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| <h3 class="section">8.4 Information About a Frame</h3> |
| |
| <p>There are several other commands to print information about the selected |
| stack frame. |
| |
| <dl> |
| <dt><code>frame</code><dt><code>f</code><dd>When used without any argument, this command does not change which |
| frame is selected, but prints a brief description of the currently |
| selected stack frame. It can be abbreviated <code>f</code>. With an |
| argument, this command is used to select a stack frame. |
| See <a href="Selection.html#Selection">Selecting a Frame</a>. |
| |
| <p><a name="index-info-frame-541"></a><a name="index-info-f-_0040r_007b_0028_0040code_007binfo-frame_007d_0029_007d-542"></a><br><dt><code>info frame</code><dt><code>info f</code><dd>This command prints a verbose description of the selected stack frame, |
| including: |
| |
| <ul> |
| <li>the address of the frame |
| <li>the address of the next frame down (called by this frame) |
| <li>the address of the next frame up (caller of this frame) |
| <li>the language in which the source code corresponding to this frame is written |
| <li>the address of the frame's arguments |
| <li>the address of the frame's local variables |
| <li>the program counter saved in it (the address of execution in the caller frame) |
| <li>which registers were saved in the frame |
| </ul> |
| |
| <p class="noindent">The verbose description is useful when |
| something has gone wrong that has made the stack format fail to fit |
| the usual conventions. |
| |
| <br><dt><code>info frame </code><span class="roman">[</span> <var>frame-selection-spec</var> <span class="roman">]</span><dt><code>info f </code><span class="roman">[</span> <var>frame-selection-spec</var> <span class="roman">]</span><dd>Print a verbose description of the frame selected by |
| <var>frame-selection-spec</var>. The <var>frame-selection-spec</var> is the |
| same as for the <samp><span class="command">frame</span></samp> command (see <a href="Selection.html#Selection">Selecting a Frame</a>). The selected frame remains unchanged by this command. |
| |
| <p><a name="index-info-args-543"></a><br><dt><code>info args [-q]</code><dd>Print the arguments of the selected frame, each on a separate line. |
| |
| <p>The optional flag ‘<samp><span class="samp">-q</span></samp>’, which stands for ‘<samp><span class="samp">quiet</span></samp>’, disables |
| printing header information and messages explaining why no argument |
| have been printed. |
| |
| <br><dt><code>info args [-q] [-t </code><var>type_regexp</var><code>] [</code><var>regexp</var><code>]</code><dd>Like <kbd>info args</kbd>, but only print the arguments selected |
| with the provided regexp(s). |
| |
| <p>If <var>regexp</var> is provided, print only the arguments whose names |
| match the regular expression <var>regexp</var>. |
| |
| <p>If <var>type_regexp</var> is provided, print only the arguments whose |
| types, as printed by the <code>whatis</code> command, match |
| the regular expression <var>type_regexp</var>. |
| If <var>type_regexp</var> contains space(s), it should be enclosed in |
| quote characters. If needed, use backslash to escape the meaning |
| of special characters or quotes. |
| |
| <p>If both <var>regexp</var> and <var>type_regexp</var> are provided, an argument |
| is printed only if its name matches <var>regexp</var> and its type matches |
| <var>type_regexp</var>. |
| |
| <br><dt><code>info locals [-q]</code><dd><a name="index-info-locals-544"></a>Print the local variables of the selected frame, each on a separate |
| line. These are all variables (declared either static or automatic) |
| accessible at the point of execution of the selected frame. |
| |
| <p>The optional flag ‘<samp><span class="samp">-q</span></samp>’, which stands for ‘<samp><span class="samp">quiet</span></samp>’, disables |
| printing header information and messages explaining why no local variables |
| have been printed. |
| |
| <br><dt><code>info locals [-q] [-t </code><var>type_regexp</var><code>] [</code><var>regexp</var><code>]</code><dd>Like <kbd>info locals</kbd>, but only print the local variables selected |
| with the provided regexp(s). |
| |
| <p>If <var>regexp</var> is provided, print only the local variables whose names |
| match the regular expression <var>regexp</var>. |
| |
| <p>If <var>type_regexp</var> is provided, print only the local variables whose |
| types, as printed by the <code>whatis</code> command, match |
| the regular expression <var>type_regexp</var>. |
| If <var>type_regexp</var> contains space(s), it should be enclosed in |
| quote characters. If needed, use backslash to escape the meaning |
| of special characters or quotes. |
| |
| <p>If both <var>regexp</var> and <var>type_regexp</var> are provided, a local variable |
| is printed only if its name matches <var>regexp</var> and its type matches |
| <var>type_regexp</var>. |
| |
| <p>The command <kbd>info locals -q -t </kbd><var>type_regexp</var> can usefully be |
| combined with the commands <kbd>frame apply</kbd> and <kbd>thread apply</kbd>. |
| For example, your program might use Resource Acquisition Is |
| Initialization types (RAII) such as <code>lock_something_t</code>: each |
| local variable of type <code>lock_something_t</code> automatically places a |
| lock that is destroyed when the variable goes out of scope. You can |
| then list all acquired locks in your program by doing |
| <pre class="smallexample"> thread apply all -s frame apply all -s info locals -q -t lock_something_t |
| </pre> |
| <p class="noindent">or the equivalent shorter form |
| <pre class="smallexample"> tfaas i lo -q -t lock_something_t |
| </pre> |
| </dl> |
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