while (cmdline[++src]
                                        && isspace(cmdline[src]))
                                ; /* skip */
-                       if (count >= size) {
-                               size += 16;
-                               *argv = xrealloc(*argv, sizeof(char *) * size);
-                       }
+                       ALLOC_GROW(*argv, count+1, size);
                        (*argv)[count++] = cmdline + dst;
                } else if (!quoted && (c == '\'' || c == '"')) {
                        quoted = c;
                return error("unclosed quote");
        }
 
+       ALLOC_GROW(*argv, count+1, size);
+       (*argv)[count] = NULL;
+
        return count;
 }