Fix gvmap -? to actually print usage instead of error on macOS

Towards https://gitlab.com/graphviz/graphviz/-/issues/1852.

diff --git a/cmd/gvmap/gvmap.c b/cmd/gvmap/gvmap.c
index 5fa4c934e3e6b3f5f19243ea8af998a01db2d167..8de13a610fbeae9461b04602adbfc375332512f3 100644 (file)
--- a/cmd/gvmap/gvmap.c
+++ b/cmd/gvmap/gvmap.c
@@ -389,7 +389,7 @@ init(int argc, char **argv, params_t* pm)
       fprintf(stderr, "gvpack: option -%c missing argument - ignored\n", optopt);
       break;
     case '?':
-      if (optopt == '\0')
+      if (optopt == '\0' || optopt == '?')
         usage(cmd, 0);
       else {
         fprintf(stderr, " option -%c unrecognized\n", optopt);