227 lines
12 KiB
HTML
227 lines
12 KiB
HTML
<html lang="en">
|
|
<head>
|
|
<title>Completion - 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="Commands.html#Commands" title="Commands">
|
|
<link rel="prev" href="Command-Syntax.html#Command-Syntax" title="Command Syntax">
|
|
<link rel="next" href="Help.html#Help" title="Help">
|
|
<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="Completion"></a>
|
|
<p>
|
|
Next: <a rel="next" accesskey="n" href="Help.html#Help">Help</a>,
|
|
Previous: <a rel="previous" accesskey="p" href="Command-Syntax.html#Command-Syntax">Command Syntax</a>,
|
|
Up: <a rel="up" accesskey="u" href="Commands.html#Commands">Commands</a>
|
|
<hr>
|
|
</div>
|
|
|
|
<h3 class="section">3.2 Command Completion</h3>
|
|
|
|
<p><a name="index-completion-84"></a><a name="index-word-completion-85"></a><span class="sc">gdb</span> can fill in the rest of a word in a command for you, if there is
|
|
only one possibility; it can also show you what the valid possibilities
|
|
are for the next word in a command, at any time. This works for <span class="sc">gdb</span>
|
|
commands, <span class="sc">gdb</span> subcommands, and the names of symbols in your program.
|
|
|
|
<p>Press the <TAB> key whenever you want <span class="sc">gdb</span> to fill out the rest
|
|
of a word. If there is only one possibility, <span class="sc">gdb</span> fills in the
|
|
word, and waits for you to finish the command (or press <RET> to
|
|
enter it). For example, if you type
|
|
|
|
<!-- FIXME "@key" does not distinguish its argument sufficiently to permit -->
|
|
<!-- complete accuracy in these examples; space introduced for clarity. -->
|
|
<!-- If texinfo enhancements make it unnecessary, it would be nice to -->
|
|
<!-- replace " @key" by "@key" in the following... -->
|
|
<pre class="smallexample"> (gdb) info bre <TAB>
|
|
</pre>
|
|
<p class="noindent"><span class="sc">gdb</span> fills in the rest of the word ‘<samp><span class="samp">breakpoints</span></samp>’, since that is
|
|
the only <code>info</code> subcommand beginning with ‘<samp><span class="samp">bre</span></samp>’:
|
|
|
|
<pre class="smallexample"> (gdb) info breakpoints
|
|
</pre>
|
|
<p class="noindent">You can either press <RET> at this point, to run the <code>info
|
|
breakpoints</code> command, or backspace and enter something else, if
|
|
‘<samp><span class="samp">breakpoints</span></samp>’ does not look like the command you expected. (If you
|
|
were sure you wanted <code>info breakpoints</code> in the first place, you
|
|
might as well just type <RET> immediately after ‘<samp><span class="samp">info bre</span></samp>’,
|
|
to exploit command abbreviations rather than command completion).
|
|
|
|
<p>If there is more than one possibility for the next word when you press
|
|
<TAB>, <span class="sc">gdb</span> sounds a bell. You can either supply more
|
|
characters and try again, or just press <TAB> a second time;
|
|
<span class="sc">gdb</span> displays all the possible completions for that word. For
|
|
example, you might want to set a breakpoint on a subroutine whose name
|
|
begins with ‘<samp><span class="samp">make_</span></samp>’, but when you type <kbd>b make_<TAB></kbd> <span class="sc">gdb</span>
|
|
just sounds the bell. Typing <TAB> again displays all the
|
|
function names in your program that begin with those characters, for
|
|
example:
|
|
|
|
<pre class="smallexample"> (gdb) b make_ <TAB>
|
|
<br><span class="sc">gdb</span> sounds bell; press <TAB> again, to see:<br>
|
|
make_a_section_from_file make_environ
|
|
make_abs_section make_function_type
|
|
make_blockvector make_pointer_type
|
|
make_cleanup make_reference_type
|
|
make_command make_symbol_completion_list
|
|
(gdb) b make_
|
|
</pre>
|
|
<p class="noindent">After displaying the available possibilities, <span class="sc">gdb</span> copies your
|
|
partial input (‘<samp><span class="samp">b make_</span></samp>’ in the example) so you can finish the
|
|
command.
