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127 lines
6.5 KiB
HTML
127 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>Tracepoints (Debugging with GDB)</title>
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<meta name="description" content="Tracepoints (Debugging with GDB)">
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<meta name="keywords" content="Tracepoints (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="index.html#Top" rel="up" title="Top">
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<link href="Set-Tracepoints.html#Set-Tracepoints" rel="next" title="Set Tracepoints">
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<link href="Macros.html#Macros" rel="prev" title="Macros">
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</style>
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</head>
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<body lang="en">
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<a name="Tracepoints"></a>
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<div class="header">
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<p>
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Next: <a href="Overlays.html#Overlays" accesskey="n" rel="next">Overlays</a>, Previous: <a href="Macros.html#Macros" accesskey="p" rel="prev">Macros</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</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="Tracepoints-1"></a>
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<h2 class="chapter">13 Tracepoints</h2>
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<a name="index-tracepoints"></a>
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<p>In some applications, it is not feasible for the debugger to interrupt
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the program’s execution long enough for the developer to learn
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anything helpful about its behavior. If the program’s correctness
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depends on its real-time behavior, delays introduced by a debugger
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might cause the program to change its behavior drastically, or perhaps
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fail, even when the code itself is correct. It is useful to be able
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to observe the program’s behavior without interrupting it.
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</p>
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<p>Using <small>GDB</small>’s <code>trace</code> and <code>collect</code> commands, you can
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specify locations in the program, called <em>tracepoints</em>, and
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arbitrary expressions to evaluate when those tracepoints are reached.
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Later, using the <code>tfind</code> command, you can examine the values
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those expressions had when the program hit the tracepoints. The
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expressions may also denote objects in memory—structures or arrays,
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for example—whose values <small>GDB</small> should record; while visiting
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a particular tracepoint, you may inspect those objects as if they were
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in memory at that moment. However, because <small>GDB</small> records these
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values without interacting with you, it can do so quickly and
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unobtrusively, hopefully not disturbing the program’s behavior.
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</p>
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<p>The tracepoint facility is currently available only for remote
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targets. See <a href="Targets.html#Targets">Targets</a>. In addition, your remote target must know
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how to collect trace data. This functionality is implemented in the
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remote stub; however, none of the stubs distributed with <small>GDB</small>
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support tracepoints as of this writing. The format of the remote
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packets used to implement tracepoints are described in <a href="Tracepoint-Packets.html#Tracepoint-Packets">Tracepoint Packets</a>.
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</p>
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<p>It is also possible to get trace data from a file, in a manner reminiscent
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of corefiles; you specify the filename, and use <code>tfind</code> to search
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through the file. See <a href="Trace-Files.html#Trace-Files">Trace Files</a>, for more details.
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</p>
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<p>This chapter describes the tracepoint commands and features.
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</p>
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<table class="menu" border="0" cellspacing="0">
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<tr><td align="left" valign="top">• <a href="Set-Tracepoints.html#Set-Tracepoints" accesskey="1">Set Tracepoints</a>:</td><td> </td><td align="left" valign="top">
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</td></tr>
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<tr><td align="left" valign="top">• <a href="Analyze-Collected-Data.html#Analyze-Collected-Data" accesskey="2">Analyze Collected Data</a>:</td><td> </td><td align="left" valign="top">
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</td></tr>
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<tr><td align="left" valign="top">• <a href="Tracepoint-Variables.html#Tracepoint-Variables" accesskey="3">Tracepoint Variables</a>:</td><td> </td><td align="left" valign="top">
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</td></tr>
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<tr><td align="left" valign="top">• <a href="Trace-Files.html#Trace-Files" accesskey="4">Trace Files</a>:</td><td> </td><td align="left" valign="top">
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</td></tr>
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</table>
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<hr>
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<div class="header">
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<p>
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Next: <a href="Overlays.html#Overlays" accesskey="n" rel="next">Overlays</a>, Previous: <a href="Macros.html#Macros" accesskey="p" rel="prev">Macros</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</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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