98 lines
5.1 KiB
HTML
98 lines
5.1 KiB
HTML
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<html lang="en">
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<head>
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<title>Thread-Specific Breakpoints - Debugging with GDB</title>
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<link rel="up" href="Thread-Stops.html#Thread-Stops" title="Thread Stops">
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<link rel="prev" href="Background-Execution.html#Background-Execution" title="Background Execution">
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<body>
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<div class="node">
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<a name="Thread-Specific-Breakpoints"></a>
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<a name="Thread_002dSpecific-Breakpoints"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Interrupted-System-Calls.html#Interrupted-System-Calls">Interrupted System Calls</a>,
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Previous: <a rel="previous" accesskey="p" href="Background-Execution.html#Background-Execution">Background Execution</a>,
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Up: <a rel="up" accesskey="u" href="Thread-Stops.html#Thread-Stops">Thread Stops</a>
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<hr>
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</div>
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<h4 class="subsection">5.5.4 Thread-Specific Breakpoints</h4>
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<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
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breakpoints on all threads, or on a particular thread.
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<a name="index-breakpoints-and-threads-428"></a>
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<a name="index-thread-breakpoints-429"></a>
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<a name="index-break-_0040dots_007b_007d-thread-_0040var_007bthread_002did_007d-430"></a>
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<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
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writing them (see <a href="Specify-Location.html#Specify-Location">Specify Location</a>), but the effect is always to
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specify some source line.
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<p>Use the qualifier ‘<samp><span class="samp">thread </span><var>thread-id</var></samp>’ with a breakpoint command
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to specify that you only want <span class="sc">gdb</span> to stop the program when a
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particular thread reaches this breakpoint. The <var>thread-id</var> specifier
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is one of the thread identifiers assigned by <span class="sc">gdb</span>, shown
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in the first column of the ‘<samp><span class="samp">info threads</span></samp>’ display.
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<p>If you do not specify ‘<samp><span class="samp">thread </span><var>thread-id</var></samp>’ when you set a
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breakpoint, the breakpoint applies to <em>all</em> threads of your
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program.
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<p>You can use the <code>thread</code> qualifier on conditional breakpoints as
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well; in this case, place ‘<samp><span class="samp">thread </span><var>thread-id</var></samp>’ before or
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after the breakpoint condition, like this:
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<pre class="smallexample"> (gdb) break frik.c:13 thread 28 if bartab > lim
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</pre>
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</dl>
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<p>Thread-specific breakpoints are automatically deleted when
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<span class="sc">gdb</span> detects the corresponding thread is no longer in the
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thread list. For example:
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<pre class="smallexample"> (gdb) c
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Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
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</pre>
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<p>There are several ways for a thread to disappear, such as a regular
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thread exit, but also when you detach from the process with the
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<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
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(see <a href="Remote-Debugging.html#Remote-Debugging">Remote Debugging</a>), etc. Note that with some targets,
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<span class="sc">gdb</span> is only able to detect a thread has exited when the user
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explictly asks for the thread list with the <code>info threads</code>
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command.
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</body></html>
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