MPI_ERRHANDLER_CREATE(3)

🎀 NAME 🎀

MPI_Errhandler_create — creates an MPI-style error handler. And okay first things first bestie, this is the Open MPI page for it, and the routine itself is deprecated in favor of MPI_Comm_create_errhandler. Like, it still exists, but she's retired, she's living her soft life now. Use the new one. 💅

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✨ SYNTAX ✨

🌸 C Syntax

#include <mpi.h>

int MPI_Errhandler_create(MPI_Handler_function *function,
     MPI_Errhandler *errhandler)

🦋 Fortran Syntax

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

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

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🍓 INPUT PARAMETER 🍓

• function — user-defined error handling procedure. Yes it's your own little routine, your baby, your creation. 🫶

💜 OUTPUT PARAMETERS 💜

• errhandler — MPI error handler (handle). That's the little ticket you get back. 🎫
• ierror — Fortran only: error status (integer). Fr fr, only the Fortran girlies get this one.

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👑 DESCRIPTION 👑

Okay so note — using this routine is deprecated as of MPI-2, like not even lowkey, it's official. Please use MPI_Comm_create_errhandler instead. Periodt. ✨

So what does it do? It registers your user routine function for use as an MPI error handler. And it returns in errhandler a handle to the registered error handler. Simple. Iconic. ✨

In the C language, the user routine should be a C function of type MPI_Handler_function, which is defined as

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

Now let's break down those args because the way this signature is set up… it's giving very "trust me bro":

• 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. And if the routine would have returned MPI_ERR_IN_STATUS, it's 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.

And why addresses? Because that way the handler may be written in Fortran. 🧚 Cute, right? It's for the cross-language besties.

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💀 NOTE 💀

The MPI 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. So like… it has to be a real handle, bestie. No shortcuts. 🙈

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😭 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. And if there's no communication object associated with the MPI call, then the call is considered attached to MPI_COMM_SELF and will call the associated MPI error handler. Now — 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. And 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. So yeah, something is always catching it. 👑

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

• MPI_ERRORS_ARE_FATAL — causes the program to abort all connected MPI processes. She does not play. 💀
• 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. Very "it depends where you're standing" energy. 🌈
• MPI_ERRORS_RETURN — returns an error code to the application. The chill one. Returns the vibe back to you. 🫶

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. So like… don't assume she'll bounce back. 💅

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.

See also:

• MPI_Comm_create_errhandler
• MPI_Comm_get_errhandler
• MPI_Comm_set_errhandler

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💖 Copyright 💖

2003-2026, The Open MPI Community

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And that's the whole page bestie, slay ✨ — this one's from the Open MPI girlies, dated Sep 10, 2026, and it lives at MPI_ERRHANDLER_CREATE(3). Go forth and handle your errors, you main character. 🎀🦋💜