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

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

diff --git a/cmd/tools/gvcolor.c b/cmd/tools/gvcolor.c
index e73bf9cad66a4feebbd39c5babd7cdb2704ded5c..62c55507eaa6b70dc4902f55f3abf50e0f204109 100644 (file)
--- a/cmd/tools/gvcolor.c
+++ b/cmd/tools/gvcolor.c
@@ -91,7 +91,7 @@ static void init(int argc, char *argv[])
     while ((c = getopt(argc, argv, ":?")) != -1) {
        switch (c) {
        case '?':
-           if (optopt == '\0')
+           if (optopt == '\0' || optopt == '?')
                usage(0);
            else {
                fprintf(stderr, "gvcolor: option -%c unrecognized\n",