huangmeng
/
asj_pe_project


			
							123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255256257258259260
							<!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: Define</title>

<meta name="description" content="Debugging with GDB: Define">
<meta name="keywords" content="Debugging with GDB: Define">
<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="Sequences.html#Sequences" rel="up" title="Sequences">
<link href="Hooks.html#Hooks" rel="next" title="Hooks">
<link href="Sequences.html#Sequences" rel="previous" title="Sequences">
<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="Define"></a>
<div class="header">
<p>
Next: <a href="Hooks.html#Hooks" accesskey="n" rel="next">Hooks</a>, Up: <a href="Sequences.html#Sequences" accesskey="u" rel="up">Sequences</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="User_002ddefined-Commands"></a>
<h4 class="subsection">23.1.1 User-defined Commands</h4>

<a name="index-user_002ddefined-command"></a>
<a name="index-arguments_002c-to-user_002ddefined-commands"></a>
<p>A <em>user-defined command</em> is a sequence of <small>GDB</small> commands to
which you assign a new name as a command.  This is done with the
<code>define</code> command.  User commands may accept an unlimited number of arguments
separated by whitespace.  Arguments are accessed within the user command
via <code>$arg0&hellip;$argN</code>.  A trivial example:
</p>
<div class="smallexample">
<pre class="smallexample">define adder
  print $arg0 + $arg1 + $arg2
end
</pre></div>

<p>To execute the command use:
</p>
<div class="smallexample">
<pre class="smallexample">adder 1 2 3
</pre></div>

<p>This defines the command <code>adder</code>, which prints the sum of
its three arguments.  Note the arguments are text substitutions, so they may
reference variables, use complex expressions, or even perform inferior
functions calls.
</p>
<a name="index-argument-count-in-user_002ddefined-commands"></a>
<a name="index-how-many-arguments-_0028user_002ddefined-commands_0029"></a>
<p>In addition, <code>$argc</code> may be used to find out how many arguments have
been passed.
</p>
<div class="smallexample">
<pre class="smallexample">define adder
  if $argc == 2
    print $arg0 + $arg1
  end
  if $argc == 3
    print $arg0 + $arg1 + $arg2
  end
end
</pre></div>

<p>Combining with the <code>eval</code> command (see <a href="Output.html#eval">eval</a>) makes it easier
to process a variable number of arguments:
</p>
<div class="smallexample">
<pre class="smallexample">define adder
  set $i = 0
  set $sum = 0
  while $i &lt; $argc
    eval &quot;set $sum = $sum + $arg%d&quot;, $i
    set $i = $i + 1
  end
  print $sum
end
</pre></div>