|
|
|
|
<p>If you just want to see the list of alternatives in the first place, you
|
|
can press <kbd>M-?</kbd> rather than pressing <TAB> twice. <kbd>M-?</kbd>
|
|
means <kbd><META> ?</kbd>. You can type this either by holding down a
|
|
key designated as the <META> shift on your keyboard (if there is
|
|
one) while typing <kbd>?</kbd>, or as <ESC> followed by <kbd>?</kbd>.
|
|
|
|
<p>If the number of possible completions is large, <span class="sc">gdb</span> will
|
|
print as much of the list as it has collected, as well as a message
|
|
indicating that the list may be truncated.
|
|
|
|
<pre class="smallexample"> (gdb) b m<TAB><TAB>
|
|
main
|
|
<... the rest of the possible completions ...>
|
|
*** List may be truncated, max-completions reached. ***
|
|
(gdb) b m
|
|
</pre>
|
|
<p class="noindent">This behavior can be controlled with the following commands:
|
|
|
|
|
|
<a name="index-set-max_002dcompletions-86"></a>
|
|
<dl><dt><code>set max-completions </code><var>limit</var><dt><code>set max-completions unlimited</code><dd>Set the maximum number of completion candidates. <span class="sc">gdb</span> will
|
|
stop looking for more completions once it collects this many candidates.
|
|
This is useful when completing on things like function names as collecting
|
|
all the possible candidates can be time consuming.
|
|
The default value is 200. A value of zero disables tab-completion.
|
|
Note that setting either no limit or a very large limit can make
|
|
completion slow.
|
|
<a name="index-show-max_002dcompletions-87"></a><br><dt><code>show max-completions</code><dd>Show the maximum number of candidates that <span class="sc">gdb</span> will collect and show
|
|
during completion.
|
|
</dl>
|
|
|
|
<p><a name="index-quotes-in-commands-88"></a><a name="index-completion-of-quoted-strings-89"></a>Sometimes the string you need, while logically a “word”, may contain
|
|
parentheses or other characters that <span class="sc">gdb</span> normally excludes from
|
|
its notion of a word. To permit word completion to work in this
|
|
situation, you may enclose words in <code>'</code> (single quote marks) in
|
|
<span class="sc">gdb</span> commands.
|
|
|
|
<p>A likely situation where you might need this is in typing an
|
|
expression that involves a C<tt>++</tt> symbol name with template
|
|
parameters. This is because when completing expressions, GDB treats
|
|
the ‘<samp><span class="samp"><</span></samp>’ character as word delimiter, assuming that it's the
|
|
less-than comparison operator (see <a href="C-Operators.html#C-Operators">C and C<tt>++</tt> Operators</a>).
