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| <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> |
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