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<b>Db::set_errcall</b>
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<b><pre>
#include <db_cxx.h>
<p>
void Db::set_errcall(void (*db_errcall_fcn)
(const DbEnv *dbenv, const char *errpfx, const char *msg));
</pre></b>
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<b>Description: Db::set_errcall</b>
When an error occurs in the Berkeley DB library, an exception is thrown or an
error return value is returned by the interface. In some cases,
however, the <b>errno</b> value may be insufficient to completely
describe the cause of the error, especially during initial application
debugging.
<p>The <a href="../api_cxx/env_set_errcall.html">DbEnv::set_errcall</a> and Db::set_errcall methods are used to
enhance the mechanism for reporting error messages to the application.
In some cases, when an error occurs, Berkeley DB will call
<b>db_errcall_fcn</b> with additional error information. It is up to
the <b>db_errcall_fcn</b> function to display the error message in an
appropriate manner.</p>
<p>Setting <b>db_errcall_fcn</b> to NULL unconfigures the callback interface.</p>
<p>Alternatively, you can use the <a href="../api_cxx/env_set_error_stream.html">DbEnv::set_error_stream</a> and
<a href="../api_cxx/db_set_error_stream.html">Db::set_error_stream</a> methods to display the additional information via
an output stream, or the <a href="../api_cxx/db_set_errfile.html">Db::set_errfile</a> or
<a href="../api_cxx/env_set_errfile.html">DbEnv::set_errfile</a> methods to display the additional information via a C
library FILE *. You should not mix these approaches.</p>
<p>This error-logging enhancement does not slow performance or significantly
increase application size, and may be run during normal operation as well
as during application debugging.</p>
<p>For <a href="../api_cxx/db_class.html">Db</a> handles opened inside of Berkeley DB environments, calling the
Db::set_errcall method affects the entire environment and is equivalent to calling
the <a href="../api_cxx/env_set_errcall.html">DbEnv::set_errcall</a> method.</p>
<p>The Db::set_errcall method configures operations performed using the specified
<a href="../api_cxx/db_class.html">Db</a> handle, not all operations performed on the underlying
database.</p>
<p>The Db::set_errcall method may be called at any time during the life of the
application.</p>
<b>Parameters</b> <br>
<b>db_errcall_fcn</b><ul compact><li>The <b>db_errcall_fcn</b> parameter is the application-specified error
reporting function. The function takes three parameters:
<br>
<b><b>dbenv</b></b><ul compact><li>The <b>dbenv</b> parameter is the enclosing database environment.</ul>
<b><b>errpfx</b></b><ul compact><li>The <b>errpfx</b> parameter is the prefix string (as previously set by
<a href="../api_cxx/db_set_errpfx.html">Db::set_errpfx</a> or <a href="../api_cxx/env_set_errpfx.html">DbEnv::set_errpfx</a>).</ul>
<b><b>msg</b></b><ul compact><li>The <b>msg</b> parameter is the error message string.</ul>
<br>
<p>Berkeley DB is not re-entrant. Callback functions should not attempt to make
library calls (for example, to release locks or close open handles).
Re-entering Berkeley DB is not guaranteed to work correctly, and the results
are undefined.</p></ul>
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<br><b>Class</b>
<a href="../api_cxx/db_class.html">Db</a>
<br><b>See Also</b>
<a href="../api_cxx/db_list.html">Databases and Related Methods</a>
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