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

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

diff --git a/cmd/tools/gc.c b/cmd/tools/gc.c
index cafe39d3f52db14abef3c0bc394e097f734aefad..70e2bd78ac9e798e6e03fefee0ca5892ba56166c 100644 (file)
--- a/cmd/tools/gc.c
+++ b/cmd/tools/gc.c
@@ -123,7 +123,7 @@ static void init(int argc, char *argv[])
            gtype = UNDIRECTED;
            break;
        case '?':
-           if (optopt == '\0')
+           if (optopt == '\0' || optopt == '?')
                usage(0);
            else {
                fprintf(stderr, "gc: option -%c unrecognized\n",