RFR: 8324833: Signed integer overflows in ABS [v3]

[Dean Long]

On Fri, 2 Feb 2024 09:47:28 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> See the details in the bug. I think current `ABS` implementation is beyond repair, and we should just switch to `uabs`.
>> 
>> Additional testing:
>>  - [x] Linux x86_64 fastdebug, `all` with `-ftrapv` (now fully passes!)
>>  - [x] Linux x86_64 fastdebug, `all`
>
> Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Touchups

The undefined behavior I was talking about is what abs(INT_MIN) returns on two's complement, and the problem with checked_cast is that checked_cast<int,uint>(0x80000000u) won't complain, because the bits match, but having the sign change to negative may not be what the caller wants, especially when using ABS.

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PR Comment: https://git.openjdk.org/jdk/pull/17617#issuecomment-1928053407