Fix: overflow of signed integer results in undefined behaviour
authorJérémie Galarneau <jeremie.galarneau@efficios.com>
Tue, 3 May 2016 02:46:28 +0000 (22:46 -0400)
committerJérémie Galarneau <jeremie.galarneau@efficios.com>
Tue, 3 May 2016 19:42:43 +0000 (15:42 -0400)
commit8aaa05176231002977b5a84530bf5ab72b88e144
tree8db28ee83c3d8e42fa92693de68ea2957445259a
parentbfadaf1262452a3f84ab5d6ea8350235b0e99a2c
Fix: overflow of signed integer results in undefined behaviour

The expression "min_value = -((int64_t)1 << (size - 1))"

will result in a signed integer overflow when size is 64
((1ULL << 63) > LONG_MAX).

Note that larger sizes are unsupported and checked for in the setter.

Signed overflows result in undefined behaviour and llvm takes
advantage of this to optimize away the range check

"if (value < min_value || value > max_value) {"

Surprisingly, this was not catched by GCC, Coverity, scan-build or
cppcheck.

The fix consists in computing both bounds using an unsigned long long
type and, in the case of the lower bound, negating it (resulting in a
long long).

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
formats/ctf/writer/event-fields.c
This page took 0.040386 seconds and 4 git commands to generate.