+#define SIG_MEMORY_FAULT SIGSEGV
+
+#elif defined __NetBSD__
+
+#include <ucontext.h>
+typedef ucontext_t os_context_t;
+#define SIG_MEMORY_FAULT SIGSEGV
+
+#elif defined LISP_FEATURE_DARWIN
+ /* man pages claim that the third argument is a sigcontext struct,
+ but ucontext_t is defined, matches sigcontext where sensible,
+ offers better access to mcontext, and is of course the SUSv2-
+ mandated type of the third argument, so we use that instead.
+ If Apple is going to break ucontext_t out of spite, I'm going
+ to be cross with them ;) -- PRM */
+
+#include <ucontext.h>
+typedef ucontext_t os_context_t;
+#define SIG_MEMORY_FAULT SIGBUS
+