Correctly set the app cmd and argv0 fields

Ensure that the cmd field always gets set, or return
an error if it wasn't provided and neither was argv.
If cmd is not set, then take it from argv0.

Ensure that argv0 is always the basename of cmd so
that the spawned app sees the expected name in
that location.

Fix a bug in the transferrence of the app's argv
to the internal structure.

Signed-off-by: Ralph Castain <rhc@pmix.org>

src/client/pmix_client_spawn.c

@@ -8,7 +8,7 @@
  * Copyright (c) 2016      Mellanox Technologies, Inc.
  *                         All rights reserved.
  * Copyright (c) 2016      IBM Corporation.  All rights reserved.
- * Copyright (c) 2021-2023 Nanook Consulting.  All rights reserved.
+ * Copyright (c) 2021-2024 Nanook Consulting  All rights reserved.
  * $COPYRIGHT$
  *
  * Additional copyrights may follow
@@ -195,7 +195,7 @@ PMIX_EXPORT pmix_status_t PMIx_Spawn_nb(const pmix_info_t job_info[], size_t nin
     PMIX_APP_CREATE(appsptr, napps);
     for (n = 0; n < napps; n++) {
         aptr = (pmix_app_t *) &apps[n];
-        /* protect against idiot case (yes, they exist) */
+        /* protect against bozo case */
         if (NULL == aptr->cmd && NULL == aptr->argv) {
             /* they gave us nothing to spawn! */
             PMIX_APP_FREE(appsptr, napps);
@@ -204,7 +204,13 @@ PMIX_EXPORT pmix_status_t PMIx_Spawn_nb(const pmix_info_t job_info[], size_t nin
             }
             return PMIX_ERR_BAD_PARAM;
         }
-        appsptr[n].cmd = strdup(aptr->cmd);
+        if (NULL == aptr->cmd) {
+            // aptr->argv cannot be NULL as well or we
+            // would have caught it above
+            appsptr[n].cmd = strdup(aptr->argv[0]);
+        } else {
+            appsptr[n].cmd = strdup(aptr->cmd);
+        }
 
         /* if they didn't give us a desired working directory, then
          * take the one we are in */
@@ -233,7 +239,8 @@ PMIX_EXPORT pmix_status_t PMIx_Spawn_nb(const pmix_info_t job_info[], size_t nin
             tmp = pmix_basename(aptr->cmd);
             t2 = pmix_basename(aptr->argv[0]);
             if (0 != strcmp(tmp, t2)) {
-                PMIx_Argv_prepend_nosize(&appsptr[n].argv, tmp);
+                free(appsptr[n].argv[0]);
+                appsptr[n].argv[0] = strdup(tmp);
             }
             free(tmp);
             free(t2);