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| <h3 class="section">8.3 Selecting a Frame</h3> |
| |
| <p>Most commands for examining the stack and other data in your program work on |
| whichever stack frame is selected at the moment. Here are the commands for |
| selecting a stack frame; all of them finish by printing a brief description |
| of the stack frame just selected. |
| |
| |
| <a name="index-frame_0040r_007b_002c-selecting_007d-425"></a> |
| <a name="index-f-_0040r_007b_0028_0040code_007bframe_007d_0029_007d-426"></a> |
| <dl><dt><code>frame </code><var>n</var><dt><code>f </code><var>n</var><dd>Select frame number <var>n</var>. Recall that frame zero is the innermost |
| (currently executing) frame, frame one is the frame that called the |
| innermost one, and so on. The highest-numbered frame is the one for |
| <code>main</code>. |
| |
| <br><dt><code>frame </code><var>addr</var><dt><code>f </code><var>addr</var><dd>Select the frame at address <var>addr</var>. This is useful mainly if the |
| chaining of stack frames has been damaged by a bug, making it |
| impossible for <span class="sc">gdb</span> to assign numbers properly to all frames. In |
| addition, this can be useful when your program has multiple stacks and |
| switches between them. |
| |
| <p>On the MIPS and Alpha architectures, <code>frame</code> needs two addresses to |
| select an arbitrary frame: a stack pointer and a program counter. |
| |
| <p><a name="index-up-427"></a><br><dt><code>up </code><var>n</var><dd>Move <var>n</var> frames up the stack. For positive numbers <var>n</var>, this |
| advances toward the outermost frame, to higher frame numbers, to frames |
| that have existed longer. <var>n</var> defaults to one. |
| |
| <p><a name="index-down-428"></a><a name="index-do-_0040r_007b_0028_0040code_007bdown_007d_0029_007d-429"></a><br><dt><code>down </code><var>n</var><dd>Move <var>n</var> frames down the stack. For positive numbers <var>n</var>, this |
| advances toward the innermost frame, to lower frame numbers, to frames |
| that were created more recently. <var>n</var> defaults to one. You may |
| abbreviate <code>down</code> as <code>do</code>. |
| </dl> |
| |
| <p>All of these commands end by printing two lines of output describing the |
| frame. The first line shows the frame number, the function name, the |
| arguments, and the source file and line number of execution in that |
| frame. The second line shows the text of that source line. |
| |
| <p>For example: |
| |
| <pre class="smallexample"> (gdb) up |
| #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc) |
| at env.c:10 |
| 10 read_input_file (argv[i]); |
| </pre> |
| <p>After such a printout, the <code>list</code> command with no arguments |
| prints ten lines centered on the point of execution in the frame. |
| You can also edit the program at the point of execution with your favorite |
| editing program by typing <code>edit</code>. |
| See <a href="List.html#List">Printing Source Lines</a>, |
| for details. |
| |
| |
| <a name="index-down_002dsilently-430"></a> |
| <a name="index-up_002dsilently-431"></a> |
| <dl><dt><code>up-silently </code><var>n</var><dt><code>down-silently </code><var>n</var><dd>These two commands are variants of <code>up</code> and <code>down</code>, |
| respectively; they differ in that they do their work silently, without |
| causing display of the new frame. They are intended primarily for use |
| in <span class="sc">gdb</span> command scripts, where the output might be unnecessary and |
| distracting. |
| </dl> |
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