# 17.2.49. MPI_Comm_create_errhandler

MPI_Comm_create_errhandler — Creates an error handler that can be attached to communicators.

## 17.2.49.1. SYNTAX

### 17.2.49.1.1. C Syntax

    #include <mpi.h>

    int MPI_Comm_create_errhandler(MPI_Comm_errhandler_function *function,
        MPI_Errhandler *errhandler)

### 17.2.49.1.2. Fortran Syntax

    USE MPI
    ! or the older form: INCLUDE 'mpif.h'

    MPI_COMM_CREATE_ERRHANDLER(FUNCTION, ERRHANDLER, IERROR)
        EXTERNAL    FUNCTION
        INTEGER ERRHANDLER, IERROR

### 17.2.49.1.3. Fortran 2008 Syntax

    USE mpi_f08

    MPI_Comm_create_errhandler(comm_errhandler_fn, errhandler, ierror)
        PROCEDURE(MPI_Comm_errhandler_function) :: comm_errhandler_fn
        TYPE(MPI_Errhandler), INTENT(OUT) :: errhandler
        INTEGER, OPTIONAL, INTENT(OUT) :: ierror

## 17.2.49.2. Deprecated Type Name Note

MPI-2.2 deprecated the `MPI_Comm_errhandler_fn` type in favor of `MPI_Comm_errhandler_function`. Open MPI supports both names (indeed, the `_fn` names are typedefs to the `_function` names).

## 17.2.49.3. INPUT PARAMETER

- `function` : User-defined error handling procedure (function).

## 17.2.49.4. OUTPUT PARAMETERS

- `errhandler` : MPI error handler (handle).

- `ierror` : Fortran only: Error status (integer).

## 17.2.49.5. DESCRIPTION

MPI_Comm_create_errhandler creates an error handler that can be attached to communicators. This `function` is identical to MPI_Errhandler_create, the use of which is deprecated. In C, the user routine should be a `function` of type `MPI_Comm_errhandler_function`, which is defined as

    typedef void MPI_Comm_errhandler_function(MPI_Comm *, int *, ...);

The first argument is the communicator in use. The second is the error code to be returned by the MPI routine that raised the error. This typedef replaces `MPI_Handler_function`, the use of which is deprecated. In Fortran, the user routine should be of this form:

    SUBROUTINE COMM_ERRHANDLER_FUNCTION(COMM, ERROR_CODE, ...)
       INTEGER COMM, ERROR_CODE

## 17.2.49.6. ERRORS

Almost all MPI routines return an error value; C routines as the return result of the function and Fortran routines in the last argument.

Before the error value is returned, the current MPI error handler associated with the communication object (e.g., communicator, window, file) is called. If no communication object is associated with the MPI call, then the call is considered attached to MPI_COMM_SELF and will call the associated MPI error handler. When MPI_COMM_SELF is not initialized (i.e., before MPI_Init/MPI_Init_thread, after MPI_Finalize, or when using the Sessions Model exclusively) the error raises the initial error handler. The initial error handler can be changed by calling MPI_Comm_set_errhandler on MPI_COMM_SELF when using the World model, or the mpi_initial_errhandler CLI argument to mpiexec or info key to MPI_Comm_spawn/MPI_Comm_spawn_multiple. If no other appropriate error handler has been set, then the MPI_ERRORS_RETURN error handler is called for MPI I/O functions and the MPI_ERRORS_ABORT error handler is called for all other MPI functions.

Open MPI includes three predefined error handlers that can be used:

- `MPI_ERRORS_ARE_FATAL` Causes the program to abort all connected MPI processes.

- `MPI_ERRORS_ABORT` An error handler that can be invoked on a communicator, window, file, or session. When called on a communicator, it acts as if MPI_Abort was called on that communicator. If called on a window or file, acts as if MPI_Abort was called on a communicator containing the group of processes in the corresponding window or file. If called on a session, aborts only the local process.

- `MPI_ERRORS_RETURN` Returns an error code to the application.

MPI applications can also implement their own error handlers by calling:

- MPI_Comm_create_errhandler then MPI_Comm_set_errhandler

- MPI_File_create_errhandler then MPI_File_set_errhandler

- MPI_Session_create_errhandler then MPI_Session_set_errhandler or at MPI_Session_init

- MPI_Win_create_errhandler then MPI_Win_set_errhandler

Note that MPI does not guarantee that an MPI program can continue past an error.

See the MPI man page for a full list of MPI error codes.

See the Error Handling section of the MPI-3.1 standard for more information.