[src/trunk]: src/sys/sys Avoid undefined behaviour in shifts in endian decodi...

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

details:   https://anonhg.NetBSD.org/src/rev/b9047465ecf4
branches:  trunk
changeset: 327843:b9047465ecf4
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Tue Mar 18 14:28:37 2014 +0000

description:
Avoid undefined behaviour in shifts in endian decoding routines.

If int is 32-bit and p is a uint8_t *, then p[0] is promoted to int
and p[0] << 24 can shift a one into the sign bit of an int, which is
nasal demon territory.

diffstat:

 sys/sys/endian.h |  10 +++++-----
 1 files changed, 5 insertions(+), 5 deletions(-)

diffs (45 lines):

diff -r b123d0bcea83 -r b9047465ecf4 sys/sys/endian.h
--- a/sys/sys/endian.h  Tue Mar 18 13:10:27 2014 +0000
+++ b/sys/sys/endian.h  Tue Mar 18 14:28:37 2014 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: endian.h,v 1.28 2009/08/08 21:23:15 christos Exp $     */
+/*     $NetBSD: endian.h,v 1.29 2014/03/18 14:28:37 riastradh Exp $    */
 
 /*
  * Copyright (c) 1987, 1991, 1993
@@ -250,7 +250,7 @@
 {
        const uint8_t *p = __CAST(const uint8_t *, buf);
 
-       return __CAST(uint16_t, ((p[0] << 8) | p[1]));
+       return ((__CAST(uint16_t, p[0]) << 8) | p[1]);
 }
 
 static __inline uint16_t __unused
@@ -258,7 +258,7 @@
 {
        const uint8_t *p = __CAST(const uint8_t *, buf);
 
-       return __CAST(uint16_t, ((p[1] << 8) | p[0]));
+       return (p[0] | (__CAST(uint16_t, p[1]) << 8));
 }
 
 static __inline void __unused
@@ -288,7 +288,7 @@
 {
        const uint8_t *p = __CAST(const uint8_t *, buf);
 
-       return ((p[0] << 24) | (p[1] << 16) | (p[2] << 8) | p[3]);
+       return ((__CAST(uint32_t, be16dec(p)) << 16) | be16dec(p + 2));
 }
 
 static __inline uint32_t __unused
@@ -296,7 +296,7 @@
 {
        const uint8_t *p = __CAST(const uint8_t *, buf);
 
-       return ((p[3] << 24) | (p[2] << 16) | (p[1] << 8) | p[0]);
+       return (le16dec(p) | (__CAST(uint32_t, le16dec(p + 2)) << 16));
 }
 
 static __inline void __unused