[git commit] nice: fix overflow checking in int_add_no_wrap()
Bernhard Reutner-Fischer
rep.dot.nop at gmail.com
Wed Feb 20 18:12:51 UTC 2013
commit: http://git.uclibc.org/uClibc/commit/?id=79cd5fb435d910233b1eb03c93c6ae05908ab42b
branch: http://git.uclibc.org/uClibc/commit/?id=refs/heads/master
In C, signed integer overflow is undefined behavior. Many compilers
optimize away checks like `a + b < a'.
Use safe precondition testing instead.
Signed-off-by: Xi Wang <xi at mit.edu>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop at gmail.com>
---
libc/sysdeps/linux/common/nice.c | 10 +++++-----
1 files changed, 5 insertions(+), 5 deletions(-)
diff --git a/libc/sysdeps/linux/common/nice.c b/libc/sysdeps/linux/common/nice.c
index 3694db8..ed39946 100644
--- a/libc/sysdeps/linux/common/nice.c
+++ b/libc/sysdeps/linux/common/nice.c
@@ -25,15 +25,15 @@ static __inline__ _syscall1(int, __syscall_nice, int, incr)
static __inline__ int int_add_no_wrap(int a, int b)
{
- int s = a + b;
-
if (b < 0) {
- if (s > a) s = INT_MIN;
+ if (a < INT_MIN - b)
+ return INT_MIN;
} else {
- if (s < a) s = INT_MAX;
+ if (a > INT_MAX - b)
+ return INT_MAX;
}
- return s;
+ return a + b;
}
static __inline__ int __syscall_nice(int incr)
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