229 lines
11 KiB
HTML
229 lines
11 KiB
HTML
|
<html lang="en">
|
||
|
|
<head>
|
||
|
|
<title>Character Sets - 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="Data.html#Data" title="Data">
|
||
|
|
<link rel="prev" href="Core-File-Generation.html#Core-File-Generation" title="Core File Generation">
|
||
|
|
<link rel="next" href="Caching-Target-Data.html#Caching-Target-Data" title="Caching Target Data">
|
||
|
|
<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="Character-Sets"></a>
|
||
|
|
<p>
|
||
|
|
Next: <a rel="next" accesskey="n" href="Caching-Target-Data.html#Caching-Target-Data">Caching Target Data</a>,
|
||
|
|
Previous: <a rel="previous" accesskey="p" href="Core-File-Generation.html#Core-File-Generation">Core File Generation</a>,
|
||
|
|
Up: <a rel="up" accesskey="u" href="Data.html#Data">Data</a>
|
||
|
|
<hr>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<h3 class="section">10.20 Character Sets</h3>
|
||
|
|
|
||
|
|
<p><a name="index-character-sets-803"></a><a name="index-charset-804"></a><a name="index-translating-between-character-sets-805"></a><a name="index-host-character-set-806"></a><a name="index-target-character-set-807"></a>
|
||
|
|
If the program you are debugging uses a different character set to
|
||
|
|
represent characters and strings than the one <span class="sc">gdb</span> uses itself,
|
||
|
|
<span class="sc">gdb</span> can automatically translate between the character sets for
|
||
|
|
you. The character set <span class="sc">gdb</span> uses we call the <dfn>host
|
||
|
|
character set</dfn>; the one the inferior program uses we call the
|
||
|
|
<dfn>target character set</dfn>.
|
||
|
|
|
||
|
|
<p>For example, if you are running <span class="sc">gdb</span> on a <span class="sc">gnu</span>/Linux system, which
|
||
|
|
uses the ISO Latin 1 character set, but you are using <span class="sc">gdb</span>'s
|
||
|
|
remote protocol (see <a href="Remote-Debugging.html#Remote-Debugging">Remote Debugging</a>) to debug a program
|
||
|
|
running on an IBM mainframe, which uses the <span class="sc">ebcdic</span> character set,
|
||
|
|
then the host character set is Latin-1, and the target character set is
|
||
|
|
<span class="sc">ebcdic</span>. If you give <span class="sc">gdb</span> the command <code>set
|
||
|
|
target-charset EBCDIC-US</code>, then <span class="sc">gdb</span> translates between
|
||
|
|
<span class="sc">ebcdic</span> and Latin 1 as you print character or string values, or use
|
||
|
|
character and string literals in expressions.
|
||
|
|
|
||
|
|
<p><span class="sc">gdb</span> has no way to automatically recognize which character set
|
||
|
|
the inferior program uses; you must tell it, using the <code>set
|
||
|
|
target-charset</code> command, described below.
|
||
|
|
|
||
|
|
<p>Here are the commands for controlling <span class="sc">gdb</span>'s character set
|
||
|
|
support:
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt><code>set target-charset </code><var>charset</var><dd><a name="index-set-target_002dcharset-808"></a>Set the current target character set to <var>charset</var>. To display the
|
||
|
|
list of supported target character sets, type
|
||
|
|
<kbd>set target-charset <TAB><TAB><!-- /@w --></kbd>.
|
||
|
|
|
||
|
|
<br><dt><code>set host-charset </code><var>charset</var><dd><a name="index-set-host_002dcharset-809"></a>Set the current host character set to <var>charset</var>.
|
||
|
|
|
||
|
|
<p>By default, <span class="sc">gdb</span> uses a host character set appropriate to the
|
||
|
|
system it is running on; you can override that default using the
|
||
|
|
<code>set host-charset</code> command. On some systems, <span class="sc">gdb</span> cannot
|
||
|
|
automatically determine the appropriate host character set. In this
|
||
|
|
case, <span class="sc">gdb</span> uses ‘<samp><span class="samp">UTF-8</span></samp>’.
|
||
|
|
|
||
|
|
<p><span class="sc">gdb</span> can only use certain character sets as its host character
|
||
|
|
set. If you type <kbd>set host-charset <TAB><TAB><!-- /@w --></kbd>,
|
||
|
|
<span class="sc">gdb</span> will list the host character sets it supports.
