--- GCC/gcc/config/rs6000/host-darwin.c	2017-01-09 22:38:14.000000000 +0800
+++ GCC/gcc/config/rs6000/host-darwin.c	2024-09-03 21:29:58.000000000 +0800
@@ -28,20 +28,14 @@
 #include "toplev.h"
 #include "diagnostic.h"
 #include "config/host-darwin.h"
+#include <AvailabilityMacros.h>
 
 static void segv_crash_handler (int);
 static void segv_handler (int, siginfo_t *, void *);
 static void darwin_rs6000_extra_signals (void);
 
-#ifndef HAVE_DECL_SIGALTSTACK
-/* This doesn't have a prototype in signal.h in 10.2.x and earlier,
-   fixed in later releases.  */
-extern int sigaltstack(const struct sigaltstack *, struct sigaltstack *);
-#endif
-
-/* The fields of the mcontext_t type have acquired underscores in later
-   OS versions.  */
-#ifdef HAS_MCONTEXT_T_UNDERSCORES
+/* The fields of the mcontext_t type have acquired underscores in 10.5.  */
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= 1050
 #define MC_FLD(x) __ ## x
 #else
 #define MC_FLD(x) x
