1 files changed, 24 insertions, 2 deletions
diff --git a/jbwrap.h b/jbwrap.h
index 4074a32..e8a0790 100644
--- a/jbwrap.h
+++ b/jbwrap.h
@@ -1,9 +1,31 @@
 #include <setjmp.h>
 
-/* certain braindamaged environments don't define jmp_buf as an array, so... */
+/* If we have POSIX sigjmp_buf and friends, use them.  If we don't, just
+use a jmp_buf.  This probably fails on a traditional SysV machine, where
+jmp_bufs don't preserve signal masks.  I'm not worrying about this till
+someone reports it as a bug :-). */
+
+#if HAVE_SIGSETJMP
+#else
+#define sigjmp_buf jmp_buf
+#define sigsetjmp(x,y) setjmp(x)
+#define siglongjmp longjmp
+#endif /* HAVE_SIGSETJMP */
+
+
+/* Certain braindamaged environments don't define jmp_buf as an array,
+so wrap it in a structure.  Potentially, we could use configure to do
+this only where it needs to be done, but the effort is probably not
+worth it. */
 
 struct Jbwrap {
 	sigjmp_buf j;
 };
 
-extern Jbwrap slowbuf; /* for getting out of interrupts while performing slow i/o on BSD */
+
+/* The slowbuf jump buffer is used to prevent "slow" system calls being
+restarted on systems like BSD where they are restarted after a signal. */
+
+#if HAVE_RESTARTABLE_SYSCALLS
+extern Jbwrap slowbuf;
+#endif