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| <h3 class="section">17.5 Calling Program Functions</h3> |
| |
| |
| <a name="index-calling-functions-933"></a> |
| <a name="index-inferior-functions_002c-calling-934"></a> |
| <dl><dt><code>print </code><var>expr</var><dd>Evaluate the expression <var>expr</var> and display the resulting value. |
| <var>expr</var> may include calls to functions in the program being |
| debugged. |
| |
| <p><a name="index-call-935"></a><br><dt><code>call </code><var>expr</var><dd>Evaluate the expression <var>expr</var> without displaying <code>void</code> |
| returned values. |
| |
| <p>You can use this variant of the <code>print</code> command if you want to |
| execute a function from your program that does not return anything |
| (a.k.a. <dfn>a void function</dfn>), but without cluttering the output |
| with <code>void</code> returned values that <span class="sc">gdb</span> will otherwise |
| print. If the result is not void, it is printed and saved in the |
| value history. |
| </dl> |
| |
| <p>It is possible for the function you call via the <code>print</code> or |
| <code>call</code> command to generate a signal (e.g., if there's a bug in |
| the function, or if you passed it incorrect arguments). What happens |
| in that case is controlled by the <code>set unwindonsignal</code> command. |
| |
| <p>Similarly, with a C<tt>++</tt> program it is possible for the function you |
| call via the <code>print</code> or <code>call</code> command to generate an |
| exception that is not handled due to the constraints of the dummy |
| frame. In this case, any exception that is raised in the frame, but has |
| an out-of-frame exception handler will not be found. GDB builds a |
| dummy-frame for the inferior function call, and the unwinder cannot |
| seek for exception handlers outside of this dummy-frame. What happens |
| in that case is controlled by the |
| <code>set unwind-on-terminating-exception</code> command. |
| |
| <dl> |
| <dt><code>set unwindonsignal</code><dd><a name="index-set-unwindonsignal-936"></a><a name="index-unwind-stack-in-called-functions-937"></a><a name="index-call-dummy-stack-unwinding-938"></a>Set unwinding of the stack if a signal is received while in a function |
| that <span class="sc">gdb</span> called in the program being debugged. If set to on, |
| <span class="sc">gdb</span> unwinds the stack it created for the call and restores |
| the context to what it was before the call. If set to off (the |
| default), <span class="sc">gdb</span> stops in the frame where the signal was |
| received. |
| |
| <br><dt><code>show unwindonsignal</code><dd><a name="index-show-unwindonsignal-939"></a>Show the current setting of stack unwinding in the functions called by |
| <span class="sc">gdb</span>. |
| |
| <br><dt><code>set unwind-on-terminating-exception</code><dd><a name="index-set-unwind_002don_002dterminating_002dexception-940"></a><a name="index-unwind-stack-in-called-functions-with-unhandled-exceptions-941"></a><a name="index-call-dummy-stack-unwinding-on-unhandled-exception_002e-942"></a>Set unwinding of the stack if a C<tt>++</tt> exception is raised, but left |
| unhandled while in a function that <span class="sc">gdb</span> called in the program being |
| debugged. If set to on (the default), <span class="sc">gdb</span> unwinds the stack |
| it created for the call and restores the context to what it was before |
| the call. If set to off, <span class="sc">gdb</span> the exception is delivered to |
| the default C<tt>++</tt> exception handler and the inferior terminated. |
| |
| <br><dt><code>show unwind-on-terminating-exception</code><dd><a name="index-show-unwind_002don_002dterminating_002dexception-943"></a>Show the current setting of stack unwinding in the functions called by |
| <span class="sc">gdb</span>. |
| |
| </dl> |
| |
| <p><a name="index-weak-alias-functions-944"></a>Sometimes, a function you wish to call is actually a <dfn>weak alias</dfn> |
| for another function. In such case, <span class="sc">gdb</span> might not pick up |
| the type information, including the types of the function arguments, |
| which causes <span class="sc">gdb</span> to call the inferior function incorrectly. |
| As a result, the called function will function erroneously and may |
| even crash. A solution to that is to use the name of the aliased |
| function instead. |
| |
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