MPIX_Win_create_errhandler_x(3)

💖 MPIX_Win_create_errhandler_x — from the MPI manual, bestie 💖

okay so. real talk. this one is a cute little MPIX function that creates an MPI-style window errorhandler... but with a lil twist: it takes an extra_state. yes queen, extra. state. slay. ✨

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✨ NAME ✨

MPIX_Win_create_errhandler_x — makes an MPI-style window errorhandler that also carries an extra_state 🎀

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🦋 SYNOPSIS 🦋

int MPIX_Win_create_errhandler_x(MPIX_Win_errhandler_function_x *comm_errhandler_fn_x,
MPIX_Destructor_function *destructor_fn,
void *extra_state, MPI_Errhandler *errhandler)

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🌸 INPUT PARAMETERS 🌸

• comm_errhandler_fn_x — the user-defined error handling procedure, but make it the extra_state-having kind. it's a function. no cap. 💅
• destructor_fn — the callback that fires when the op gets freed. also a function. 🧚
• extra_state — extra state. value is None. that's it, that's the whole vibe. 💜

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👑 OUTPUT PARAMETERS 👑

• errhandler — the MPI error handler. it's a handle. 🫶

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🔥 THREAD AND INTERRUPT SAFETY 🔥

okay so this routine is thread-safe. meaning what exactly? meaning you can hit it from multiple threads at the same time and you do not need to bring your own thread locks. no user-provided lock era. we love that for us. 😌

BUT. and this is the crucial BUT — it is not interrupt safe. not even a little. why? typically because of memory allocation routines like malloc, or other non-MPICH runtime routines, that are themselves not interrupt-safe. so like... it's giving "safe from threads, not safe from interrupts." know the difference bestie, it matters. 💀

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🎀 NOTES FOR FORTRAN 🎀

every single MPI routine in Fortran (except for MPI_WTIME and MPI_WTICK, those two are the exception girlies) has an extra argument called ierr tacked on at the very end of the argument list.

ierr is an integer, and it means exactly the same thing as the return value of the routine in C. same energy, different syntax.

also: in Fortran, MPI routines are subroutines, and you invoke them with the call statement. that's just how it is.

and one more for the road: all MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGER in Fortran. every single one. periodt. 💖

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🌈 ERRORS 🌈

okay so every MPI routine (except MPI_Wtime and MPI_Wtick, the eternal exceptions) returns an error value. in C it's the value of the function, in Fortran it's in that last argument. before the value comes back to you, the current MPI error handler gets called. and by default? that error handler aborts the MPI job. yes, the whole thing. dramatic but true. 😭

you can swap the error handler out with:

• MPI_Comm_set_errhandler — for communicators
• MPI_File_set_errhandler — for files
• MPI_Win_set_errhandler — for RMA windows

the MPI-1 routine MPI_Errhandler_set also exists and may be used, but its use is deprecated — so like, don't, bestie. 🙈

the predefined error handler MPI_ERRORS_RETURN may be used to make error values get returned instead.

⚠️ heads up: MPI does not guarantee that an MPI program can continue past an error. however, MPI implementations will attempt to continue whenever possible. so it's giving "we'll try," not "we promise." 💫

the actual error codes:

• MPI_SUCCESS — no error; the MPI routine completed successfully. we ate. 👑
• MPI_ERR_ARG — invalid argument. some argument is invalid and it's not identified by a specific error class (e.g., MPI_ERR_RANK). she's unidentified and thriving. 💅
• MPI_ERR_OTHER — other error; use MPI_Error_string to get more information about this error code. mystery flavor. 🍓

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and that's the whole page, bestie. MPIX_Win_create_errhandler_x — she creates an MPI-style window errorhandler, she brings her own extra_state, she's thread-safe but not interrupt-safe, and she lives in the MPI manual. 💖

this page is dated 4/10/2026 and it's MPIX_Win_create_errhandler_x(3) — go forth and create those errorhandlers, you absolute icon. 🎀✨🦋