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| <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. |
| |
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