# 18.2.301. MPI_Request_f2c

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, MPI_Win_c2f - Translates a C handle into a Fortran handle, or vice versa.

## 18.2.301.1. SYNTAX

### 18.2.301.1.1. 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)

## 18.2.301.2. DESCRIPTION

Handles are passed between Fortran and C by using an explicit C wrapper to convert Fortran handles to C handles. There is no direct access to C handles in Fortran. 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. The handle translation functions are provided in C to convert from a Fortran handle (which is an integer) to a C handle, and vice versa.

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.

## 18.2.301.3. NOTE

This function does not return an error value. Consequently, the result of calling it before MPI_Init or after MPI_Finalize is undefined.