<dl compact="compact">
<dd>
<a name="index-define"></a>
</dd>
<dt><code>define <var>commandname</var></code></dt>
<dd><p>Define a command named <var>commandname</var>.  If there is already a command
by that name, you are asked to confirm that you want to redefine it.
The argument <var>commandname</var> may be a bare command name consisting of letters,
numbers, dashes, dots, and underscores.  It may also start with any
predefined or user-defined prefix command.
For example, &lsquo;<samp>define target my-target</samp>&rsquo; creates
a user-defined &lsquo;<samp>target my-target</samp>&rsquo; command.
</p>
<p>The definition of the command is made up of other <small>GDB</small> command lines,
which are given following the <code>define</code> command.  The end of these
commands is marked by a line containing <code>end</code>.
</p>
<a name="index-document"></a>
<a name="index-end-_0028user_002ddefined-commands_0029"></a>
</dd>
<dt><code>document <var>commandname</var></code></dt>
<dd><p>Document the user-defined command <var>commandname</var>, so that it can be
accessed by <code>help</code>.  The command <var>commandname</var> must already be
defined.  This command reads lines of documentation just as <code>define</code>
reads the lines of the command definition, ending with <code>end</code>.
After the <code>document</code> command is finished, <code>help</code> on command
<var>commandname</var> displays the documentation you have written.
</p>
<p>You may use the <code>document</code> command again to change the
documentation of a command.  Redefining the command with <code>define</code>
does not change the documentation.
</p>
<a name="index-define_002dprefix"></a>
</dd>
<dt><code>define-prefix <var>commandname</var></code></dt>
<dd><p>Define or mark the command <var>commandname</var> as a user-defined prefix
command.  Once marked, <var>commandname</var> can be used as prefix command
by the  <code>define</code> command.
Note that <code>define-prefix</code> can be used with a not yet defined
<var>commandname</var>.  In such a case, <var>commandname</var> is defined as
an empty user-defined command.
In case you redefine a command that was marked as a user-defined
prefix command, the subcommands of the redefined command are kept
(and <small>GDB</small> indicates so to the user).
</p>
<p>Example:
</p><div class="example">
<pre class="example">(gdb) define-prefix abc
(gdb) define-prefix abc def
(gdb) define abc def
Type commands for definition of &quot;abc def&quot;.
End with a line saying just &quot;end&quot;.
&gt;echo command initial def\n
&gt;end
(gdb) define abc def ghi
Type commands for definition of &quot;abc def ghi&quot;.
End with a line saying just &quot;end&quot;.
&gt;echo command ghi\n
&gt;end
(gdb) define abc def
Keeping subcommands of prefix command &quot;def&quot;.
Redefine command &quot;def&quot;? (y or n) y
Type commands for definition of &quot;abc def&quot;.
End with a line saying just &quot;end&quot;.
&gt;echo command def\n
&gt;end
(gdb) abc def ghi
command ghi
(gdb) abc def
command def
(gdb)
</pre></div>

<a name="index-dont_002drepeat-1"></a>
<a name="index-don_0027t-repeat-command"></a>
</dd>
<dt><code>dont-repeat</code></dt>
<dd><p>Used inside a user-defined command, this tells <small>GDB</small> that this
command should not be repeated when the user hits <tt class="key">RET</tt>
(see <a href="Command-Syntax.html#Command-Syntax">repeat last command</a>).
</p>
<a name="index-help-user_002ddefined"></a>
</dd>
<dt><code>help user-defined</code></dt>
<dd><p>List all user-defined commands and all python commands defined in class
COMMAND_USER.  The first line of the documentation or docstring is
included (if any).
</p>
<a name="index-show-user"></a>
</dd>
<dt><code>show user</code></dt>
<dt><code>show user <var>commandname</var></code></dt>
<dd><p>Display the <small>GDB</small> commands used to define <var>commandname</var> (but
not its documentation).  If no <var>commandname</var> is given, display the
definitions for all user-defined commands.
This does not work for user-defined python commands.
</p>
<a name="index-infinite-recursion-in-user_002ddefined-commands"></a>
<a name="index-show-max_002duser_002dcall_002ddepth"></a>
<a name="index-set-max_002duser_002dcall_002ddepth"></a>
</dd>
<dt><code>show max-user-call-depth</code></dt>
<dt><code>set max-user-call-depth</code></dt>
<dd><p>The value of <code>max-user-call-depth</code> controls how many recursion
levels are allowed in user-defined commands before <small>GDB</small> suspects an
infinite recursion and aborts the command.
This does not apply to user-defined python commands.
</p></dd>
</dl>

<p>In addition to the above commands, user-defined commands frequently
use control flow commands, described in <a href="Command-Files.html#Command-Files">Command Files</a>.
</p>
<p>When user-defined commands are executed, the
commands of the definition are not printed.  An error in any command
stops execution of the user-defined command.
</p>
<p>If used interactively, commands that would ask for confirmation proceed
without asking when used inside a user-defined command.  Many <small>GDB</small>
commands that normally print messages to say what they are doing omit the
messages when used in a user-defined command.
</p>
<hr>
<div class="header">
<p>
Next: <a href="Hooks.html#Hooks" accesskey="n" rel="next">Hooks</a>, Up: <a href="Sequences.html#Sequences" accesskey="u" rel="up">Sequences</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>