[GitHub] [arrow] bkietz commented on pull request #7341: ARROW-9022: [C++][Compute] Make Add function safe for numeric limits

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bkietz commented on pull request #7341:
URL: https://github.com/apache/arrow/pull/7341#issuecomment-638241193


   > we should use `(int8, int8) -> int16`
   
   I'm not sure that's desirable. For one thing this leads to inconsistent handling of 64 bit integer types, which are currently allowed to overflow (NB: that means this kernel includes undefined behavior for int64).
   
   There are a few other approaches we could take (ordered by personal preference):
   
   - define explicit overflow behavior for signed integer operands (for example if we declared that `add(i8(a), i8(b))` will always be equivalent to `i8(i16(a) + i16(b))` then we could instantiate only unsigned addition kernels)
   - raise an error on signed overflow
   - provide `ArithmeticOptions::overflow_behavior` and allow users to choose between these
   - require users to pass arguments which will not overflow
   
   @wesm ?
   
   This is probably nuanced enough to merit a mailing list discussion.


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