MPI\_SESSION\_CREATE\_ERRHANDLER(3) Open MPI MPI\_SESSION\_CREATE\_ERRHANDLER(3)

MPI\_Session\_create\_errhandler — Creates an error handler that can be attached to sessions

# [SYNTAX](#SYNTAX)

## [C Syntax](#C_Syntax)

```
#include <mpi.h>
int MPI_Session_create_errhandler(MPI_Session_errhandler_function *function,


    MPI_Errhandler *errhandler)
```

## [Fortran Syntax](#Fortran_Syntax)

```
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_SESSION_CREATE_ERRHANDLER(FUNCTION, ERRHANDLER, IERROR)


    EXTERNAL    FUNCTION


    INTEGER ERRHANDLER, IERROR
```

## [Fortran 2008 Syntax](#Fortran_2008_Syntax)

```
USE mpi_f08
MPI_Session_create_errhandler(session_errhandler_fn, errhandler, ierror)


    PROCEDURE(MPI_Session_errhandler_function) :: session_errhandler_fn


    TYPE(MPI_Errhandler), INTENT(OUT) :: errhandler


    INTEGER, OPTIONAL, INTENT(OUT) :: ierror
```

# [INPUT PARAMETER](#INPUT_PARAMETER)

•

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

# [OUTPUT PARAMETERS](#OUTPUT_PARAMETERS)

- **errhandler** : MPI error handler (handle).
- **ierror** : Fortran only: Error status (integer).

# [DESCRIPTION](#DESCRIPTION)

MPI\_Session\_create\_errhandler creates an error handler that can be attached to sessions. This **function** is identical to MPI\_Errhandler\_create &lt;#mpi-errhandler-create&gt;, the use of which is deprecated. In C, the user routine should be a **function** of type **MPI\_Session\_errhandler\_function**, which is defined as

```
typedef void MPI_Session_errhandler_function(MPI_Session *, int *, ...);
```

The first argument is the session 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 SESSION_ERRHANDLER_FUNCTION(SESSION, ERROR_CODE, ...)


   INTEGER SESSION, ERROR_CODE
```

# [ERRORS](#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 &lt;#mpi-init&gt;/MPI\_Init\_thread &lt;#mpi-init-thread&gt;, after MPI\_Finalize &lt;#mpi-finalize&gt;, 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 &lt;#mpi-comm-set-errhandler&gt; 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 &lt;#mpi-comm-spawn&gt;/MPI\_Comm\_spawn\_multiple &lt;#mpi-comm-spawn-multiple&gt;. 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 &lt;#mpi-abort&gt; was called on that communicator. If called on a window or file, acts as if MPI\_Abort &lt;#mpi-abort&gt; 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 &lt;#mpi-comm-create-errhandler&gt; then MPI\_Comm\_set\_errhandler &lt;#mpi-comm-set-errhandler&gt;
- MPI\_File\_create\_errhandler &lt;#mpi-file-create-errhandler&gt; then MPI\_File\_set\_errhandler &lt;#mpi-file-set-errhandler&gt;
- MPI\_Session\_create\_errhandler then MPI\_Session\_set\_errhandler &lt;#mpi-session-set-errhandler&gt; or at MPI\_Session\_init &lt;#mpi-session-init&gt;
- MPI\_Win\_create\_errhandler &lt;#mpi-win-create-errhandler&gt; then MPI\_Win\_set\_errhandler &lt;#mpi-win-set-errhandler&gt;

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

See the MPI man page &lt;#open-mpi&gt; for a full list of MPI error codes &lt;#open-mpi-errors&gt;.

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

# [Copyright](#Copyright)

2003-2026, The Open MPI Community

September 11, 2026

---

Document: MPI_Session_create_errhandler(3) from openmpi-cuda-13.3 5.0.11-r0 (Chainguard OS)
Source: https://github.com/open-mpi/ompi