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| <h3 class="section">10.12 Convenience Functions</h3> |
| |
| <p><a name="index-convenience-functions-736"></a><span class="sc">gdb</span> also supplies some <dfn>convenience functions</dfn>. 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 |
| <span class="sc">gdb</span>. |
| |
| <p>These functions do not require <span class="sc">gdb</span> to be configured with |
| <code>Python</code> support, which means that they are always available. |
| |
| <dl> |
| <dt><code>$_isvoid (</code><var>expr</var><code>)</code><dd><a name="index-g_t_0024_005fisvoid_0040r_007b_002c-convenience-function_007d-737"></a>Return one if the expression <var>expr</var> is <code>void</code>. Otherwise it |
| returns zero. |
| |
| <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>: |
| |
| <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) |
| $4 = 0 |
| </pre> |
| <p>In the example above, we used <code>$_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>The <code>void</code> expression can also be a call of a function from the |
| program being debugged. For example, given the following function: |
| |
| <pre class="smallexample"> void |
| foo (void) |
| { |
| } |
| </pre> |
| <p>The result of calling it inside <span class="sc">gdb</span> is <code>void</code>: |
| |
| <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) |
| $4 = 1 |
| </pre> |
| </dl> |
| |
| <p>These functions require <span class="sc">gdb</span> to be configured with |
| <code>Python</code> support. |
| |
| <dl> |
| <dt><code>$_memeq(</code><var>buf1</var><code>, </code><var>buf2</var><code>, </code><var>length</var><code>)</code><dd><a name="index-g_t_0024_005fmemeq_0040r_007b_002c-convenience-function_007d-738"></a>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. |
| |
| <br><dt><code>$_regex(</code><var>str</var><code>, </code><var>regex</var><code>)</code><dd><a name="index-g_t_0024_005fregex_0040r_007b_002c-convenience-function_007d-739"></a>Returns one if the string <var>str</var> matches the regular expression |
| <var>regex</var>. Otherwise it returns zero. |
| The syntax of the regular expression is that specified by <code>Python</code>'s |
| regular expression support. |
| |
| <br><dt><code>$_streq(</code><var>str1</var><code>, </code><var>str2</var><code>)</code><dd><a name="index-g_t_0024_005fstreq_0040r_007b_002c-convenience-function_007d-740"></a>Returns one if the strings <var>str1</var> and <var>str2</var> are equal. |
| Otherwise it returns zero. |
| |
| <br><dt><code>$_strlen(</code><var>str</var><code>)</code><dd><a name="index-g_t_0024_005fstrlen_0040r_007b_002c-convenience-function_007d-741"></a>Returns the length of string <var>str</var>. |
| |
| <br><dt><code>$_caller_is(</code><var>name</var><span class="roman">[</span><code>, </code><var>number_of_frames</var><span class="roman">]</span><code>)</code><dd><a name="index-g_t_0024_005fcaller_005fis_0040r_007b_002c-convenience-function_007d-742"></a>Returns one if the calling function's name is equal to <var>name</var>. |
| Otherwise it returns zero. |
| |
| <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>Example: |
| |
| <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) |
| $1 = 1 |
| </pre> |
| <br><dt><code>$_caller_matches(</code><var>regexp</var><span class="roman">[</span><code>, </code><var>number_of_frames</var><span class="roman">]</span><code>)</code><dd><a name="index-g_t_0024_005fcaller_005fmatches_0040r_007b_002c-convenience-function_007d-743"></a>Returns one if the calling function's name matches the regular expression |
| <var>regexp</var>. Otherwise it returns zero. |
| |
| <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. |
| |
| <br><dt><code>$_any_caller_is(</code><var>name</var><span class="roman">[</span><code>, </code><var>number_of_frames</var><span class="roman">]</span><code>)</code><dd><a name="index-g_t_0024_005fany_005fcaller_005fis_0040r_007b_002c-convenience-function_007d-744"></a>Returns one if any calling function's name is equal to <var>name</var>. |
| Otherwise it returns zero. |
| |
| <p>If the optional argument <var>number_of_frames</var> is provided, |
| it is the number of frames up in the stack to look. |
| The default is 1. |
| |
| <p>This function differs from <code>$_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>$_caller_is</code> only checks the |
| frame specified by <var>number_of_frames</var>. |
| |
| <br><dt><code>$_any_caller_matches(</code><var>regexp</var><span class="roman">[</span><code>, </code><var>number_of_frames</var><span class="roman">]</span><code>)</code><dd><a name="index-g_t_0024_005fany_005fcaller_005fmatches_0040r_007b_002c-convenience-function_007d-745"></a>Returns one if any calling function's name matches the regular expression |
| <var>regexp</var>. Otherwise it returns zero. |
| |
| <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>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>. |
| |
| <br><dt><code>$_as_string(</code><var>value</var><code>)</code><dd><a name="index-g_t_0024_005fas_005fstring_0040r_007b_002c-convenience-function_007d-746"></a>Return the string representation of <var>value</var>. |
| |
| <p>This function is useful to obtain the textual label (enumerator) of an |
| enumeration value. For example, assuming the variable <var>node</var> is of |
| an enumerated type: |
| |
| <pre class="smallexample"> (gdb) printf "Visiting node of type %s\n", $_as_string(node) |
| Visiting node of type NODE_INTEGER |
| </pre> |
| </dl> |
| |
| <p><span class="sc">gdb</span> provides the ability to list and get help on |
| convenience functions. |
| |
| <dl> |
| <dt><code>help function</code><dd><a name="index-help-function-747"></a><a name="index-show-all-convenience-functions-748"></a>Print a list of all convenience functions. |
| </dl> |
| |
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| |
