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317 lines
14 KiB
HTML
317 lines
14 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>Inferiors and Programs (Debugging with GDB)</title>
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<meta name="description" content="Inferiors and Programs (Debugging with GDB)">
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<meta name="keywords" content="Inferiors and Programs (Debugging with GDB)">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content="makeinfo">
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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="Running.html#Running" rel="up" title="Running">
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<link href="Threads.html#Threads" rel="next" title="Threads">
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<link href="Kill-Process.html#Kill-Process" rel="prev" title="Kill Process">
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</head>
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<body lang="en">
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<a name="Inferiors-and-Programs"></a>
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<div class="header">
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<p>
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Next: <a href="Threads.html#Threads" accesskey="n" rel="next">Threads</a>, Previous: <a href="Kill-Process.html#Kill-Process" accesskey="p" rel="prev">Kill Process</a>, Up: <a href="Running.html#Running" accesskey="u" rel="up">Running</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="Debugging-Multiple-Inferiors-and-Programs"></a>
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<h3 class="section">4.9 Debugging Multiple Inferiors and Programs</h3>
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<p><small>GDB</small> lets you run and debug multiple programs in a single
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session. In addition, <small>GDB</small> on some systems may let you run
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several programs simultaneously (otherwise you have to exit from one
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before starting another). In the most general case, you can have
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multiple threads of execution in each of multiple processes, launched
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from multiple executables.
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</p>
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<a name="index-inferior"></a>
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<p><small>GDB</small> represents the state of each program execution with an
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object called an <em>inferior</em>. An inferior typically corresponds to
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a process, but is more general and applies also to targets that do not
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have processes. Inferiors may be created before a process runs, and
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may be retained after a process exits. Inferiors have unique
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identifiers that are different from process ids. Usually each
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inferior will also have its own distinct address space, although some
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embedded targets may have several inferiors running in different parts
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of a single address space. Each inferior may in turn have multiple
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threads running in it.
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</p>
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<p>To find out what inferiors exist at any moment, use <code>info inferiors</code><!-- /@w -->:
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</p>
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<dl compact="compact">
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<dd><a name="index-info-inferiors-_005b-id_2026-_005d"></a>
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</dd>
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<dt><code>info inferiors</code></dt>
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<dd><p>Print a list of all inferiors currently being managed by <small>GDB</small>.
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By default all inferiors are printed, but the argument <var>id</var>…
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– a space separated list of inferior numbers – can be used to limit
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the display to just the requested inferiors.
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</p>
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<p><small>GDB</small> displays for each inferior (in this order):
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</p>
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<ol>
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<li> the inferior number assigned by <small>GDB</small>
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</li><li> the target system’s inferior identifier
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</li><li> the name of the executable the inferior is running.
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</li></ol>
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<p>An asterisk ‘<samp>*</samp>’ preceding the <small>GDB</small> inferior number
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indicates the current inferior.
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</p>
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<p>For example,
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</p></dd>
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</dl>
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<div class="smallexample">
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<pre class="smallexample">(gdb) info inferiors
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Num Description Executable
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2 process 2307 hello
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* 1 process 3401 goodbye
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</pre></div>
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<p>To switch focus between inferiors, use the <code>inferior</code> command:
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</p>
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<dl compact="compact">
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<dd><a name="index-inferior-infno"></a>
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</dd>
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<dt><code>inferior <var>infno</var></code></dt>
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<dd><p>Make inferior number <var>infno</var> the current inferior. The argument
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<var>infno</var> is the inferior number assigned by <small>GDB</small>, as shown
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in the first field of the ‘<samp>info inferiors</samp>’ display.
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</p></dd>
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</dl>
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<a name="index-_0024_005finferior_002c-convenience-variable"></a>
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<p>The debugger convenience variable ‘<samp>$_inferior</samp>’ contains the
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number of the current inferior. You may find this useful in writing
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breakpoint conditional expressions, command scripts, and so forth.
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See <a href="Convenience-Vars.html#Convenience-Vars">Convenience Variables</a>, for general
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information on convenience variables.
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</p>
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<p>You can get multiple executables into a debugging session via the
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<code>add-inferior</code> and <code><span class="nolinebreak">clone-inferior</span></code><!-- /@w --> commands. On some
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systems <small>GDB</small> can add inferiors to the debug session
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automatically by following calls to <code>fork</code> and <code>exec</code>. To
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remove inferiors from the debugging session use the
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<code><span class="nolinebreak">remove-inferiors</span></code><!-- /@w --> command.
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</p>
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<dl compact="compact">
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<dd><a name="index-add_002dinferior"></a>
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</dd>
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<dt><code>add-inferior [ -copies <var>n</var> ] [ -exec <var>executable</var> ]</code></dt>
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<dd><p>Adds <var>n</var> inferiors to be run using <var>executable</var> as the
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executable; <var>n</var> defaults to 1. If no executable is specified,
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the inferiors begins empty, with no program. You can still assign or
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change the program assigned to the inferior at any time by using the
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<code>file</code> command with the executable name as its argument.
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</p>
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<a name="index-clone_002dinferior"></a>
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</dd>
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<dt><code>clone-inferior [ -copies <var>n</var> ] [ <var>infno</var> ]</code></dt>
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<dd><p>Adds <var>n</var> inferiors ready to execute the same program as inferior
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<var>infno</var>; <var>n</var> defaults to 1, and <var>infno</var> defaults to the
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number of the current inferior. This is a convenient command when you
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want to run another instance of the inferior you are debugging.
