Thanks for the bug report. Does the attached patch to getopt-pfx-core.h fix the
bug for you?
I'll CC: this to bug-gnulib and to Zack Weinberg, who wrote that file. For those
new to this thread, please see <https://bugs.gnu.org/40205>.
diff --git a/lib/getopt-pfx-core.h b/lib/getopt-pfx-core.h
index 31a747d67..a4891bc80 100644
--- a/lib/getopt-pfx-core.h
+++ b/lib/getopt-pfx-core.h
@@ -48,6 +48,14 @@
# define optind __GETOPT_ID (optind)
# define optopt __GETOPT_ID (optopt)
+/* Work around a a problem on macOS, which declares getopt with a
+ trailing __DARWIN_ALIAS(getopt) that would expand to something like
+ __asm("_" "rpl_getopt" "$UNIX2003") were it not for the following
+ hack to suppress the macOS declaration <https://bugs.gnu.org/40205>. */
+# ifdef __APPLE__
+# define _GETOPT
+# endif
+
/* The system's getopt.h may have already included getopt-core.h to
declare the unprefixed identifiers. Undef _GETOPT_CORE_H so that
getopt-core.h declares them with prefixes. */
