is enabled.
Octave:erase:chararrayIf the Octave:erase:chararray warning is enabled then the erase
function will issue a warning if the input pattern is a character array
rather than a string or cell array of strings.
By default, the Octave:erase:chararray 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-renderIf the Octave:glyph-render warning is enabled, Octave will
print a warning if the glyph for a character couldn’t be rendered with
the current font.
By 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:infinite-loopIf the Octave:infinite-loop warning is enabled, a warning is
printed when an infinite loop is detected such as for i = 1:Inf or
while (1).
By default, the Octave:infinite-loop warning is enabled.
Octave:language-extensionPrint warnings when using features that are unique to the Octave
language and that may still be missing in MATLAB.
By default, the Octave:language-extension warning is disabled.
The --traditional or --braindead startup options for
Octave may also be of use, see Command Line Options.
Octave:legacy-functionIf the Octave:legacy-function warning is enabled, a
warning is issued when Octave encounters a function that MATLAB has
suggested should be avoided. The function may become obsolete at some
point in the future and removed, in which case the warning will change to
Octave:deprecated-function, and the function will continue to exist
for two further versions of Octave before being removed.
By default, the Octave:legacy-function warning is enabled.
Octave:logical-conversionIf the Octave:logical-conversion warning is enabled, a warning is
printed if an implicit conversion of an array from numerical to boolean
occurs and any of the elements in the array are not equal to zero or one.
By default, the Octave:logical-conversion warning is enabled.
Octave:lu:sparse_inputIf the Octave:lu:sparse_input warning is enabled, Octave
will warn when the lu function is called with a sparse input and less than
four output arguments. In this case, sparsity-preserving column
permutations are not performed and the result may be inaccurate.
By default, the Octave:lu:sparse_input warning is enabled.
Octave:missing-glyphIf the Octave:glyph-render warning is enabled, Octave will
print a warning if the current font doesn’t provide a glyph for a
used character.
By 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:nearly-singular-matrixOctave:singular-matrixThese warnings are emitted if a (nearly) singular matrix is inverted.
By default, the Octave:nearly-singular-matrix and
Octave:singular-matrix warnings are enabled.
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:noninteger-range-as-indexIf the Octave:noninteger-range-as-index warning is enabled, a warning
is printed if an array is indexed with a range that contains non-integer
values. For example,
a = [1 2 3 4 5]; b = 2.2:4.2 ⇒ 1.2 2.2 3.2 a(b) ⇒ 2 3 4
elicits a warning if the Octave:noninteger-range-as-index warning is
enabled.
By default, the Octave:noninteger-range-as-index warning is enabled.
Octave:num-to-strIf the Octave:num-to-str warning is enabled, a warning is
printed for implicit conversions of numbers to their UTF-8 encoded 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 they do short
circuit when used in a condition.
By default, the Octave:possible-matlab-short-circuit-operator warning
is enabled.
Octave:recursive-path-searchIf the Octave:recursive-path-search warning is enabled, Octave
will issue a warning if addpath is used with double trailing
slashes.
By 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: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-functionIf the Octave:shadowed-function warning is enabled, Octave will
warn if a path is added to the search path that contains functions
that shadow core functions.
By 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:sqrtm:SingularMatrixIf the Octave:sqrtm:SingularMatrix warning is enabled, a warning is
printed if the matrix square root function sqrtm is called with an
input matrix that is singular.
By 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 UTF-8 encoded byte
sequences. 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:LaTeX:internal-errorIf the Octave:LaTeX:internal-error warning is enabled, a warning is
printed whenever the LaTeX renderer for text in plots encounters an issue.
By default, the Octave:LaTeX:internal-error warning is enabled.
Octave:unimplemented-matlab-functionalityIf the Octave:unimplemented-matlab-functionality warning is enabled,
a warning is printed when a MATLAB code construct is used which the
Octave interpreter parses as valid, but for which Octave does not yet
implement the functionality.
By default, the Octave:unimplemented-matlab-functionality 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]