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| <h4 class="subsection">5.5.4 Thread-Specific Breakpoints</h4> |
| |
| <p>When your program has multiple threads (see <a href="Threads.html#Threads">Debugging Programs with Multiple Threads</a>), you can choose whether to set |
| breakpoints on all threads, or on a particular thread. |
| |
| |
| <a name="index-breakpoints-and-threads-428"></a> |
| <a name="index-thread-breakpoints-429"></a> |
| <a name="index-break-_0040dots_007b_007d-thread-_0040var_007bthread_002did_007d-430"></a> |
| <dl><dt><code>break </code><var>location</var><code> thread </code><var>thread-id</var><dt><code>break </code><var>location</var><code> thread </code><var>thread-id</var><code> if ...</code><dd><var>location</var> specifies source lines; there are several ways of |
| writing them (see <a href="Specify-Location.html#Specify-Location">Specify Location</a>), but the effect is always to |
| specify some source line. |
| |
| <p>Use the qualifier ‘<samp><span class="samp">thread </span><var>thread-id</var></samp>’ with a breakpoint command |
| to specify that you only want <span class="sc">gdb</span> to stop the program when a |
| particular thread reaches this breakpoint. The <var>thread-id</var> specifier |
| is one of the thread identifiers assigned by <span class="sc">gdb</span>, shown |
| in the first column of the ‘<samp><span class="samp">info threads</span></samp>’ display. |
| |
| <p>If you do not specify ‘<samp><span class="samp">thread </span><var>thread-id</var></samp>’ when you set a |
| breakpoint, the breakpoint applies to <em>all</em> threads of your |
| program. |
| |
| <p>You can use the <code>thread</code> qualifier on conditional breakpoints as |
| well; in this case, place ‘<samp><span class="samp">thread </span><var>thread-id</var></samp>’ before or |
| after the breakpoint condition, like this: |
| |
| <pre class="smallexample"> (gdb) break frik.c:13 thread 28 if bartab > lim |
| </pre> |
| </dl> |
| |
| <p>Thread-specific breakpoints are automatically deleted when |
| <span class="sc">gdb</span> detects the corresponding thread is no longer in the |
| thread list. For example: |
| |
| <pre class="smallexample"> (gdb) c |
| Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list. |
| </pre> |
| <p>There are several ways for a thread to disappear, such as a regular |
| thread exit, but also when you detach from the process with the |
| <code>detach</code> command (see <a href="Attach.html#Attach">Debugging an Already-running Process</a>), or if <span class="sc">gdb</span> loses the remote connection |
| (see <a href="Remote-Debugging.html#Remote-Debugging">Remote Debugging</a>), etc. Note that with some targets, |
| <span class="sc">gdb</span> is only able to detect a thread has exited when the user |
| explictly asks for the thread list with the <code>info threads</code> |
| command. |
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