|
||
|
|
|
||
|
|
<br><dt><code>set charset </code><var>charset</var><dd><a name="index-set-charset-810"></a>Set the current host and target character sets to <var>charset</var>. As
|
||
|
|
above, if you type <kbd>set charset <TAB><TAB><!-- /@w --></kbd>,
|
||
|
|
<span class="sc">gdb</span> will list the names of the character sets that can be used
|
||
|
|
for both host and target.
|
||
|
|
|
||
|
|
<br><dt><code>show charset</code><dd><a name="index-show-charset-811"></a>Show the names of the current host and target character sets.
|
||
|
|
|
||
|
|
<br><dt><code>show host-charset</code><dd><a name="index-show-host_002dcharset-812"></a>Show the name of the current host character set.
|
||
|
|
|
||
|
|
<br><dt><code>show target-charset</code><dd><a name="index-show-target_002dcharset-813"></a>Show the name of the current target character set.
|
||
|
|
|
||
|
|
<br><dt><code>set target-wide-charset </code><var>charset</var><dd><a name="index-set-target_002dwide_002dcharset-814"></a>Set the current target's wide character set to <var>charset</var>. This is
|
||
|
|
the character set used by the target's <code>wchar_t</code> type. To
|
||
|
|
display the list of supported wide character sets, type
|
||
|
|
<kbd>set target-wide-charset <TAB><TAB><!-- /@w --></kbd>.
|
||
|
|
|
||
|
|
<br><dt><code>show target-wide-charset</code><dd><a name="index-show-target_002dwide_002dcharset-815"></a>Show the name of the current target's wide character set.
|
||
|
|
</dl>
|
||
|
|
|
||
|
|
<p>Here is an example of <span class="sc">gdb</span>'s character set support in action.
|
||
|
|
Assume that the following source code has been placed in the file
|
||
|
|
<samp><span class="file">charset-test.c</span></samp>:
|
||
|
|
|
||
|
|
<pre class="smallexample"> #include <stdio.h>
|
||
|
|
|
||
|
|
char ascii_hello[]
|
||
|
|
= {72, 101, 108, 108, 111, 44, 32, 119,
|
||
|
|
111, 114, 108, 100, 33, 10, 0};
|
||
|
|
char ibm1047_hello[]
|
||
|
|
= {200, 133, 147, 147, 150, 107, 64, 166,
|
||
|
|
150, 153, 147, 132, 90, 37, 0};
|
||
|
|
|
||
|
|
main ()
|
||
|
|
{
|
||
|
|
printf ("Hello, world!\n");
|
||
|
|
}
|
||
|
|
</pre>
|
||
|
|
<p>In this program, <code>ascii_hello</code> and <code>ibm1047_hello</code> are arrays
|
||
|
|
containing the string ‘<samp><span class="samp">Hello, world!</span></samp>’ followed by a newline,
|
||
|
|
encoded in the <span class="sc">ascii</span> and <span class="sc">ibm1047</span> character sets.
|
||
|
|
|
||
|
|
<p>We compile the program, and invoke the debugger on it:
|
||
|
|
|
||
|
|
<pre class="smallexample"> $ gcc -g charset-test.c -o charset-test
|
||
|
|
$ gdb -nw charset-test
|
||
|
|
GNU gdb 2001-12-19-cvs
|
||
|
|
Copyright 2001 Free Software Foundation, Inc.
|
||
|
|
...
|
||
|
|
(gdb)
|
||
|
|
</pre>
|
||
|
|
<p>We can use the <code>show charset</code> command to see what character sets
|
||
|
|
<span class="sc">gdb</span> is currently using to interpret and display characters and
|
||
|
|
strings:
|
||
|
|
|
||
|
|
<pre class="smallexample"> (gdb) show charset
|
||
|
|
The current host and target character set is `ISO-8859-1'.
|
||
|
|
(gdb)
|
||
|
|
</pre>
|
||
|
|
<p>For the sake of printing this manual, let's use <span class="sc">ascii</span> as our
|
||
|
|
initial character set:
|
||
|
|
<pre class="smallexample"> (gdb) set charset ASCII
|
||
|
|
(gdb) show charset
|
||
|
|
The current host and target character set is `ASCII'.
