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80 lines
4.6 KiB
HTML
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Verbose Terminate Handler</title><meta name="generator" content="DocBook XSL Stylesheets V1.74.3" /><meta name="keywords" content=" ISO C++ , library " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="termination.html" title="Chapter 6. Termination" /><link rel="prev" href="termination.html" title="Chapter 6. Termination" /><link rel="next" href="diagnostics.html" title="Part III. Diagnostics" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Verbose Terminate Handler</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="termination.html">Prev</a> </td><th width="60%" align="center">Chapter 6. Termination</th><td width="20%" align="right"> <a accesskey="n" href="diagnostics.html">Next</a></td></tr></table><hr /></div><div class="sect1" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="support.termination.verbose"></a>Verbose Terminate Handler</h2></div></div></div><p>
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If you are having difficulty with uncaught exceptions and want a
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little bit of help debugging the causes of the core dumps, you can
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make use of a GNU extension, the verbose terminate handler.
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</p><pre class="programlisting">
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#include <exception>
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int main()
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{
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std::set_terminate(__gnu_cxx::__verbose_terminate_handler);
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...
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throw <em class="replaceable"><code>anything</code></em>;
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}
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</pre><p>
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The <code class="function">__verbose_terminate_handler</code> function
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obtains the name of the current exception, attempts to demangle
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it, and prints it to stderr. If the exception is derived from
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<code class="classname">exception</code> then the output from
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<code class="function">what()</code> will be included.
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</p><p>
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Any replacement termination function is required to kill the
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program without returning; this one calls abort.
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</p><p>
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For example:
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</p><pre class="programlisting">
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#include <exception>
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#include <stdexcept>
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struct argument_error : public std::runtime_error
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{
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argument_error(const std::string& s): std::runtime_error(s) { }
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};
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int main(int argc)
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{
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std::set_terminate(__gnu_cxx::__verbose_terminate_handler);
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if (argc > 5)
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throw argument_error(“<span class="quote">argc is greater than 5!</span>”);
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else
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throw argc;
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}
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</pre><p>
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With the verbose terminate handler active, this gives:
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</p><pre class="screen">
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<code class="computeroutput">
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% ./a.out
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terminate called after throwing a `int'
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Aborted
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% ./a.out f f f f f f f f f f f
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terminate called after throwing an instance of `argument_error'
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what(): argc is greater than 5!
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Aborted
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</code>
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</pre><p>
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The 'Aborted' line comes from the call to
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<code class="function">abort()</code>, of course.
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</p><p>
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This is the default termination handler; nothing need be done to
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use it. To go back to the previous “<span class="quote">silent death</span>”
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method, simply include <code class="filename">exception</code> and
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<code class="filename">cstdlib</code>, and call
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</p><pre class="programlisting">
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std::set_terminate(std::abort);
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</pre><p>
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After this, all calls to <code class="function">terminate</code> will use
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<code class="function">abort</code> as the terminate handler.
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</p><p>
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Note: the verbose terminate handler will attempt to write to
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stderr. If your application closes stderr or redirects it to an
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inappropriate location,
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<code class="function">__verbose_terminate_handler</code> will behave in
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an unspecified manner.
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</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="termination.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="termination.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="diagnostics.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 6. Termination </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Part III.
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Diagnostics
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</td></tr></table></div></body></html>
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