On Jun 3, 2011, at 12:50 AM, Chandler Carruth wrote:
> This patch should catch more integer shift left undefined behavior according
> to C and C++ standard semantics. Specifically it should catch the case where
> a signed integer type when shifted is no longer representable in the result
> type.
Very cool.
> There are some general cleanups that can be made to the existing undefined
> behavior check here given the this change, but I just wanted to add
> functionality here. Let me know if I should just commit freely when adding
> these types of checks (provided proper testing and certainty that the
> behavior is in fact undefined). Also any guidance on other languages or specs
> I should be checking prior to enabling such checks (Currently looking at C99,
> C++98, C++03, and C++0x) would be welcome.
This is John's domain, but LGTM.
> Finally, the testcase is a bit lame. I'd really like to test this by creating
> sources that exhibit the undefined behavior being checked, compile and run
> them verifying crash and non-crash inputs. Is that do-able in the current
> test harness? Seems unlikely, but if folks have ideas I'm all ears.
Clang's test harness can't handle this, but you could add these tests to
nightlytest.
- Doug
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