When an error occurs in the Berkeley DB library, an exception is thrown or an
error return value is returned by the method. In some cases,
however, the errno value may be insufficient to completely
describe the cause of the error, especially during initial application
debugging.
The DbEnv::set_errfile method is used to enhance the mechanism for reporting error
messages to the application by setting a C library FILE * to be used for
displaying additional Berkeley DB error messages. In some cases, when an error
occurs, Berkeley DB will output an additional error message to the specified
file reference.
Alternatively, you can use the DbEnv::set_error_stream method to display
the additional information via an output stream, or the
DbEnv::set_errcall method to capture the additional error information in
a way that does not use either output streams or C library FILE *'s. You
should not mix these approaches.
The error message will consist of the prefix string and a colon
(":") (if a prefix string was previously specified using
Db::set_errpfx or DbEnv::set_errpfx), an error string, and
a trailing <newline> character.
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.
The DbEnv::set_errfile interface may be used to configure Berkeley DB at any time
during the life of the application.