Make sure we do the right thing with refcounts on errhandler

This commit was SVN r989.

src/mpi/c/comm_create_errhandler.c

@@ -29,13 +29,14 @@ int MPI_Comm_create_errhandler(MPI_Comm_errhandler_fn *function,
     }
   }
 
-  /* Create and cache the errhandler */
+  /* Create and cache the errhandler.  Sets a refcount of 1. */
 
   *errhandler = 
     lam_errhandler_create(LAM_ERRHANDLER_TYPE_COMM,
                           (lam_errhandler_fortran_handler_fn_t*) function);
-  if (NULL == *errhandler)
+  if (NULL == *errhandler) {
     err = MPI_ERR_INTERN;
+  }
 
   LAM_ERRHANDLER_RETURN(err, MPI_COMM_WORLD, MPI_ERR_INTERN,
                         "MPI_Comm_create_errhandler");

src/mpi/c/comm_get_errhandler.c

@@ -29,7 +29,8 @@ int MPI_Comm_get_errhandler(MPI_Comm comm, MPI_Errhandler *errhandler)
     }
   }
 
-  /* Return the errhandler */
+  /* Return the errhandler.  Do not increase the refcount here; we
+     only refcount on communicators */
 
   *errhandler = comm->error_handler;
 

src/mpi/c/comm_set_errhandler.c

@@ -31,11 +31,11 @@ int MPI_Comm_set_errhandler(MPI_Comm comm, MPI_Errhandler errhandler)
     }
   }
 
-  /* Ditch the old errhandler */
+  /* Ditch the old errhandler, and decrement its refcount */
 
   OBJ_RELEASE(comm->error_handler);
 
-  /* We have a valid comm and errhandler */
+  /* We have a valid comm and errhandler, so increment its refcount */
 
   comm->error_handler = errhandler;
   OBJ_RETAIN(comm->error_handler);