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 <a name="Convenience-Funs"></a>
 <div class="header">
 <p>
 Next: <a href="Registers.html#Registers" accesskey="n" rel="next">Registers</a>, Previous: <a href="Convenience-Vars.html#Convenience-Vars" accesskey="p" rel="prev">Convenience Vars</a>, Up: <a href="Data.html#Data" accesskey="u" rel="up">Data</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
 </div>
 <hr>
 <a name="Convenience-Functions"></a>
 <h3 class="section">10.12 Convenience Functions</h3>

 <a name="index-convenience-functions"></a>
 <p><small>GDB</small> also supplies some <em>convenience functions</em>.  These
 have a syntax similar to convenience variables.  A convenience
 function can be used in an expression just like an ordinary function;
 however, a convenience function is implemented internally to
 <small>GDB</small>.
 </p>
 <p>These functions do not require <small>GDB</small> to be configured with
 <code>Python</code> support, which means that they are always available.
 </p>
 <dl compact="compact">
 <dt><code>$_isvoid (<var>expr</var>)</code></dt>
 <dd><a name="index-_0024_005fisvoid_002c-convenience-function"></a>
 <p>Return one if the expression <var>expr</var> is <code>void</code>.  Otherwise it
 returns zero.
 </p>
 <p>A <code>void</code> expression is an expression where the type of the result
 is <code>void</code>.  For example, you can examine a convenience variable
 (see <a href="Convenience-Vars.html#Convenience-Vars">Convenience Variables</a>) to check whether
 it is <code>void</code>:
 </p>
 <div class="smallexample">
 <pre class="smallexample">(gdb) print $_exitcode
 $1 = void
 (gdb) print $_isvoid ($_exitcode)
 $2 = 1
 (gdb) run
 Starting program: ./a.out
 [Inferior 1 (process 29572) exited normally]
 (gdb) print $_exitcode
 $3 = 0
 (gdb) print $_isvoid ($_exitcode)
 $4 = 0
 </pre></div>

 <p>In the example above, we used <code>$_isvoid</code> to check whether
 <code>$_exitcode</code> is <code>void</code> before and after the execution of the
 program being debugged.  Before the execution there is no exit code to
 be examined, therefore <code>$_exitcode</code> is <code>void</code>.  After the
 execution the program being debugged returned zero, therefore
 <code>$_exitcode</code> is zero, which means that it is not <code>void</code>
 anymore.
 </p>
 <p>The <code>void</code> expression can also be a call of a function from the
 program being debugged.  For example, given the following function:
 </p>
 <div class="smallexample">
 <pre class="smallexample">void
 foo (void)
 {
 }
 </pre></div>

 <p>The result of calling it inside <small>GDB</small> is <code>void</code>:
 </p>
 <div class="smallexample">
 <pre class="smallexample">(gdb) print foo ()
 $1 = void
 (gdb) print $_isvoid (foo ())
 $2 = 1
 (gdb) set $v = foo ()
 (gdb) print $v
 $3 = void
 (gdb) print $_isvoid ($v)
 $4 = 1
 </pre></div>

