erik.pilkington added a comment.
In D63856#1560180 <https://reviews.llvm.org/D63856#1560180>, @rjmccall wrote:
> This only applies to relational operators, right? I'm a little uncomfortable
> with calling this "tautological" since it's not like it's *undefined
> behavior* to have `(BOOL) 2`, it's just *unwise*. But as long as we aren't
> warning about reasonable idioms that are intended to handle unfortunate
> situations — like other code that might have left a non-`{0,1}` value in the
> `BOOL` — I think this is fine.
I think the party line is that it is undefined behaviour (in some sense), since
UBSan will happily crash if you try to load a non-boolean value from a BOOL. It
is a bit unfortunate that "defensive" code will start warning here though :/.
Maybe we can try to detect and permit something like `B < NO || B > YES`, or
emit a note with some canonical way of checking for non-boolean BOOLs. Even if
we end up having to disable it default, I think its still a good diagnostic to
have. A warning on stores to BOOL would probably be a lot higher value, though.
Repository:
rC Clang
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https://reviews.llvm.org/D63856/new/
https://reviews.llvm.org/D63856
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