Clarify sigsetjmp vs. setjmp vs. _setjmp.

1 files changed, 35 insertions, 1 deletions

diff --git a/lib/libc/gen/setjmp.3 b/lib/libc/gen/setjmp.3
index 33ceb09bcaf..bf27c5ff991 100644
--- a/lib/libc/gen/setjmp.3
+++ b/lib/libc/gen/setjmp.3
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: setjmp.3,v 1.11 2000/12/24 00:30:51 aaron Exp $
+.\"	$OpenBSD: setjmp.3,v 1.12 2001/01/12 21:28:19 millert Exp $
 .\"
 .\" Copyright (c) 1990, 1991, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -132,6 +132,28 @@ function pairs save and restore the signal mask if the argument
 .Fa savemask
 is non-zero.
 Otherwise, only the register set and the stack are saved.
+.Pp
+In other words,
+.Fn setjmp Ns / Ns Fn longjmp
+are functionally equivalent to
+.Fn sigsetjmp Ns / Ns Fn siglongjmp
+when
+.Fn sigsetjmp
+is called with a non-zero
+.Fa savemask
+argument.
+Conversely,
+.Fn _setjmp Ns / Ns Fn _longjmp
+are functionally equivalent to
+.Fn sigsetjmp Ns / Ns Fn siglongjmp
+when 
+.Fn sigsetjmp
+is called with a zero-value
+.Fa savemask .
+.Pp
+The
+.Fn sigsetjmp Ns / Ns Fn siglongjmp
+interfaces are preferred for maximum portability.
 .Sh ERRORS
 If the contents of the
 .Fa env
@@ -169,3 +191,15 @@ and
 .Fn siglongjmp
 functions conform to
 .St -p1003.1-90 .
+.Sh CAVEATS
+Historically, on
+.At V ,
+the
+.Fn setjmp Ns / Ns Fn longjmp
+functions have been equivalent to the
+.Bx
+.Fn _setjmp Ns / Ns Fn _longjmp
+functions and do not restore the signal mask.
+Because of this discrepancy, the
+.Fn sigsetjmp Ns / Ns Fn siglongjmp
+interfaces should be used if portability is desired.