to be returned by the MPI routine that raised the error. If the routine would have returned MPI_ERR_IN_STATUS, it is the error code returned in the status for the request that caused the error handler to be invoked. The remaining arguments are stdargs arguments whose number and meaning is implementation-dependent. An implementation should clearly document these arguments. Addresses are used so that the handler may be written in Fortran.
The MPI-1 Standard states that an implementation may make the output value (errhandler) simply the address of the function. However, the action of MPI_Errhandler_ free makes this impossible, since it is required to set the value of the argument to MPI_ERRHANDLER_NULL. In addition, the actual error handler must remain until all communicators that use it are freed.
Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument. C++ functions do not return errors. If the default error handler is set to MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism will be used to throw an MPI::Exception object.
called. By default, this error handler aborts the MPI job, except for I/O function errors. The error handler may be changed with MPI_Comm_set_errhandler; the predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarantee that an MPI program can continue past an error.