Merge pull request #7323 from bosilca/fix/7320

Trap wrong parameters to MPI_Init_thread.

ompi/errhandler/errhandler_predefined.c

@@ -61,7 +61,7 @@ void ompi_mpi_errors_are_fatal_comm_handler(struct ompi_communicator_t **comm,
 
   va_start(arglist, error_code);
 
-  if (NULL != comm) {
+  if ( (NULL != comm) && (NULL != *comm) ) {
       name = (*comm)->c_name;
       abort_comm = *comm;
   } else {

ompi/mpi/c/init_thread.c

@@ -47,26 +47,36 @@ static const char FUNC_NAME[] = "MPI_Init_thread";
 int MPI_Init_thread(int *argc, char ***argv, int required,
                     int *provided)
 {
-    int err;
+    int err, safe_required = MPI_THREAD_SERIALIZED;
 
     ompi_hook_base_mpi_init_thread_top(argc, argv, required, provided);
 
-    if ( MPI_PARAM_CHECK ) {
-        if (required < MPI_THREAD_SINGLE || required > MPI_THREAD_MULTIPLE) {
-            ompi_mpi_errors_are_fatal_comm_handler(NULL, NULL, FUNC_NAME);
-        }
+    /* Detect an incorrect thread support level, but dont report until we have the minimum
+     * infrastructure setup.
+     */
+    if( (MPI_THREAD_SINGLE == required) || (MPI_THREAD_SERIALIZED == required) ||
+        (MPI_THREAD_FUNNELED == required) || (MPI_THREAD_MULTIPLE == required) ) {
+        safe_required = required;
     }
 
-    *provided = required;
+    *provided = safe_required;
 
     /* Call the back-end initialization function (we need to put as
        little in this function as possible so that if it's profiled, we
        don't lose anything) */
 
     if (NULL != argc && NULL != argv) {
-        err = ompi_mpi_init(*argc, *argv, required, provided, false);
+        err = ompi_mpi_init(*argc, *argv, safe_required, provided, false);
     } else {
-        err = ompi_mpi_init(0, NULL, required, provided, false);
+        err = ompi_mpi_init(0, NULL, safe_required, provided, false);
+    }
+
+    if( safe_required != required ) {
+        /* Trigger the error handler for the incorrect argument. Keep it separate from the
+         * check on the ompi_mpi_init return and report a nice, meaningful error message to
+         * the user. */
+        return ompi_errhandler_invoke((ompi_errhandler_t*)&ompi_mpi_errors_are_fatal, NULL, OMPI_ERRHANDLER_TYPE_COMM,
+                                      MPI_ERR_ARG, FUNC_NAME);
     }
 
     /* Since we don't have a communicator to invoke an errorhandler on