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136 lines
6.5 KiB
HTML
136 lines
6.5 KiB
HTML
4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- Copyright (C) 1988-2019 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with the
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Invariant Sections being "Free Software" and "Free Software Needs
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Free Documentation", with the Front-Cover Texts being "A GNU Manual,"
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and with the Back-Cover Texts as in (a) below.
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(a) The FSF's Back-Cover Text is: "You are free to copy and modify
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this GNU Manual. Buying copies from GNU Press supports the FSF in
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developing GNU and promoting software freedom." -->
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Thread-Specific Breakpoints (Debugging with GDB)</title>
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<meta name="description" content="Thread-Specific Breakpoints (Debugging with GDB)">
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<meta name="keywords" content="Thread-Specific Breakpoints (Debugging with GDB)">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Thread-Stops.html#Thread-Stops" rel="up" title="Thread Stops">
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<link href="Interrupted-System-Calls.html#Interrupted-System-Calls" rel="next" title="Interrupted System Calls">
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<link href="Background-Execution.html#Background-Execution" rel="prev" title="Background Execution">
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</style>
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</head>
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<body lang="en">
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<a name="Thread_002dSpecific-Breakpoints"></a>
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<div class="header">
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<p>
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Next: <a href="Interrupted-System-Calls.html#Interrupted-System-Calls" accesskey="n" rel="next">Interrupted System Calls</a>, Previous: <a href="Background-Execution.html#Background-Execution" accesskey="p" rel="prev">Background Execution</a>, Up: <a href="Thread-Stops.html#Thread-Stops" accesskey="u" rel="up">Thread Stops</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Thread_002dSpecific-Breakpoints-1"></a>
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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
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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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</p>
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<dl compact="compact">
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<dd><a name="index-breakpoints-and-threads"></a>
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<a name="index-thread-breakpoints"></a>
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<a name="index-break-_2026-thread-thread_002did"></a>
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</dd>
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<dt><code>break <var>location</var> thread <var>thread-id</var></code></dt>
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<dt><code>break <var>location</var> thread <var>thread-id</var> if …</code></dt>
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<dd><p><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>
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<p>Use the qualifier ‘<samp>thread <var>thread-id</var></samp>’ with a breakpoint command
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to specify that you only want <small>GDB</small> 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 <small>GDB</small>, shown
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in the first column of the ‘<samp>info threads</samp>’ display.
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</p>
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<p>If you do not specify ‘<samp>thread <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>
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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>thread <var>thread-id</var></samp>’ before or
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after the breakpoint condition, like this:
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</p>
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<div class="smallexample">
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<pre class="smallexample">(gdb) break frik.c:13 thread 28 if bartab > lim
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</pre></div>
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</dd>
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</dl>
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<p>Thread-specific breakpoints are automatically deleted when
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<small>GDB</small> detects the corresponding thread is no longer in the
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thread list. For example:
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</p>
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<div class="smallexample">
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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></div>
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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
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Process</a>), or if <small>GDB</small> 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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<small>GDB</small> 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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</p>
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<hr>
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<div class="header">
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<p>
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Next: <a href="Interrupted-System-Calls.html#Interrupted-System-Calls" accesskey="n" rel="next">Interrupted System Calls</a>, Previous: <a href="Background-Execution.html#Background-Execution" accesskey="p" rel="prev">Background Execution</a>, Up: <a href="Thread-Stops.html#Thread-Stops" accesskey="u" rel="up">Thread Stops</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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</body>
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</html>
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