 </dd>
 </dl>

 <p>These functions require <small>GDB</small> to be configured with
 <code>Python</code> support.
 </p>
 <dl compact="compact">
 <dt><code>$_memeq(<var>buf1</var>, <var>buf2</var>, <var>length</var>)</code></dt>
 <dd><a name="index-_0024_005fmemeq_002c-convenience-function"></a>
 <p>Returns one if the <var>length</var> bytes at the addresses given by
 <var>buf1</var> and <var>buf2</var> are equal.
 Otherwise it returns zero.
 </p>
 </dd>
 <dt><code>$_regex(<var>str</var>, <var>regex</var>)</code></dt>
 <dd><a name="index-_0024_005fregex_002c-convenience-function"></a>
 <p>Returns one if the string <var>str</var> matches the regular expression
 <var>regex</var>.  Otherwise it returns zero.
 The syntax of the regular expression is that specified by <code>Python</code>&rsquo;s
 regular expression support.
 </p>
 </dd>
 <dt><code>$_streq(<var>str1</var>, <var>str2</var>)</code></dt>
 <dd><a name="index-_0024_005fstreq_002c-convenience-function"></a>
 <p>Returns one if the strings <var>str1</var> and <var>str2</var> are equal.
 Otherwise it returns zero.
 </p>
 </dd>
 <dt><code>$_strlen(<var>str</var>)</code></dt>
 <dd><a name="index-_0024_005fstrlen_002c-convenience-function"></a>
 <p>Returns the length of string <var>str</var>.
 </p>
 </dd>
 <dt><code>$_caller_is(<var>name</var><span class="roman">[</span>, <var>number_of_frames</var><span class="roman">]</span>)</code></dt>
 <dd><a name="index-_0024_005fcaller_005fis_002c-convenience-function"></a>
 <p>Returns one if the calling function&rsquo;s name is equal to <var>name</var>.
 Otherwise it returns zero.
 </p>
 <p>If the optional argument <var>number_of_frames</var> is provided,
 it is the number of frames up in the stack to look.
 The default is 1.
 </p>
 <p>Example:
 </p>
 <div class="smallexample">
 <pre class="smallexample">(gdb) backtrace
 #0  bottom_func ()
     at testsuite/gdb.python/py-caller-is.c:21
 #1  0x00000000004005a0 in middle_func ()
     at testsuite/gdb.python/py-caller-is.c:27
 #2  0x00000000004005ab in top_func ()
     at testsuite/gdb.python/py-caller-is.c:33
 #3  0x00000000004005b6 in main ()
     at testsuite/gdb.python/py-caller-is.c:39
 (gdb) print $_caller_is (&quot;middle_func&quot;)
 $1 = 1
 (gdb) print $_caller_is (&quot;top_func&quot;, 2)
 $1 = 1
 </pre></div>

 </dd>
 <dt><code>$_caller_matches(<var>regexp</var><span class="roman">[</span>, <var>number_of_frames</var><span class="roman">]</span>)</code></dt>
 <dd><a name="index-_0024_005fcaller_005fmatches_002c-convenience-function"></a>
 <p>Returns one if the calling function&rsquo;s name matches the regular expression
 <var>regexp</var>.  Otherwise it returns zero.
 </p>
 <p>If the optional argument <var>number_of_frames</var> is provided,
 it is the number of frames up in the stack to look.
 The default is 1.
 </p>
 </dd>
 <dt><code>$_any_caller_is(<var>name</var><span class="roman">[</span>, <var>number_of_frames</var><span class="roman">]</span>)</code></dt>
 <dd><a name="index-_0024_005fany_005fcaller_005fis_002c-convenience-function"></a>
 <p>Returns one if any calling function&rsquo;s name is equal to <var>name</var>.
 Otherwise it returns zero.
 </p>
 <p>If the optional argument <var>number_of_frames</var> is provided,
 it is the number of frames up in the stack to look.
 The default is 1.
 </p>
 <p>This function differs from <code>$_caller_is</code> in that this function
 checks all stack frames from the immediate caller to the frame specified
 by <var>number_of_frames</var>, whereas <code>$_caller_is</code> only checks the
 frame specified by <var>number_of_frames</var>.
 </p>
 </dd>
 <dt><code>$_any_caller_matches(<var>regexp</var><span class="roman">[</span>, <var>number_of_frames</var><span class="roman">]</span>)</code></dt>
 <dd><a name="index-_0024_005fany_005fcaller_005fmatches_002c-convenience-function"></a>
 <p>Returns one if any calling function&rsquo;s name matches the regular expression
 <var>regexp</var>.  Otherwise it returns zero.
 </p>
 <p>If the optional argument <var>number_of_frames</var> is provided,
 it is the number of frames up in the stack to look.
 The default is 1.
 </p>
 <p>This function differs from <code>$_caller_matches</code> in that this function
 checks all stack frames from the immediate caller to the frame specified
 by <var>number_of_frames</var>, whereas <code>$_caller_matches</code> only checks the
 frame specified by <var>number_of_frames</var>.
 </p>
 </dd>
 </dl>

 <p><small>GDB</small> provides the ability to list and get help on
 convenience functions.
 </p>
 <dl compact="compact">
 <dt><code>help function</code></dt>
 <dd><a name="index-help-function"></a>
 <a name="index-show-all-convenience-functions"></a>
 <p>Print a list of all convenience functions.
 </p></dd>
 </dl>

