Bug 196829
| Summary: | Enable -fwrapv and /d2UndefIntOverflow | ||
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| Product: | WebKit | Reporter: | Yusuke Suzuki <ysuzuki> |
| Component: | JavaScriptCore | Assignee: | Yusuke Suzuki <ysuzuki> |
| Status: | NEW | ||
| Severity: | Normal | CC: | fujii.hironori, ysuzuki |
| Priority: | P2 | ||
| Version: | WebKit Nightly Build | ||
| Hardware: | Unspecified | ||
| OS: | Unspecified | ||
Yusuke Suzuki
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
| Attachments | ||
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| Add attachment proposed patch, testcase, etc. |
Yusuke Suzuki
Maybe, this would be my weekend task just for fun.