Merge pull request #13276 from edgargabriel/topic/comm-null-name

comm_get_name: allow MPI_COMM_NULL as argument

Author: edgargabriel

docs/man-openmpi/man3/MPI_Comm_get_name.3.rst

@@ -37,7 +37,8 @@ occurs, :ref:`MPI_Comm_get_name` will return an empty string (all spaces in
 Fortran, "" in C). The three predefined communicators will have
 predefined names associated with them. Thus, the names of
 MPI_COMM_WORLD, MPI_COMM_SELF, and MPI_COMM_PARENT will have the default
-of MPI_COMM_WORLD, MPI_COMM_SELF, and MPI_COMM_PARENT. The fact that the
+of MPI_COMM_WORLD, MPI_COMM_SELF, and MPI_COMM_PARENT (if not MPI_COMM_NULL).
+Passing MPI_COMM_NULL as ``comm`` will return the string MPI_COMM_NULL. The fact that the
 system may have chosen to give a default name to a communicator does not
 prevent the user from setting a name on the same communicator; doing
 this removes the old name and assigns the new one.

ompi/mpi/c/comm_get_name.c.in

@@ -14,6 +14,7 @@
  *                         and Technology (RIST). All rights reserved.
  * Copyright (c) 2024      Triad National Security, LLC. All rights
  *                         reserved.
+ * Copyright (c) 2025      Advanced Micro Devices, Inc. All rights reserverd.
  * $COPYRIGHT$
  *
  * Additional copyrights may follow
@@ -44,7 +45,9 @@ PROTOTYPE ERROR_CLASS comm_get_name(COMM comm, STRING_OUT name, INT_OUT length)
     if ( MPI_PARAM_CHECK ) {
         OMPI_ERR_INIT_FINALIZE(FUNC_NAME);
 
-        if ( ompi_comm_invalid ( comm ) )
+        /* Note that MPI 4.1. explicitely allows to invoke comm_get_name
+           on MPI_COMM_NULL  */
+        if (ompi_comm_invalid(comm) && MPI_COMM_NULL != comm)
             return OMPI_ERRHANDLER_INVOKE ( MPI_COMM_WORLD, MPI_ERR_COMM,
                                             FUNC_NAME);