|
|
|
|
<p>For example, when you want to call a C<tt>++</tt> template function
|
|
interactively using the <code>print</code> or <code>call</code> commands, you may
|
|
need to distinguish whether you mean the version of <code>name</code> that
|
|
was specialized for <code>int</code>, <code>name<int>()</code>, or the version
|
|
that was specialized for <code>float</code>, <code>name<float>()</code>. To use
|
|
the word-completion facilities in this situation, type a single quote
|
|
<code>'</code> at the beginning of the function name. This alerts
|
|
<span class="sc">gdb</span> that it may need to consider more information than usual
|
|
when you press <TAB> or <kbd>M-?</kbd> to request word completion:
|
|
|
|
<pre class="smallexample"> (gdb) p 'func< <kbd>M-?</kbd>
|
|
func<int>() func<float>()
|
|
(gdb) p 'func<
|
|
</pre>
|
|
<p>When setting breakpoints however (see <a href="Specify-Location.html#Specify-Location">Specify Location</a>), you don't
|
|
usually need to type a quote before the function name, because
|
|
<span class="sc">gdb</span> understands that you want to set a breakpoint on a
|
|
function:
|
|
|
|
<pre class="smallexample"> (gdb) b func< <kbd>M-?</kbd>
|
|
func<int>() func<float>()
|
|
(gdb) b func<
|
|
</pre>
|
|
<p>This is true even in the case of typing the name of C<tt>++</tt> overloaded
|
|
functions (multiple definitions of the same function, distinguished by
|
|
argument type). For example, when you want to set a breakpoint you
|
|
don't need to distinguish whether you mean the version of <code>name</code>
|
|
that takes an <code>int</code> parameter, <code>name(int)</code>, or the version
|
|
that takes a <code>float</code> parameter, <code>name(float)</code>.
|
|
|
|
<pre class="smallexample"> (gdb) b bubble( <kbd>M-?</kbd>
|
|
bubble(int) bubble(double)
|
|
(gdb) b bubble(dou <kbd>M-?</kbd>
|
|
bubble(double)
|
|
</pre>
|
|
<p>See <a href="quoting-names.html#quoting-names">quoting names</a> for a description of other scenarios that
|
|
require quoting.
|
|
|
|
<p>For more information about overloaded functions, see <a href="C-Plus-Plus-Expressions.html#C-Plus-Plus-Expressions">C<tt>++</tt> Expressions</a>. You can use the command <code>set
|
|
overload-resolution off</code> to disable overload resolution;
|
|
see <a href="Debugging-C-Plus-Plus.html#Debugging-C-Plus-Plus"><span class="sc">gdb</span> Features for C<tt>++</tt></a>.
|
|
|
|
<p><a name="index-completion-of-structure-field-names-90"></a><a name="index-structure-field-name-completion-91"></a><a name="index-completion-of-union-field-names-92"></a><a name="index-union-field-name-completion-93"></a>When completing in an expression which looks up a field in a
|
|
structure, <span class="sc">gdb</span> also tries<a rel="footnote" href="#fn-1" name="fnd-1"><sup>1</sup></a> to
|
|
limit completions to the field names available in the type of the
|
|
left-hand-side:
|
|
|
|
<pre class="smallexample"> (gdb) p gdb_stdout.<kbd>M-?</kbd>
|
|
magic to_fputs to_rewind
|
|
to_data to_isatty to_write
|
|
to_delete to_put to_write_async_safe
|
|
to_flush to_read
|
|
</pre>
|
|
<p class="noindent">This is because the <code>gdb_stdout</code> is a variable of the type
|
|
<code>struct ui_file</code> that is defined in <span class="sc">gdb</span> sources as
|
|
follows:
|
|
|
|
<pre class="smallexample"> struct ui_file
|
|
{
|
|
int *magic;
|
|
ui_file_flush_ftype *to_flush;
|
|
ui_file_write_ftype *to_write;
|
|
ui_file_write_async_safe_ftype *to_write_async_safe;
|
|
ui_file_fputs_ftype *to_fputs;
|
|
ui_file_read_ftype *to_read;
|
|
ui_file_delete_ftype *to_delete;
|
|
ui_file_isatty_ftype *to_isatty;
|
|
ui_file_rewind_ftype *to_rewind;
|
|
ui_file_put_ftype *to_put;
|
|
void *to_data;
|
|
}
|
|
</pre>
|
|
<div class="footnote">
|
|
<hr>
|
|
<h4>Footnotes</h4><p class="footnote"><small>[<a name="fn-1" href="#fnd-1">1</a>]</small> The completer can be
|
|
confused by certain kinds of invalid expressions. Also, it only
|
|
examines the static type of the expression, not the dynamic type.</p>
|
|
|
|
<hr></div>
|
|
|
|
</body></html>
|
|
|