118 lines
6.5 KiB
HTML
118 lines
6.5 KiB
HTML
<html lang="en">
|
|
<head>
|
|
<title>Observer Mode - Debugging with GDB</title>
|
|
<meta http-equiv="Content-Type" content="text/html">
|
|
<meta name="description" content="Debugging with GDB">
|
|
<meta name="generator" content="makeinfo 4.13">
|
|
<link title="Top" rel="start" href="index.html#Top">
|
|
<link rel="up" href="Thread-Stops.html#Thread-Stops" title="Thread Stops">
|
|
<link rel="prev" href="Interrupted-System-Calls.html#Interrupted-System-Calls" title="Interrupted System Calls">
|
|
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
|
|
<!--
|
|
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.''
|
|
-->
|
|
<meta http-equiv="Content-Style-Type" content="text/css">
|
|
<style type="text/css"><!--
|
|
pre.display { font-family:inherit }
|
|
pre.format { font-family:inherit }
|
|
pre.smalldisplay { font-family:inherit; font-size:smaller }
|
|
pre.smallformat { font-family:inherit; font-size:smaller }
|
|
pre.smallexample { font-size:smaller }
|
|
pre.smalllisp { font-size:smaller }
|
|
span.sc { font-variant:small-caps }
|
|
span.roman { font-family:serif; font-weight:normal; }
|
|
span.sansserif { font-family:sans-serif; font-weight:normal; }
|
|
--></style>
|
|
</head>
|
|
<body>
|
|
<div class="node">
|
|
<a name="Observer-Mode"></a>
|
|
<p>
|
|
Previous: <a rel="previous" accesskey="p" href="Interrupted-System-Calls.html#Interrupted-System-Calls">Interrupted System Calls</a>,
|
|
Up: <a rel="up" accesskey="u" href="Thread-Stops.html#Thread-Stops">Thread Stops</a>
|
|
<hr>
|
|
</div>
|
|
|
|
<h4 class="subsection">5.5.6 Observer Mode</h4>
|
|
|
|
<p>If you want to build on non-stop mode and observe program behavior
|
|
without any chance of disruption by <span class="sc">gdb</span>, you can set
|
|
variables to disable all of the debugger's attempts to modify state,
|
|
whether by writing memory, inserting breakpoints, etc. These operate
|
|
at a low level, intercepting operations from all commands.
|
|
|
|
<p>When all of these are set to <code>off</code>, then <span class="sc">gdb</span> is said to
|
|
be <dfn>observer mode</dfn>. As a convenience, the variable
|
|
<code>observer</code> can be set to disable these, plus enable non-stop
|
|
mode.
|
|
|
|
<p>Note that <span class="sc">gdb</span> will not prevent you from making nonsensical
|
|
combinations of these settings. For instance, if you have enabled
|
|
<code>may-insert-breakpoints</code> but disabled <code>may-write-memory</code>,
|
|
then breakpoints that work by writing trap instructions into the code
|
|
stream will still not be able to be placed.
|
|
|
|
|
|
<a name="index-observer-434"></a>
|
|
<dl><dt><code>set observer on</code><dt><code>set observer off</code><dd>When set to <code>on</code>, this disables all the permission variables
|
|
below (except for <code>insert-fast-tracepoints</code>), plus enables
|
|
non-stop debugging. Setting this to <code>off</code> switches back to
|
|
normal debugging, though remaining in non-stop mode.
|
|
|
|
<br><dt><code>show observer</code><dd>Show whether observer mode is on or off.
|
|
|
|
<p><a name="index-may_002dwrite_002dregisters-435"></a><br><dt><code>set may-write-registers on</code><dt><code>set may-write-registers off</code><dd>This controls whether <span class="sc">gdb</span> will attempt to alter the values of
|
|
registers, such as with assignment expressions in <code>print</code>, or the
|
|
<code>jump</code> command. It defaults to <code>on</code>.
|
|
|
|
<br><dt><code>show may-write-registers</code><dd>Show the current permission to write registers.
|
|
|
|
<p><a name="index-may_002dwrite_002dmemory-436"></a><br><dt><code>set may-write-memory on</code><dt><code>set may-write-memory off</code><dd>This controls whether <span class="sc">gdb</span> will attempt to alter the contents
|
|
of memory, such as with assignment expressions in <code>print</code>. It
|
|
defaults to <code>on</code>.
|
|
|
|
<br><dt><code>show may-write-memory</code><dd>Show the current permission to write memory.
|
|
|
|
<p><a name="index-may_002dinsert_002dbreakpoints-437"></a><br><dt><code>set may-insert-breakpoints on</code><dt><code>set may-insert-breakpoints off</code><dd>This controls whether <span class="sc">gdb</span> will attempt to insert breakpoints.
|
|
This affects all breakpoints, including internal breakpoints defined
|
|
by <span class="sc">gdb</span>. It defaults to <code>on</code>.
|
|
|
|
<br><dt><code>show may-insert-breakpoints</code><dd>Show the current permission to insert breakpoints.
|
|
|
|
<p><a name="index-may_002dinsert_002dtracepoints-438"></a><br><dt><code>set may-insert-tracepoints on</code><dt><code>set may-insert-tracepoints off</code><dd>This controls whether <span class="sc">gdb</span> will attempt to insert (regular)
|
|
tracepoints at the beginning of a tracing experiment. It affects only
|
|
non-fast tracepoints, fast tracepoints being under the control of
|
|
<code>may-insert-fast-tracepoints</code>. It defaults to <code>on</code>.
|
|
|
|
<br><dt><code>show may-insert-tracepoints</code><dd>Show the current permission to insert tracepoints.
|
|
|
|
<p><a name="index-may_002dinsert_002dfast_002dtracepoints-439"></a><br><dt><code>set may-insert-fast-tracepoints on</code><dt><code>set may-insert-fast-tracepoints off</code><dd>This controls whether <span class="sc">gdb</span> will attempt to insert fast
|
|
tracepoints at the beginning of a tracing experiment. It affects only
|
|
fast tracepoints, regular (non-fast) tracepoints being under the
|
|
control of <code>may-insert-tracepoints</code>. It defaults to <code>on</code>.
|
|
|
|
<br><dt><code>show may-insert-fast-tracepoints</code><dd>Show the current permission to insert fast tracepoints.
|
|
|
|
<p><a name="index-may_002dinterrupt-440"></a><br><dt><code>set may-interrupt on</code><dt><code>set may-interrupt off</code><dd>This controls whether <span class="sc">gdb</span> will attempt to interrupt or stop
|
|
program execution. When this variable is <code>off</code>, the
|
|
<code>interrupt</code> command will have no effect, nor will
|
|
<kbd>Ctrl-c</kbd>. It defaults to <code>on</code>.
|
|
|
|
<br><dt><code>show may-interrupt</code><dd>Show the current permission to interrupt or stop the program.
|
|
|
|
</dl>
|
|
|
|
</body></html>
|
|
|