|
||
|
|
(gdb)
|
||
|
|
</pre>
|
||
|
|
<p>Let's assume that <span class="sc">ascii</span> is indeed the correct character set for our
|
||
|
|
host system — in other words, let's assume that if <span class="sc">gdb</span> prints
|
||
|
|
characters using the <span class="sc">ascii</span> character set, our terminal will display
|
||
|
|
them properly. Since our current target character set is also
|
||
|
|
<span class="sc">ascii</span>, the contents of <code>ascii_hello</code> print legibly:
|
||
|
|
|
||
|
|
<pre class="smallexample"> (gdb) print ascii_hello
|
||
|
|
$1 = 0x401698 "Hello, world!\n"
|
||
|
|
(gdb) print ascii_hello[0]
|
||
|
|
$2 = 72 'H'
|
||
|
|
(gdb)
|
||
|
|
</pre>
|
||
|
|
<p><span class="sc">gdb</span> uses the target character set for character and string
|
||
|
|
literals you use in expressions:
|
||
|
|
|
||
|
|
<pre class="smallexample"> (gdb) print '+'
|
||
|
|
$3 = 43 '+'
|
||
|
|
(gdb)
|
||
|
|
</pre>
|
||
|
|
<p>The <span class="sc">ascii</span> character set uses the number 43 to encode the ‘<samp><span class="samp">+</span></samp>’
|
||
|
|
character.
|
||
|
|
|
||
|
|
<p><span class="sc">gdb</span> relies on the user to tell it which character set the
|
||
|
|
target program uses. If we print <code>ibm1047_hello</code> while our target
|
||
|
|
character set is still <span class="sc">ascii</span>, we get jibberish:
|
||
|
|
|
||
|
|
<pre class="smallexample"> (gdb) print ibm1047_hello
|
||
|
|
$4 = 0x4016a8 "\310\205\223\223\226k@\246\226\231\223\204Z%"
|
||
|
|
(gdb) print ibm1047_hello[0]
|
||
|
|
$5 = 200 '\310'
|
||
|
|
(gdb)
|
||
|
|
</pre>
|
||
|
|
<p>If we invoke the <code>set target-charset</code> followed by <TAB><TAB>,
|
||
|
|
<span class="sc">gdb</span> tells us the character sets it supports:
|
||
|
|
|
||
|
|
<pre class="smallexample"> (gdb) set target-charset
|
||
|
|
ASCII EBCDIC-US IBM1047 ISO-8859-1
|
||
|
|
(gdb) set target-charset
|
||
|
|
</pre>
|
||
|
|
<p>We can select <span class="sc">ibm1047</span> as our target character set, and examine the
|
||
|
|
program's strings again. Now the <span class="sc">ascii</span> string is wrong, but
|
||
|
|
<span class="sc">gdb</span> translates the contents of <code>ibm1047_hello</code> from the
|
||
|
|
target character set, <span class="sc">ibm1047</span>, to the host character set,
|
||
|
|
<span class="sc">ascii</span>, and they display correctly:
|
||
|
|
|
||
|
|
<pre class="smallexample"> (gdb) set target-charset IBM1047
|
||
|
|
(gdb) show charset
|
||
|
|
The current host character set is `ASCII'.
|
||
|
|
The current target character set is `IBM1047'.
|
||
|
|
(gdb) print ascii_hello
|
||
|
|
$6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
|
||
|
|
(gdb) print ascii_hello[0]
|
||
|
|
$7 = 72 '\110'
|
||
|
|
(gdb) print ibm1047_hello
|
||
|
|
$8 = 0x4016a8 "Hello, world!\n"
|
||
|
|
(gdb) print ibm1047_hello[0]
|
||
|
|
$9 = 200 'H'
|
||
|
|
(gdb)
|
||
|
|
</pre>
|
||
|
|
<p>As above, <span class="sc">gdb</span> uses the target character set for character and
|
||
|
|
string literals you use in expressions:
|
||
|
|
|
||
|
|
<pre class="smallexample"> (gdb) print '+'
|
||
|
|
$10 = 78 '+'
|
||
|
|
(gdb)
|
||
|
|
</pre>
|
||
|
|
<p>The <span class="sc">ibm1047</span> character set uses the number 78 to encode the ‘<samp><span class="samp">+</span></samp>’
|
||
|
|
character.
|
||
|
|
|
||
|
|
</body></html>
|
||
|
|
|