You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
167 lines
7.5 KiB
HTML
167 lines
7.5 KiB
HTML
4 years ago
|
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
|
||
|
|
<html>
|
||
|
|
<!-- Copyright (C) 1988-2019 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 6.4, http://www.gnu.org/software/texinfo/ -->
|
||
|
|
<head>
|
||
|
|
<title>Break Commands (Debugging with GDB)</title>
|
||
|
|
|
||
|
|
<meta name="description" content="Break Commands (Debugging with GDB)">
|
||
|
|
<meta name="keywords" content="Break Commands (Debugging with GDB)">
|
||
|
|
<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="Breakpoints.html#Breakpoints" rel="up" title="Breakpoints">
|
||
|
|
<link href="Dynamic-Printf.html#Dynamic-Printf" rel="next" title="Dynamic Printf">
|
||
|
|
<link href="Conditions.html#Conditions" rel="prev" title="Conditions">
|
||
|
|
<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="Break-Commands"></a>
|
||
|
|
<div class="header">
|
||
|
|
<p>
|
||
|
|
Next: <a href="Dynamic-Printf.html#Dynamic-Printf" accesskey="n" rel="next">Dynamic Printf</a>, Previous: <a href="Conditions.html#Conditions" accesskey="p" rel="prev">Conditions</a>, Up: <a href="Breakpoints.html#Breakpoints" accesskey="u" rel="up">Breakpoints</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>
|
||
|
|
</div>
|
||
|
|
<hr>
|
||
|
|
<a name="Breakpoint-Command-Lists"></a>
|
||
|
|
<h4 class="subsection">5.1.7 Breakpoint Command Lists</h4>
|
||
|
|
|
||
|
|
<a name="index-breakpoint-commands"></a>
|
||
|
|
<p>You can give any breakpoint (or watchpoint or catchpoint) a series of
|
||
|
|
commands to execute when your program stops due to that breakpoint. For
|
||
|
|
example, you might want to print the values of certain expressions, or
|
||
|
|
enable other breakpoints.
|
||
|
|
</p>
|
||
|
|
<dl compact="compact">
|
||
|
|
<dd><a name="index-commands"></a>
|
||
|
|
<a name="index-end-_0028breakpoint-commands_0029"></a>
|
||
|
|
</dd>
|
||
|
|
<dt><code>commands <span class="roman">[</span><var>list</var>…<span class="roman">]</span></code></dt>
|
||
|
|
<dt><code>… <var>command-list</var> …</code></dt>
|
||
|
|
<dt><code>end</code></dt>
|
||
|
|
<dd><p>Specify a list of commands for the given breakpoints. The commands
|
||
|
|
themselves appear on the following lines. Type a line containing just
|
||
|
|
<code>end</code> to terminate the commands.
|
||
|
|
</p>
|
||
|
|
<p>To remove all commands from a breakpoint, type <code>commands</code> and
|
||
|
|
follow it immediately with <code>end</code>; that is, give no commands.
|
||
|
|
</p>
|
||
|
|
<p>With no argument, <code>commands</code> refers to the last breakpoint,
|
||
|
|
watchpoint, or catchpoint set (not to the breakpoint most recently
|
||
|
|
encountered). If the most recent breakpoints were set with a single
|
||
|
|
command, then the <code>commands</code> will apply to all the breakpoints
|
||
|
|
set by that command. This applies to breakpoints set by
|
||
|
|
<code>rbreak</code>, and also applies when a single <code>break</code> command
|
||
|
|
creates multiple breakpoints (see <a href="Ambiguous-Expressions.html#Ambiguous-Expressions">Ambiguous
|
||
|
|
Expressions</a>).
|
||
|
|
</p></dd>
|
||
|
|
</dl>
|
||
|
|
|
||
|
|
<p>Pressing <tt class="key">RET</tt> as a means of repeating the last <small>GDB</small> command is
|
||
|
|
disabled within a <var>command-list</var>.
|
||
|
|
</p>
|
||
|
|
<p>You can use breakpoint commands to start your program up again. Simply
|
||
|
|
use the <code>continue</code> command, or <code>step</code>, or any other command
|
||
|
|
that resumes execution.
|
||
|
|
</p>
|
||
|
|
<p>Any other commands in the command list, after a command that resumes
|
||
|
|
execution, are ignored. This is because any time you resume execution
|
||
|
|
(even with a simple <code>next</code> or <code>step</code>), you may encounter
|
||
|
|
another breakpoint—which could have its own command list, leading to
|
||
|
|
ambiguities about which list to execute.
|
||
|
|
</p>
|
||
|
|
<a name="index-silent"></a>
|
||
|
|
<p>If the first command you specify in a command list is <code>silent</code>, the
|
||
|
|
usual message about stopping at a breakpoint is not printed. This may
|
||
|
|
be desirable for breakpoints that are to print a specific message and
|
||
|
|
then continue. If none of the remaining commands print anything, you
|
||
|
|
see no sign that the breakpoint was reached. <code>silent</code> is
|
||
|
|
meaningful only at the beginning of a breakpoint command list.
|
||
|
|
</p>
|
||
|
|
<p>The commands <code>echo</code>, <code>output</code>, and <code>printf</code> allow you to
|
||
|
|
print precisely controlled output, and are often useful in silent
|
||
|
|
breakpoints. See <a href="Output.html#Output">Commands for Controlled Output</a>.
|
||
|
|
</p>
|
||
|
|
<p>For example, here is how you could use breakpoint commands to print the
|
||
|
|
value of <code>x</code> at entry to <code>foo</code> whenever <code>x</code> is positive.
|
||
|
|
</p>
|
||
|
|
<div class="smallexample">
|
||
|
|
<pre class="smallexample">break foo if x>0
|
||
|
|
commands
|
||
|
|
silent
|
||
|
|
printf "x is %d\n",x
|
||
|
|
cont
|
||
|
|
end
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<p>One application for breakpoint commands is to compensate for one bug so
|
||
|
|
you can test for another. Put a breakpoint just after the erroneous line
|
||
|
|
of code, give it a condition to detect the case in which something
|
||
|
|
erroneous has been done, and give it commands to assign correct values
|
||
|
|
to any variables that need them. End with the <code>continue</code> command
|
||
|
|
so that your program does not stop, and start with the <code>silent</code>
|
||
|
|
command so that no output is produced. Here is an example:
|
||
|
|
</p>
|
||
|
|
<div class="smallexample">
|
||
|
|
<pre class="smallexample">break 403
|
||
|
|
commands
|
||
|
|
silent
|
||
|
|
set x = y + 4
|
||
|
|
cont
|
||
|
|
end
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<hr>
|
||
|
|
<div class="header">
|
||
|
|
<p>
|
||
|
|
Next: <a href="Dynamic-Printf.html#Dynamic-Printf" accesskey="n" rel="next">Dynamic Printf</a>, Previous: <a href="Conditions.html#Conditions" accesskey="p" rel="prev">Conditions</a>, Up: <a href="Breakpoints.html#Breakpoints" accesskey="u" rel="up">Breakpoints</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>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
</body>
|
||
|
|
</html>
|