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</p>
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<div class="smallexample">
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<pre class="smallexample">(gdb) info inferiors
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Num Description Executable
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* 1 process 29964 helloworld
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(gdb) clone-inferior
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Added inferior 2.
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1 inferiors added.
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(gdb) info inferiors
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Num Description Executable
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2 <null> helloworld
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* 1 process 29964 helloworld
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</pre></div>
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<p>You can now simply switch focus to inferior 2 and run it.
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</p>
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<a name="index-remove_002dinferiors"></a>
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</dd>
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<dt><code>remove-inferiors <var>infno</var>…</code></dt>
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<dd><p>Removes the inferior or inferiors <var>infno</var>…. It is not
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possible to remove an inferior that is running with this command. For
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those, use the <code>kill</code> or <code>detach</code> command first.
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</p>
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</dd>
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</dl>
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<p>To quit debugging one of the running inferiors that is not the current
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inferior, you can either detach from it by using the <code>detach inferior</code><!-- /@w --> command (allowing it to run independently), or kill it
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using the <code>kill inferiors</code><!-- /@w --> command:
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</p>
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<dl compact="compact">
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<dd><a name="index-detach-inferiors-infno_2026"></a>
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</dd>
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<dt><code>detach inferior <var>infno</var>…</code></dt>
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<dd><p>Detach from the inferior or inferiors identified by <small>GDB</small>
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inferior number(s) <var>infno</var>…. Note that the inferior’s entry
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still stays on the list of inferiors shown by <code>info inferiors</code>,
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but its Description will show ‘<samp><null></samp>’.
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</p>
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<a name="index-kill-inferiors-infno_2026"></a>
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</dd>
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<dt><code>kill inferiors <var>infno</var>…</code></dt>
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<dd><p>Kill the inferior or inferiors identified by <small>GDB</small> inferior
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number(s) <var>infno</var>…. Note that the inferior’s entry still
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stays on the list of inferiors shown by <code>info inferiors</code>, but its
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Description will show ‘<samp><null></samp>’.
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</p></dd>
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</dl>
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<p>After the successful completion of a command such as <code>detach</code>,
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<code>detach inferiors</code>, <code>kill</code> or <code>kill inferiors</code>, or after
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a normal process exit, the inferior is still valid and listed with
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<code>info inferiors</code>, ready to be restarted.
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</p>
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<p>To be notified when inferiors are started or exit under <small>GDB</small>’s
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control use <code>set print <span class="nolinebreak">inferior-events</span></code><!-- /@w -->:
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</p>
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<dl compact="compact">
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<dd><a name="index-set-print-inferior_002devents"></a>
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<a name="index-print-messages-on-inferior-start-and-exit"></a>
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</dd>
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<dt><code>set print inferior-events</code></dt>
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<dt><code>set print inferior-events on</code></dt>
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<dt><code>set print inferior-events off</code></dt>
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<dd><p>The <code>set print inferior-events</code> command allows you to enable or
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disable printing of messages when <small>GDB</small> notices that new
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inferiors have started or that inferiors have exited or have been
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detached. By default, these messages will not be printed.
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</p>
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<a name="index-show-print-inferior_002devents"></a>
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</dd>
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<dt><code>show print inferior-events</code></dt>
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<dd><p>Show whether messages will be printed when <small>GDB</small> detects that
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inferiors have started, exited or have been detached.
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</p></dd>
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</dl>
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<p>Many commands will work the same with multiple programs as with a
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single program: e.g., <code>print myglobal</code> will simply display the
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value of <code>myglobal</code> in the current inferior.
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</p>
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<p>Occasionaly, when debugging <small>GDB</small> itself, it may be useful to
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get more info about the relationship of inferiors, programs, address
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spaces in a debug session. You can do that with the <code>maint info <span class="nolinebreak">program-spaces</span></code><!-- /@w --> command.
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</p>
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<dl compact="compact">
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<dd><a name="index-maint-info-program_002dspaces"></a>
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</dd>
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<dt><code>maint info program-spaces</code></dt>
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<dd><p>Print a list of all program spaces currently being managed by
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<small>GDB</small>.
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</p>
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<p><small>GDB</small> displays for each program space (in this order):
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</p>
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<ol>
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<li> the program space number assigned by <small>GDB</small>
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</li><li> the name of the executable loaded into the program space, with e.g.,
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the <code>file</code> command.
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</li></ol>
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<p>An asterisk ‘<samp>*</samp>’ preceding the <small>GDB</small> program space number
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indicates the current program space.
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</p>
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<p>In addition, below each program space line, <small>GDB</small> prints extra
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information that isn’t suitable to display in tabular form. For
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example, the list of inferiors bound to the program space.
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</p>
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<div class="smallexample">
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<pre class="smallexample">(gdb) maint info program-spaces
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Id Executable
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* 1 hello
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2 goodbye
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Bound inferiors: ID 1 (process 21561)
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</pre></div>
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<p>Here we can see that no inferior is running the program <code>hello</code>,
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while <code>process 21561</code> is running the program <code>goodbye</code>. On
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some targets, it is possible that multiple inferiors are bound to the
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same program space. The most common example is that of debugging both
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the parent and child processes of a <code>vfork</code> call. For example,
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</p>
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<div class="smallexample">
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<pre class="smallexample">(gdb) maint info program-spaces
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Id Executable
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* 1 vfork-test
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Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
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</pre></div>
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<p>Here, both inferior 2 and inferior 1 are running in the same program
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space as a result of inferior 1 having executed a <code>vfork</code> call.
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</p></dd>
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</dl>
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|
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<hr>
|
||
|
|
<div class="header">
|
||
|
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<p>
|
||
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