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| <title>Debugging with GDB: Core File Generation</title> |
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| <a name="Core-File-Generation"></a> |
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| Next: <a href="Character-Sets.html#Character-Sets" accesskey="n" rel="next">Character Sets</a>, Previous: <a href="Dump_002fRestore-Files.html#Dump_002fRestore-Files" accesskey="p" rel="prev">Dump/Restore Files</a>, Up: <a href="Data.html#Data" accesskey="u" rel="up">Data</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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| <hr> |
| <a name="How-to-Produce-a-Core-File-from-Your-Program"></a> |
| <h3 class="section">10.19 How to Produce a Core File from Your Program</h3> |
| <a name="index-dump-core-from-inferior"></a> |
| |
| <p>A <em>core file</em> or <em>core dump</em> is a file that records the memory |
| image of a running process and its process status (register values |
| etc.). Its primary use is post-mortem debugging of a program that |
| crashed while it ran outside a debugger. A program that crashes |
| automatically produces a core file, unless this feature is disabled by |
| the user. See <a href="Files.html#Files">Files</a>, for information on invoking <small>GDB</small> in |
| the post-mortem debugging mode. |
| </p> |
| <p>Occasionally, you may wish to produce a core file of the program you |
| are debugging in order to preserve a snapshot of its state. |
| <small>GDB</small> has a special command for that. |
| </p> |
| <dl compact="compact"> |
| <dd><a name="index-gcore"></a> |
| <a name="index-generate_002dcore_002dfile"></a> |
| </dd> |
| <dt><code>generate-core-file [<var>file</var>]</code></dt> |
| <dt><code>gcore [<var>file</var>]</code></dt> |
| <dd><p>Produce a core dump of the inferior process. The optional argument |
| <var>file</var> specifies the file name where to put the core dump. If not |
| specified, the file name defaults to <samp>core.<var>pid</var></samp>, where |
| <var>pid</var> is the inferior process ID. |
| </p> |
| <p>Note that this command is implemented only for some systems (as of |
| this writing, <small>GNU</small>/Linux, FreeBSD, Solaris, and S390). |
| </p> |
| <p>On <small>GNU</small>/Linux, this command can take into account the value of the |
| file <samp>/proc/<var>pid</var>/coredump_filter</samp> when generating the core |
| dump (see <a href="#set-use_002dcoredump_002dfilter">set use-coredump-filter</a>). |
| </p> |
| <a name="index-set-use_002dcoredump_002dfilter"></a> |
| <a name="set-use_002dcoredump_002dfilter"></a></dd> |
| <dt><code>set use-coredump-filter on</code></dt> |
| <dt><code>set use-coredump-filter off</code></dt> |
| <dd><p>Enable or disable the use of the file |
| <samp>/proc/<var>pid</var>/coredump_filter</samp> when generating core dump |
| files. This file is used by the Linux kernel to decide what types of |
| memory mappings will be dumped or ignored when generating a core dump |
| file. <var>pid</var> is the process ID of a currently running process. |
| </p> |
| <p>To make use of this feature, you have to write in the |
| <samp>/proc/<var>pid</var>/coredump_filter</samp> file a value, in hexadecimal, |
| which is a bit mask representing the memory mapping types. If a bit |
| is set in the bit mask, then the memory mappings of the corresponding |
| types will be dumped; otherwise, they will be ignored. This |
| configuration is inherited by child processes. For more information |
| about the bits that can be set in the |
| <samp>/proc/<var>pid</var>/coredump_filter</samp> file, please refer to the |
| manpage of <code>core(5)</code>. |
| </p> |
| <p>By default, this option is <code>on</code>. If this option is turned |
| <code>off</code>, <small>GDB</small> does not read the <samp>coredump_filter</samp> file |
| and instead uses the same default value as the Linux kernel in order |
| to decide which pages will be dumped in the core dump file. This |
| value is currently <code>0x33</code>, which means that bits <code>0</code> |
| (anonymous private mappings), <code>1</code> (anonymous shared mappings), |
| <code>4</code> (ELF headers) and <code>5</code> (private huge pages) are active. |
| This will cause these memory mappings to be dumped automatically. |
| </p></dd> |
| </dl> |
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| Next: <a href="Character-Sets.html#Character-Sets" accesskey="n" rel="next">Character Sets</a>, Previous: <a href="Dump_002fRestore-Files.html#Dump_002fRestore-Files" accesskey="p" rel="prev">Dump/Restore Files</a>, Up: <a href="Data.html#Data" accesskey="u" rel="up">Data</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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