[Mpi-forum] Giving up on C11 _Generic

[HOLMES Daniel]

Hi Jim,

Are we sure the function pointer “worked" in your example? It silently truncated the large value, because the function pointer bypasses the redirection macro.

Cheers,
Dan.
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Dr Daniel Holmes PhD
Architect (HPC Research)
d.holmes at epcc.ed.ac.uk<mailto:d.holmes at epcc.ed.ac.uk>
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On 7 Aug 2019, at 22:00, Jim Dinan via mpi-forum <mpi-forum at lists.mpi-forum.org<mailto:mpi-forum at lists.mpi-forum.org>> wrote:

Even simpler than this, we could just forward all calls to the MPI_Count interface (see below).  The int count argument should type convert to MPI_Count without issue.  Note that it still needs to be a function-like macro so that function pointers work.

Don't give up yet!  :D

 ~Jim.

#include <stdio.h>



typedef int MPI_Datatype;
typedef int MPI_Comm;

int MPI_Send(const void* buf, int count, MPI_Datatype datatype, int dest,
             int tag, MPI_Comm comm)
{
    printf("MPI_Send(count = %d)\n", count);
    return 0;
}

int MPI_Send_x(const void* buf, long long count, MPI_Datatype datatype, int dest,
               int tag, MPI_Comm comm)
{
    printf("MPI_Send_x(count = %lld)\n", count);
    return 0;
}

#define MPI_Send(buf, count, datatype, dest, tag, comm) MPI_Send_x(buf, count, datatype, dest, tag, comm)

int main(int argc, char *argv[]) {
    /* 8589934592LL == 2^33 */
    long long i = 8589934592LL + 11;
    int ret;
    int (*snd_ptr)(const void*, int, MPI_Datatype, int, int, MPI_Comm) = &MPI_Send;
    ret = MPI_Send(NULL, i, 0, 0, 0, 0);
    ret = MPI_Send(NULL, 5, 0, 0, 0, 0);
    ret = (*snd_ptr)(NULL, i, 0, 0, 0, 0);
    ret = (*snd_ptr)(NULL, 5, 0, 0, 0, 0);
    return 0;

}

MPI_Send_x(count = 8589934603)
MPI_Send_x(count = 5)
MPI_Send(count = 11)

MPI_Send(count = 5)
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