On 09/30/2015 11:27 PM, Paolo Bonzini wrote:
On 29/09/2015 22:34, Eduardo Habkost wrote:Fix undefined behavior detected by clang runtime check: qemu/target-i386/cpu.c:1494:15: runtime error: left shift of 1 by 31 places cannot be represented in type 'int' While doing that, add extra parenthesis for clarity. Reported-by: Peter Maydell <peter.mayd...@linaro.org> Signed-off-by: Eduardo Habkost <ehabk...@redhat.com> --- target-i386/cpu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/target-i386/cpu.c b/target-i386/cpu.c index 2b914b2..6af6db9 100644 --- a/target-i386/cpu.c +++ b/target-i386/cpu.c @@ -1491,7 +1491,7 @@ static void report_unavailable_features(FeatureWord w, uint32_t mask) int i; for (i = 0; i < 32; ++i) { - if (1 << i & mask) { + if ((1UL << i) & mask) {1U is enough. Paolo ps: Ego ceterum censeo that these warnings are useless and uglify the code unnecessarily. But it looks like I'm in a minority so the patch is okay.
I totally agree. There are no ones-compliment machines anymore, and so the whole point of that "undefined" in the C standard is moot. Let's all accept that shifts of signed quantities do exactly what we expect.
Without looking, I don't suppose either compiler has a switch to disable just the shift part of ubsan?
r~
