diff options
Diffstat (limited to 'libstdc++-v3/doc/html/manual/termination.html')
| -rw-r--r-- | libstdc++-v3/doc/html/manual/termination.html | 124 |
1 files changed, 124 insertions, 0 deletions
diff --git a/libstdc++-v3/doc/html/manual/termination.html b/libstdc++-v3/doc/html/manual/termination.html new file mode 100644 index 000000000..cc5235943 --- /dev/null +++ b/libstdc++-v3/doc/html/manual/termination.html @@ -0,0 +1,124 @@ +<?xml version="1.0" encoding="UTF-8" standalone="no"?> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd"> +<html xmlns="http://www.w3.org/1999/xhtml"><head><title>Termination</title><meta name="generator" content="DocBook XSL-NS Stylesheets V1.76.1"/><meta name="keywords" content=" ISO C++ , library "/><link rel="home" href="../spine.html" title="The GNU C++ Library"/><link rel="up" href="support.html" title="Chapter 4. Support"/><link rel="prev" href="dynamic_memory.html" title="Dynamic Memory"/><link rel="next" href="diagnostics.html" title="Chapter 5. Diagnostics"/></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Termination</th></tr><tr><td align="left"><a accesskey="p" href="dynamic_memory.html">Prev</a> </td><th width="60%" align="center">Chapter 4. + Support + +</th><td align="right"> <a accesskey="n" href="diagnostics.html">Next</a></td></tr></table><hr/></div><div class="section" title="Termination"><div class="titlepage"><div><div><h2 class="title"><a id="std.support.termination"/>Termination</h2></div></div></div><div class="section" title="Termination Handlers"><div class="titlepage"><div><div><h3 class="title"><a id="support.termination.handlers"/>Termination Handlers</h3></div></div></div><p> + Not many changes here to <code class="filename">cstdlib</code>. You should note that the + <code class="function">abort()</code> function does not call the + destructors of automatic nor static objects, so if you're + depending on those to do cleanup, it isn't going to happen. + (The functions registered with <code class="function">atexit()</code> + don't get called either, so you can forget about that + possibility, too.) + </p><p> + The good old <code class="function">exit()</code> function can be a bit + funky, too, until you look closer. Basically, three points to + remember are: + </p><div class="orderedlist"><ol class="orderedlist"><li class="listitem"><p> + Static objects are destroyed in reverse order of their creation. + </p></li><li class="listitem"><p> + Functions registered with <code class="function">atexit()</code> are called in + reverse order of registration, once per registration call. + (This isn't actually new.) + </p></li><li class="listitem"><p> + The previous two actions are <span class="quote">“<span class="quote">interleaved,</span>”</span> that is, + given this pseudocode: + </p><pre class="programlisting"> + extern "C or C++" void f1 (void); + extern "C or C++" void f2 (void); + + static Thing obj1; + atexit(f1); + static Thing obj2; + atexit(f2); +</pre><p> + then at a call of <code class="function">exit()</code>, + <code class="varname">f2</code> will be called, then + <code class="varname">obj2</code> will be destroyed, then + <code class="varname">f1</code> will be called, and finally + <code class="varname">obj1</code> will be destroyed. If + <code class="varname">f1</code> or <code class="varname">f2</code> allow an + exception to propagate out of them, Bad Things happen. + </p></li></ol></div><p> + Note also that <code class="function">atexit()</code> is only required to store 32 + functions, and the compiler/library might already be using some of + those slots. If you think you may run out, we recommend using + the <code class="function">xatexit</code>/<code class="function">xexit</code> combination from <code class="literal">libiberty</code>, which has no such limit. + </p></div><div class="section" title="Verbose Terminate Handler"><div class="titlepage"><div><div><h3 class="title"><a id="support.termination.verbose"/>Verbose Terminate Handler</h3></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><div class="navfooter"><hr/><table width="100%" summary="Navigation footer"><tr><td align="left"><a accesskey="p" href="dynamic_memory.html">Prev</a> </td><td align="center"><a accesskey="u" href="support.html">Up</a></td><td align="right"> <a accesskey="n" href="diagnostics.html">Next</a></td></tr><tr><td align="left" valign="top">Dynamic Memory </td><td align="center"><a accesskey="h" href="../spine.html">Home</a></td><td align="right" valign="top"> Chapter 5. + Diagnostics + +</td></tr></table></div></body></html> |