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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>Adding Data to Exceptions</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /><meta name="keywords" content=" ISO C++ , library " /><link rel="start" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="bk01pt03ch07.html" title="Chapter 7. Exceptions" /><link rel="prev" href="bk01pt03ch07.html" title="Chapter 7. Exceptions" /><link rel="next" href="bk01pt03ch07s03.html" title="Cancellation" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Adding Data to Exceptions</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="bk01pt03ch07.html">Prev</a> </td><th width="60%" align="center">Chapter 7. Exceptions</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt03ch07s03.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="manual.diagnostics.exceptions.data"></a>Adding Data to Exceptions</h2></div></div></div><p>
The standard exception classes carry with them a single string as
data (usually describing what went wrong or where the 'throw' took
place). It's good to remember that you can add your own data to
these exceptions when extending the hierarchy:
</p><pre class="programlisting">
struct My_Exception : public std::runtime_error
{
public:
My_Exception (const string& whatarg)
: std::runtime_error(whatarg), e(errno), id(GetDataBaseID()) { }
int errno_at_time_of_throw() const { return e; }
DBID id_of_thing_that_threw() const { return id; }
protected:
int e;
DBID id; // some user-defined type
};
</pre></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bk01pt03ch07.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="bk01pt03ch07.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01pt03ch07s03.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 7. Exceptions </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Cancellation</td></tr></table></div></body></html>
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