[src/trunk]: src/lib/libc/gen Clarify what happens when you longjmp(..., 0).

[riastradh <riastradh%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/bca08b0e2a6c
branches:  trunk
changeset: 1021302:bca08b0e2a6c
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Mon May 24 23:59:59 2021 +0000

description:
Clarify what happens when you longjmp(..., 0).

Derived from C99 7.13.2.1 `The longjmp function'.

diffstat:

 lib/libc/gen/setjmp.3 |  11 ++++++++++-
 1 files changed, 10 insertions(+), 1 deletions(-)

diffs (25 lines):

diff -r ab66d4285b05 -r bca08b0e2a6c lib/libc/gen/setjmp.3
--- a/lib/libc/gen/setjmp.3     Mon May 24 23:07:40 2021 +0000
+++ b/lib/libc/gen/setjmp.3     Mon May 24 23:59:59 2021 +0000
@@ -1,4 +1,4 @@
-.\"    $NetBSD: setjmp.3,v 1.17 2008/05/31 16:15:07 enami Exp $
+.\"    $NetBSD: setjmp.3,v 1.18 2021/05/24 23:59:59 riastradh Exp $
 .\"
 .\" Copyright (c) 1990, 1991, 1993
 .\"    The Regents of the University of California.  All rights reserved.
@@ -85,6 +85,15 @@
 call had just returned the value specified by
 .Fa val ,
 instead of 0.
+The
+.Fn longjmp
+functions cannot cause
+.Fn setjmp
+to return 0; if
+.Fa val
+is 0,
+.Fn setjmp
+returns 1 instead.
 .Pp
 Pairs of calls may be intermixed, i.e., both
 .Fn sigsetjmp