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<a name="Thread_002dSpecific-Breakpoints"></a>
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<a name="Thread_002dSpecific-Breakpoints-1"></a>
<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.
</p>
<dl compact="compact">
<dd><a name="index-breakpoints-and-threads"></a>
<a name="index-thread-breakpoints"></a>
<a name="index-break-_2026-thread-thread_002did"></a>
</dd>
<dt><code>break <var>location</var> thread <var>thread-id</var></code></dt>
<dt><code>break <var>location</var> thread <var>thread-id</var> if &hellip;</code></dt>
<dd><p><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>
<p>Use the qualifier &lsquo;<samp>thread <var>thread-id</var></samp>&rsquo; with a breakpoint command
to specify that you only want <small>GDB</small> 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 <small>GDB</small>, shown
in the first column of the &lsquo;<samp>info threads</samp>&rsquo; display.
</p>
<p>If you do not specify &lsquo;<samp>thread <var>thread-id</var></samp>&rsquo; when you set a
breakpoint, the breakpoint applies to <em>all</em> threads of your
program.
</p>
<p>You can use the <code>thread</code> qualifier on conditional breakpoints as
well; in this case, place &lsquo;<samp>thread <var>thread-id</var></samp>&rsquo; before or
after the breakpoint condition, like this:
</p>
<div class="smallexample">
<pre class="smallexample">(gdb) break frik.c:13 thread 28 if bartab &gt; lim
</pre></div>

</dd>
</dl>

<p>Thread-specific breakpoints are automatically deleted when
<small>GDB</small> detects the corresponding thread is no longer in the
thread list.  For example:
</p>
<div class="smallexample">
<pre class="smallexample">(gdb) c
Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
</pre></div>

<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 <small>GDB</small> loses the remote connection
(see <a href="Remote-Debugging.html#Remote-Debugging">Remote Debugging</a>), etc.  Note that with some targets,
<small>GDB</small> 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.
</p>
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