MPI_FILE_F2C(3)

💖 MPI_FILE_F2C 💖

okay bestie, so this is the Open MPI page for the whole handle-translation girlie squad ✨ — it's MPI_Comm_f2c, MPI_Comm_c2f, MPI_File_f2c, MPI_File_c2f, MPI_Info_f2c, MPI_Info_c2f, MPI_Message_f2c, MPI_Message_c2f, MPI_Op_f2c, MPI_Op_c2f, MPI_Request_f2c, MPI_Request_c2f, MPI_Type_f2c, MPI_Type_c2f, MPI_Win_f2c, and MPI_Win_c2f — and what they all do is translate a C handle into a Fortran handle, or vice versa. the whole friend group functions as one 🫶

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✨ SYNTAX ✨

🌸 C Syntax 🌸

#include <mpi.h>

MPI_Comm MPI_Comm_f2c(MPI_Fint comm)
MPI_Fint MPI_Comm_c2f(MPI_Comm comm)

MPI_File MPI_File_f2c(MPI_Fint file)
MPI_Fint MPI_File_c2f(MPI_File file)

MPI_Group MPI_Group_f2c(MPI Fint group)
MPI_Fint MPI_Group_c2f(MPI Group group)

MPI_Info MPI_Info_f2c(MPI_Fint info)
MPI_Fint MPI_Info_c2f(MPI_Info info)

MPI_Message MPI_Message_f2c(MPI_Fint message)
MPI_Fint MPI_Message_c2f(MPI_Message message)

MPI_Op MPI_Op_f2c(MPI_Fint op)
MPI_Fint MPI_Op_c2f(MPI_Op op)

MPI_Request MPI_Request_f2c(MPI_Fint request)
MPI_Fint MPI_Request_c2f(MPI_Request request)

MPI_Datatype MPI_Type_f2c(MPI_Fint datatype)
MPI_Fint MPI_Type_c2f(MPI_Datatype datatype)

MPI_Win MPI_Win_f2c(MPI_Fint win)
MPI_Fint MPI_Win_c2f(MPI_Win win)

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💅 DESCRIPTION 💅

okay so here's the tea 🍓: handles get passed between Fortran and C by using an explicit C wrapper to convert Fortran handles into C handles. that's it, that's the girlie. there is no direct access to C handles in Fortran — like, none, don't even try, it's giving boundary. 🙈

the type definition MPI_Fint is provided in C for an integer of the size that matches a Fortran INTEGER; usually, MPI_Fint will be equivalent to int. (imagine matching sizes with your bestie, iconic 💞)

and then the handle translation functions are provided in C to convert from a Fortran handle (which, yes, is just an integer 💀) to a C handle, and vice versa. both directions, no cap.

for example, if comm is a valid Fortran handle to a communicator, then MPI_Comm_f2c returns a valid C handle to that same communicator; if comm = MPI_COMM_NULL (Fortran value), then MPI_Comm_f2c returns a null C handle; if comm is an invalid Fortran handle, then MPI_Comm_f2c returns an invalid C handle. garbage in, garbage out, she said it herself 💀

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📌 NOTE 📌

bestie, listen — this function does not return an error value. consequently, the result of calling it before MPI_Init or after MPI_Finalize is undefined. not "undefined-ish", not "probably fine" — genuinely undefined, so don't be the main character who does this. 😭

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🎀 Copyright 🎀

2003-2026, The Open MPI Community

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and that's the whole page, bestie 🦋 slay. this was the Open MPI rendition, dated Sep 10, 2026, and yes she ate 💅✨