https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104948
--- Comment #13 from dagelf <coenraad at wish dot org.za> --- Yes, I seem to have had a hole in my head. Sorry. For reference, to summarise then: & returns only the bits that are the same (bitwise AND) (or the bits that are left after AND) (which will evaluate to true unless its 0 eg. (2 & 1) is false but (3 & 1) is true. && casts operands to bool, so anything nonzero becomes 1. (eg. (2 && 1) is true) && and & nonequivalence: https://godbolt.org/z/Yf5cxcKch So & and && are only interchangeable when operating on bool parameters, on anything else they each do something completely different. The fact that there's a warning is great. Perhaps its fine. But this is something so fundamental, it feels like no room for confusion should be left. In fact, the more I think about it, the more I am convinced that it should not be a warning, but an error, so -Werror is my new default. Although I would love to find counter examples, I would be willing to wager that && mixed with non bools, will almost always be done in error.
