Index: /trunk/ccl/lisp-kernel/x86-exceptions.h
===================================================================
--- /trunk/ccl/lisp-kernel/x86-exceptions.h	(revision 6218)
+++ /trunk/ccl/lisp-kernel/x86-exceptions.h	(revision 6219)
@@ -83,8 +83,6 @@
 #endif
 
-#ifdef USE_SIGALTSTACK
-void setup_sigaltstack(area *);
+
 void switch_to_foreign_stack(void*, ...);
-#endif
 
 #define INTN_OPCODE 0xcd
@@ -141,2 +139,14 @@
 extern void set_gs_address(void *);
 #endif
+
+
+/* sigaltstack isn't thread-specific on The World's Most Advanced OS */
+#ifdef DARWIN
+#undef USE_SIGALTSTACK
+#else
+#define USE_SIGALTSTACK 1
+#endif
+
+#ifdef USE_SIGALTSTACK
+void setup_sigaltstack(area *);
+#endif