MPI\_GROUP\_F2C(3) Open MPI MPI\_GROUP\_F2C(3)

MPI\_Comm\_f2c <#mpi-comm-f2c>, MPI\_Comm\_c2f <#mpi-comm-c2f>, MPI\_File\_f2c <#mpi-file-f2c>, MPI\_File\_c2f <#mpi-file-c2f>, MPI\_Info\_f2c <#mpi-info-f2c>, MPI\_Info\_c2f <#mpi-info-c2f>, MPI\_Message\_f2c <#mpi-message-f2c>, MPI\_Message\_c2f <#mpi-message-c2f>, MPI\_Op\_f2c <#mpi-op-f2c>, MPI\_Op\_c2f <#mpi-op-c2f>, MPI\_Request\_f2c <#mpi-request-f2c>, MPI\_Request\_c2f <#mpi-request-c2f>, MPI\_Type\_f2c <#mpi-type-f2c>, MPI\_Type\_c2f <#mpi-type-c2f>, MPI\_Win\_f2c <#mpi-win-f2c>, MPI\_Win\_c2f <#mpi-win-c2f> - Translates a C handle into a Fortran handle, or vice versa.

# [SYNTAX](#SYNTAX)

## [C 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)
```

# [DESCRIPTION](#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 &lt;#mpi-comm-f2c&gt; returns a valid C handle to that same communicator; if *comm* = MPI\_COMM\_NULL (Fortran value), then MPI\_Comm\_f2c &lt;#mpi-comm-f2c&gt; returns a null C handle; if *comm* is an invalid Fortran handle, then MPI\_Comm\_f2c &lt;#mpi-comm-f2c&gt; returns an invalid C handle.

# [NOTE](#NOTE)

This function does not return an error value. Consequently, the result of calling it before MPI\_Init &lt;#mpi-init&gt; or after MPI\_Finalize &lt;#mpi-finalize&gt; is undefined.

# [Copyright](#Copyright)

2003-2026, The Open MPI Community

July 6, 2026

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Document: MPI_Group_f2c(3) from openmpi-cuda-12.4 5.0.10-r2 (Chainguard OS)
Source: https://github.com/open-mpi/ompi