huangmeng
/
asj_pe_project


			
							123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127
							<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<!-- Copyright (C) 1988-2020 Free Software Foundation, Inc.

Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with the
Invariant Sections being "Free Software" and "Free Software Needs
Free Documentation", with the Front-Cover Texts being "A GNU Manual,"
and with the Back-Cover Texts as in (a) below.

(a) The FSF's Back-Cover Text is: "You are free to copy and modify
this GNU Manual.  Buying copies from GNU Press supports the FSF in
developing GNU and promoting software freedom." -->
<!-- Created by GNU Texinfo 5.1, http://www.gnu.org/software/texinfo/ -->
<head>
<title>Debugging with GDB: Tracepoints</title>

<meta name="description" content="Debugging with GDB: Tracepoints">
<meta name="keywords" content="Debugging with GDB: Tracepoints">
<meta name="resource-type" content="document">
<meta name="distribution" content="global">
<meta name="Generator" content="makeinfo">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<link href="index.html#Top" rel="start" title="Top">
<link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
<link href="index.html#Top" rel="up" title="Top">
<link href="Set-Tracepoints.html#Set-Tracepoints" rel="next" title="Set Tracepoints">
<link href="Macros.html#Macros" rel="previous" title="Macros">
<style type="text/css">
<!--
a.summary-letter {text-decoration: none}
blockquote.smallquotation {font-size: smaller}
div.display {margin-left: 3.2em}
div.example {margin-left: 3.2em}
div.indentedblock {margin-left: 3.2em}
div.lisp {margin-left: 3.2em}
div.smalldisplay {margin-left: 3.2em}
div.smallexample {margin-left: 3.2em}
div.smallindentedblock {margin-left: 3.2em; font-size: smaller}
div.smalllisp {margin-left: 3.2em}
kbd {font-style:oblique}
pre.display {font-family: inherit}
pre.format {font-family: inherit}
pre.menu-comment {font-family: serif}
pre.menu-preformatted {font-family: serif}
pre.smalldisplay {font-family: inherit; font-size: smaller}
pre.smallexample {font-size: smaller}
pre.smallformat {font-family: inherit; font-size: smaller}
pre.smalllisp {font-size: smaller}
span.nocodebreak {white-space:nowrap}
span.nolinebreak {white-space:nowrap}
span.roman {font-family:serif; font-weight:normal}
span.sansserif {font-family:sans-serif; font-weight:normal}
ul.no-bullet {list-style: none}
-->
</style>


</head>

<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
<a name="Tracepoints"></a>
<div class="header">
<p>
Next: <a href="Overlays.html#Overlays" accesskey="n" rel="next">Overlays</a>, Previous: <a href="Macros.html#Macros" accesskey="p" rel="previous">Macros</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</a> &nbsp; [<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>
</div>
<hr>
<a name="Tracepoints-1"></a>
<h2 class="chapter">13 Tracepoints</h2>

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

<hr>
<div class="header">
<p>
Next: <a href="Overlays.html#Overlays" accesskey="n" rel="next">Overlays</a>, Previous: <a href="Macros.html#Macros" accesskey="p" rel="previous">Macros</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</a> &nbsp; [<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>
</div>


</body>
</html>