visus
/
toolchain-gcc-arm-embedded

<!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 6.5, http://www.gnu.org/software/texinfo/ -->
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>In-Process Agent (Debugging with GDB)</title>

<meta name="description" content="In-Process Agent (Debugging with GDB)">
<meta name="keywords" content="In-Process Agent (Debugging with GDB)">
<meta name="resource-type" content="document">
<meta name="distribution" content="global">
<meta name="Generator" content="makeinfo">
<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="In_002dProcess-Agent-Protocol.html#In_002dProcess-Agent-Protocol" rel="next" title="In-Process Agent Protocol">
<link href="Writing-JIT-Debug-Info-Readers.html#Writing-JIT-Debug-Info-Readers" rel="prev" title="Writing JIT Debug Info Readers">
<style type="text/css">
<!--
a.summary-letter {text-decoration: none}
blockquote.indentedblock {margin-right: 0em}
blockquote.smallindentedblock {margin-right: 0em; font-size: smaller}
blockquote.smallquotation {font-size: smaller}
div.display {margin-left: 3.2em}
div.example {margin-left: 3.2em}
div.lisp {margin-left: 3.2em}
div.smalldisplay {margin-left: 3.2em}
div.smallexample {margin-left: 3.2em}
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.nolinebreak {white-space: nowrap}
span.roman {font-family: initial; font-weight: normal}
span.sansserif {font-family: sans-serif; font-weight: normal}
ul.no-bullet {list-style: none}
-->
</style>


</head>

<body lang="en">
<a name="In_002dProcess-Agent"></a>
<div class="header">
<p>
Next: <a href="GDB-Bugs.html#GDB-Bugs" accesskey="n" rel="next">GDB Bugs</a>, Previous: <a href="JIT-Interface.html#JIT-Interface" accesskey="p" rel="prev">JIT Interface</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="In_002dProcess-Agent-1"></a>
<h2 class="chapter">30 In-Process Agent</h2>
<a name="index-debugging-agent"></a>
<p>The traditional debugging model is conceptually low-speed, but works fine,
because most bugs can be reproduced in debugging-mode execution.  However,
as multi-core or many-core processors are becoming mainstream, and
multi-threaded programs become more and more popular, there should be more
and more bugs that only manifest themselves at normal-mode execution, for
example, thread races, because debugger&rsquo;s interference with the program&rsquo;s
timing may conceal the bugs.  On the other hand, 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 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>Therefore, traditional debugging model is too intrusive to reproduce
some bugs.  In order to reduce the interference with the program, we can
reduce the number of operations performed by debugger.  The
<em>In-Process Agent</em>, a shared library, is running within the same
process with inferior, and is able to perform some debugging operations
itself.  As a result, debugger is only involved when necessary, and
performance of debugging can be improved accordingly.  Note that
interference with program can be reduced but can&rsquo;t be removed completely,
because the in-process agent will still stop or slow down the program.
</p>
<p>The in-process agent can interpret and execute Agent Expressions
(see <a href="Agent-Expressions.html#Agent-Expressions">Agent Expressions</a>) during performing debugging operations.  The
agent expressions can be used for different purposes, such as collecting
data in tracepoints, and condition evaluation in breakpoints.
</p>
<a name="Control-Agent"></a><p>You can control whether the in-process agent is used as an aid for
debugging with the following commands:
</p>
<dl compact="compact">
<dd><a name="index-set-agent-on"></a>
</dd>
<dt><code>set agent on</code></dt>
<dd><p>Causes the in-process agent to perform some operations on behalf of the
debugger.  Just which operations requested by the user will be done
by the in-process agent depends on the its capabilities.  For example,
if you request to evaluate breakpoint conditions in the in-process agent,
and the in-process agent has such capability as well, then breakpoint
conditions will be evaluated in the in-process agent.
</p>
<a name="index-set-agent-off"></a>
</dd>
<dt><code>set agent off</code></dt>
<dd><p>Disables execution of debugging operations by the in-process agent.  All
of the operations will be performed by <small>GDB</small>.
</p>
<a name="index-show-agent"></a>
</dd>
<dt><code>show agent</code></dt>
<dd><p>Display the current setting of execution of debugging operations by
the in-process agent.
</p></dd>
</dl>

<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top">&bull; <a href="In_002dProcess-Agent-Protocol.html#In_002dProcess-Agent-Protocol" accesskey="1">In-Process Agent Protocol</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
</table>

<hr>
<div class="header">
<p>
Next: <a href="GDB-Bugs.html#GDB-Bugs" accesskey="n" rel="next">GDB Bugs</a>, Previous: <a href="JIT-Interface.html#JIT-Interface" accesskey="p" rel="prev">JIT Interface</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>