[src/trunk]: src/sys/sys Try to appease KUBSan in sys/sys/wait.h in W_EXITCODE()

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

details:   https://anonhg.NetBSD.org/src/rev/b0b08a7a5278
branches:  trunk
changeset: 833622:b0b08a7a5278
user:      kamil <kamil%NetBSD.org@localhost>
date:      Tue Jul 03 22:38:33 2018 +0000

description:
Try to appease KUBSan in sys/sys/wait.h in W_EXITCODE()

Cast return value that is stored as int to unsigned int in order to
appease the << 8 operation. In case of a ret=-1, this cast is papering
things over or replacing UB with an implementation specific behavior.

There is a reverse operation with the same papering things over:
WEXITSTATUS(x)  ((int)(((unsigned int)_W_INT(x)) >> 8) & 0xff)

No functional change intended.

Detected with Kernel Undefined Behavior Sanitizer.

Reported by <Harry Pantazis>

diffstat:

 sys/sys/wait.h |  4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diffs (18 lines):

diff -r 843ef8c10209 -r b0b08a7a5278 sys/sys/wait.h
--- a/sys/sys/wait.h    Tue Jul 03 21:12:10 2018 +0000
+++ b/sys/sys/wait.h    Tue Jul 03 22:38:33 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: wait.h,v 1.35 2016/11/10 18:35:17 christos Exp $       */
+/*     $NetBSD: wait.h,v 1.36 2018/07/03 22:38:33 kamil Exp $  */
 
 /*
  * Copyright (c) 1982, 1986, 1989, 1993, 1994
@@ -69,7 +69,7 @@
 #define        WCOREFLAG       0200
 #define WCOREDUMP(x)   (_W_INT(x) & WCOREFLAG)
 
-#define        W_EXITCODE(ret, sig)    ((ret) << 8 | (sig))
+#define        W_EXITCODE(ret, sig)    ((unsigned int)(ret) << 8 | (sig))
 #define        W_STOPCODE(sig)         ((sig) << 8 | _WSTOPPED)
 #define        W_CONTCODE()            (_WCONTINUED)
 #endif