 <hr>
 <div class="header">
 <p>
 Next: <a href="Registers.html#Registers" accesskey="n" rel="next">Registers</a>, Previous: <a href="Convenience-Vars.html#Convenience-Vars" accesskey="p" rel="prev">Convenience Vars</a>, Up: <a href="Data.html#Data" accesskey="u" rel="up">Data</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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	<a name="Convenience-Funs"></a>
	<div class="header">
	<p>
	Next: <a href="Registers.html#Registers" accesskey="n" rel="next">Registers</a>, Previous: <a href="Convenience-Vars.html#Convenience-Vars" accesskey="p" rel="prev">Convenience Vars</a>, Up: <a href="Data.html#Data" accesskey="u" rel="up">Data</a>   [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
	</div>
	<hr>
	<a name="Convenience-Functions"></a>
	<h3 class="section">10.12 Convenience Functions</h3>

	<a name="index-convenience-functions"></a>
	<p><small>GDB</small> also supplies some <em>convenience functions</em>. These
	have a syntax similar to convenience variables. A convenience
	function can be used in an expression just like an ordinary function;
	however, a convenience function is implemented internally to
	<small>GDB</small>.
	</p>
	<p>These functions do not require <small>GDB</small> to be configured with
	<code>Python</code> support, which means that they are always available.
	</p>
	<dl compact="compact">
	<dt><code>$_isvoid (<var>expr</var>)</code></dt>
	<dd><a name="index-_0024_005fisvoid_002c-convenience-function"></a>
	<p>Return one if the expression <var>expr</var> is <code>void</code>. Otherwise it
	returns zero.
	</p>
	<p>A <code>void</code> expression is an expression where the type of the result
	is <code>void</code>. For example, you can examine a convenience variable
	(see <a href="Convenience-Vars.html#Convenience-Vars">Convenience Variables</a>) to check whether
	it is <code>void</code>:
	</p>
	<div class="smallexample">
	<pre class="smallexample">(gdb) print $_exitcode
	$1 = void
	(gdb) print $_isvoid ($_exitcode)
	$2 = 1
	(gdb) run
	Starting program: ./a.out
	[Inferior 1 (process 29572) exited normally]
	(gdb) print $_exitcode
	$3 = 0
	(gdb) print $_isvoid ($_exitcode)
	$4 = 0
	</pre></div>

	<p>In the example above, we used <code>$_isvoid</code> to check whether
	<code>$_exitcode</code> is <code>void</code> before and after the execution of the
	program being debugged. Before the execution there is no exit code to
	be examined, therefore <code>$_exitcode</code> is <code>void</code>. After the
	execution the program being debugged returned zero, therefore
	<code>$_exitcode</code> is zero, which means that it is not <code>void</code>
	anymore.
	</p>
	<p>The <code>void</code> expression can also be a call of a function from the
	program being debugged. For example, given the following function:
	</p>
	<div class="smallexample">
	<pre class="smallexample">void
	foo (void)
	{
	}
	</pre></div>

	<p>The result of calling it inside <small>GDB</small> is <code>void</code>:
	</p>
	<div class="smallexample">
	<pre class="smallexample">(gdb) print foo ()
	$1 = void
	(gdb) print $_isvoid (foo ())
	$2 = 1
	(gdb) set $v = foo ()
	(gdb) print $v
	$3 = void
	(gdb) print $_isvoid ($v)
	$4 = 1
	</pre></div>

