NEW 196829
Enable -fwrapv and /d2UndefIntOverflow 
https://bugs.webkit.org/show_bug.cgi?id=196829
Summary Enable -fwrapv and /d2UndefIntOverflow
Yusuke Suzuki
Reported 2019-04-11 14:29:27 PDT
We already see a bug caused by signed integer overflow UB. If it does not hurt performance, we should enable this option to avoid such an UB. Personally, I think this UB is one of the most common UBs resulting in an actual bug. An attempt making this behavior by default in the spec exists[1]. While the main focus of that proposal is accepted, "making signed overflow well-defined" is rejected. So we should enable -fwrapv / d2UndefIntOverflow manually in the WebKit side. > Status-quo If a signed operation would naturally produce a value that is not within the range of the result type, the behavior is undefined. > The author had hoped to make this well-defined as wrapping (the operations produce the same value bits as for the corresponding unsigned type), but WG21 had strong resistance against this. [1]: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0907r2.html
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Yusuke Suzuki
Comment 1 2019-04-11 15:15:40 PDT
Maybe, this would be my weekend task just for fun.
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