#include <db_cxx.h>

void DbEnv::set_errcall(void (*db_errcall_fcn)
    (const Dbenv *dbenv, const char *errpfx, const char *msg));

The DbEnv::set_errcall 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 db_errcall_fcn with additional error information. It is up to the db_errcall_fcn function to display the error message in an appropriate manner.

Setting db_errcall_fcn to NULL unconfigures the callback interface.

Alternatively, you can use the DbEnv::set_error_stream and Db::set_error_stream methods to display the additional information via an output stream, or the Db::set_errfile or DbEnv::set_errfile methods to display the additional information via a C library FILE *. You should not mix these approaches.

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_errcall method configures operations performed using the specified DbEnv handle, not all operations performed on the underlying database environment.

The DbEnv::set_errcall method may be called at any time during the life of the application.

• The db_errcall_fcn parameter is the application-specified error reporting function. The function takes three parameters:
  dbenv
  • The dbenv parameter is the enclosing database environment.
  errpfx
  • The errpfx parameter is the prefix string (as previously set by Db::set_errpfx or DbEnv::set_errpfx).
  msg
  • The msg parameter is the error message string.
  
  

  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.