	</dd>
	</dl>

	<p>These functions require <small>GDB</small> to be configured with
	<code>Python</code> support.
	</p>
	<dl compact="compact">
	<dt><code>$_memeq(<var>buf1</var>, <var>buf2</var>, <var>length</var>)</code></dt>
	<dd><a name="index-_0024_005fmemeq_002c-convenience-function"></a>
	<p>Returns one if the <var>length</var> bytes at the addresses given by
	<var>buf1</var> and <var>buf2</var> are equal.
	Otherwise it returns zero.
	</p>
	</dd>
	<dt><code>$_regex(<var>str</var>, <var>regex</var>)</code></dt>
	<dd><a name="index-_0024_005fregex_002c-convenience-function"></a>
	<p>Returns one if the string <var>str</var> matches the regular expression
	<var>regex</var>. Otherwise it returns zero.
	The syntax of the regular expression is that specified by <code>Python</code>’s
	regular expression support.
	</p>
	</dd>
	<dt><code>$_streq(<var>str1</var>, <var>str2</var>)</code></dt>
	<dd><a name="index-_0024_005fstreq_002c-convenience-function"></a>
	<p>Returns one if the strings <var>str1</var> and <var>str2</var> are equal.
	Otherwise it returns zero.
	</p>
	</dd>
	<dt><code>$_strlen(<var>str</var>)</code></dt>
	<dd><a name="index-_0024_005fstrlen_002c-convenience-function"></a>
	<p>Returns the length of string <var>str</var>.
	</p>
	</dd>
	<dt><code>$_caller_is(<var>name</var><span class="roman">[</span>, <var>number_of_frames</var><span class="roman">]</span>)</code></dt>
	<dd><a name="index-_0024_005fcaller_005fis_002c-convenience-function"></a>
	<p>Returns one if the calling function’s name is equal to <var>name</var>.
	Otherwise it returns zero.
	</p>
	<p>If the optional argument <var>number_of_frames</var> is provided,
	it is the number of frames up in the stack to look.
	The default is 1.
	</p>
	<p>Example:
	</p>
	<div class="smallexample">
	<pre class="smallexample">(gdb) backtrace
	#0 bottom_func ()
	at testsuite/gdb.python/py-caller-is.c:21
	#1 0x00000000004005a0 in middle_func ()
	at testsuite/gdb.python/py-caller-is.c:27
	#2 0x00000000004005ab in top_func ()
	at testsuite/gdb.python/py-caller-is.c:33
	#3 0x00000000004005b6 in main ()
	at testsuite/gdb.python/py-caller-is.c:39
	(gdb) print $_caller_is ("middle_func")
	$1 = 1
	(gdb) print $_caller_is ("top_func", 2)
	$1 = 1
	</pre></div>

	</dd>
	<dt><code>$_caller_matches(<var>regexp</var><span class="roman">[</span>, <var>number_of_frames</var><span class="roman">]</span>)</code></dt>
	<dd><a name="index-_0024_005fcaller_005fmatches_002c-convenience-function"></a>
	<p>Returns one if the calling function’s name matches the regular expression
	<var>regexp</var>. Otherwise it returns zero.
	</p>
	<p>If the optional argument <var>number_of_frames</var> is provided,
	it is the number of frames up in the stack to look.
	The default is 1.
	</p>
	</dd>
	<dt><code>$_any_caller_is(<var>name</var><span class="roman">[</span>, <var>number_of_frames</var><span class="roman">]</span>)</code></dt>
	<dd><a name="index-_0024_005fany_005fcaller_005fis_002c-convenience-function"></a>
	<p>Returns one if any calling function’s name is equal to <var>name</var>.
	Otherwise it returns zero.
	</p>
	<p>If the optional argument <var>number_of_frames</var> is provided,
	it is the number of frames up in the stack to look.
	The default is 1.
	</p>
	<p>This function differs from <code>$_caller_is</code> in that this function
	checks all stack frames from the immediate caller to the frame specified
	by <var>number_of_frames</var>, whereas <code>$_caller_is</code> only checks the
	frame specified by <var>number_of_frames</var>.
	</p>
	</dd>
	<dt><code>$_any_caller_matches(<var>regexp</var><span class="roman">[</span>, <var>number_of_frames</var><span class="roman">]</span>)</code></dt>
	<dd><a name="index-_0024_005fany_005fcaller_005fmatches_002c-convenience-function"></a>
	<p>Returns one if any calling function’s name matches the regular expression
	<var>regexp</var>. Otherwise it returns zero.
	</p>
	<p>If the optional argument <var>number_of_frames</var> is provided,
	it is the number of frames up in the stack to look.
	The default is 1.
	</p>
	<p>This function differs from <code>$_caller_matches</code> in that this function
	checks all stack frames from the immediate caller to the frame specified
	by <var>number_of_frames</var>, whereas <code>$_caller_matches</code> only checks the
	frame specified by <var>number_of_frames</var>.
	</p>
	</dd>
	</dl>

	<p><small>GDB</small> provides the ability to list and get help on
	convenience functions.
	</p>
	<dl compact="compact">
	<dt><code>help function</code></dt>
	<dd><a name="index-help-function"></a>
	<a name="index-show-all-convenience-functions"></a>
	<p>Print a list of all convenience functions.
	</p></dd>
	</dl>

	<hr>
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