[OMPI users] openmpi MPI_Init doesn't work after fork under gdb

[Geoffrey Irving]

The attached program illustrates the problem.  It forks, and the child
calls MPI_Init.  This works fine unless I'm inside gdb.  Inside gdb,
MPI_Init silently crashes.

I'm using OpenMPI 1.6.0 on Mac 10.8.2.  I'm running the program
directly, not through mpirun.

Any ideas what might be wrong?

Thanks,
Geoffrey

cone:scratch% /usr/local/bin/mpicc -o fork-bug fork-bug.c
cone:scratch% ./fork-bug
We're an MPI program!
child status = 0
cone:scratch% gdb ./fork-bug
gdb ./fork-bug
GNU gdb 6.3.50-20050815 (Apple version gdb-1824) (Thu Nov 15 10:42:43 UTC 2012)
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "x86_64-apple-darwin"...Reading symbols for
shared libraries ... done

(gdb) run
Reading symbols for shared libraries ++............................. done
child status = 5

Program exited normally.
(gdb) cone:scratch%

#include <mpi.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/wait.h>
#include <string.h>
#include <errno.h>

#define CAREFUL 0

#if CAREFUL

int main(int argc, char** argv) {
  int pid = fork();
  if (pid < 0) {
    printf("fork failed: %s\n",strerror(errno));
    return 1;
  }
  if (pid) { // Parent
    int status;
    pid = wait(&status);
    if (pid < 0) {
      printf("wait failed: %s\n",strerror(errno));
      return 1;
    }
    printf("child status = %d\n",status);
  } else { // Child
    int r = MPI_Init(&argc,&argv);
    if (r != MPI_SUCCESS) {
      printf("MPI_Init failed: r = %d\n",r);
      return 1;
    }
    printf("We're an MPI program!\n");
    r = MPI_Finalize();
    if (r != MPI_SUCCESS) {
      printf("MPI_Finalized failed: r = %d\n",r);
      return 1;
    }
  }
  // Everything worked
  return 0;
}

#else

int main(int argc, char** argv) {
  int pid = fork();
  if (pid) { // Parent
    int status;
    wait(&status);
    printf("child status = %d\n",status);
  } else { // Child
    MPI_Init(&argc,&argv);
    printf("We're an MPI program!\n");
    MPI_Finalize();
  }
  return 0;
}

#endif