1 From e6735556ed0a5e791ea81a015a90c130a0eea060 Mon Sep 17 00:00:00 2001
2 From: Xi Wang <xi@mit.edu>
3 Date: Wed, 20 Feb 2013 12:45:45 -0500
4 Subject: [PATCH] nice: fix overflow checking in int_add_no_wrap()
6 In C, signed integer overflow is undefined behavior. Many compilers
7 optimize away checks like `a + b < a'.
9 Use safe precondition testing instead.
11 Signed-off-by: Xi Wang <xi@mit.edu>
12 Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>
14 libc/sysdeps/linux/common/nice.c | 10 +++++-----
15 1 file changed, 5 insertions(+), 5 deletions(-)
17 diff --git a/libc/sysdeps/linux/common/nice.c b/libc/sysdeps/linux/common/nice.c
18 index 3694db8..ed39946 100644
19 --- a/libc/sysdeps/linux/common/nice.c
20 +++ b/libc/sysdeps/linux/common/nice.c
21 @@ -25,15 +25,15 @@ static __inline__ _syscall1(int, __syscall_nice, int, incr)
23 static __inline__ int int_add_no_wrap(int a, int b)
28 - if (s > a) s = INT_MIN;
29 + if (a < INT_MIN - b)
32 - if (s < a) s = INT_MAX;
33 + if (a > INT_MAX - b)
41 static __inline__ int __syscall_nice(int incr)