+\f
+/* Save and restore the instruction and environment pointers,
+ without affecting the signal mask. */
+
+#ifdef HAVE__SETJMP
+typedef jmp_buf sys_jmp_buf;
+# define sys_setjmp(j) _setjmp (j)
+# define sys_longjmp(j, v) _longjmp (j, v)
+#elif defined HAVE_SIGSETJMP
+typedef sigjmp_buf sys_jmp_buf;
+# define sys_setjmp(j) sigsetjmp (j, 0)
+# define sys_longjmp(j, v) siglongjmp (j, v)
+#else
+/* A platform that uses neither _longjmp nor siglongjmp; assume
+ longjmp does not affect the sigmask. */
+typedef jmp_buf sys_jmp_buf;
+# define sys_setjmp(j) setjmp (j)
+# define sys_longjmp(j, v) longjmp (j, v)
+#endif