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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 V1.75.2" /><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" title="Verbose Terminate Handler"><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>
If you are having difficulty with uncaught exceptions and want a
little bit of help debugging the causes of the core dumps, you can
make use of a GNU extension, the verbose terminate handler.
</p><pre class="programlisting">
#include <exception>
int main()
{
std::set_terminate(__gnu_cxx::__verbose_terminate_handler);
...
throw <em class="replaceable"><code>anything</code></em>;
}
</pre><p>
The <code class="function">__verbose_terminate_handler</code> function
obtains the name of the current exception, attempts to demangle
it, and prints it to stderr. If the exception is derived from
<code class="classname">exception</code> then the output from
<code class="function">what()</code> will be included.
</p><p>
Any replacement termination function is required to kill the
program without returning; this one calls abort.
</p><p>
For example:
</p><pre class="programlisting">
#include <exception>
#include <stdexcept>
struct argument_error : public std::runtime_error
{
argument_error(const std::string& s): std::runtime_error(s) { }
};
int main(int argc)
{
std::set_terminate(__gnu_cxx::__verbose_terminate_handler);
if (argc > 5)
throw argument_error(<span class="quote">“<span class="quote">argc is greater than 5!</span>”</span>);
else
throw argc;
}
</pre><p>
With the verbose terminate handler active, this gives:
</p><pre class="screen">
<code class="computeroutput">
% ./a.out
terminate called after throwing a `int'
Aborted
% ./a.out f f f f f f f f f f f
terminate called after throwing an instance of `argument_error'
what(): argc is greater than 5!
Aborted
</code>
</pre><p>
The 'Aborted' line comes from the call to
<code class="function">abort()</code>, of course.
</p><p>
This is the default termination handler; nothing need be done to
use it. To go back to the previous <span class="quote">“<span class="quote">silent death</span>”</span>
method, simply include <code class="filename">exception</code> and
<code class="filename">cstdlib</code>, and call
</p><pre class="programlisting">
std::set_terminate(std::abort);
</pre><p>
After this, all calls to <code class="function">terminate</code> will use
<code class="function">abort</code> as the terminate handler.
</p><p>
Note: the verbose terminate handler will attempt to write to
stderr. If your application closes stderr or redirects it to an
inappropriate location,
<code class="function">__verbose_terminate_handler</code> will behave in
an unspecified manner.
</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.
Diagnostics
</td></tr></table></div></body></html>
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