aaron.ballman added inline comments.
================ Comment at: docs/clang-tidy/checks/readability-implicit-bool-conversion.rst:77-78 -- boolean expression/literal to integer, +- boolean expression/literal to integer (conversion from boolean to a single + bit bitfield is explicitly allowed), ---------------- alexfh wrote: > malcolm.parsons wrote: > > aaron.ballman wrote: > > > I think it should only be allowed if the bit-field type is unsigned; > > > signed bit-fields with a single bit are inherently not portable because > > > you don't know if that bit represents a sign bit or a value bit (imagine > > > a sign and magnitude integer representation). > > > > > > C++20 is changing this by standardizing on two's complement, but earlier > > > versions of C++ (and currently, all versions of C) are still impacted, so > > > another approach is to gate this on the language standard mode that's in > > > effect. > > I think it's the responsibility of a compiler using sign and magnitude > > representation to warn about signed single bit bitfields. > I agree with Malcolm's argument. But if the concern is practical (i.e. if > there's a user of this check, who's working with such compiler), we can add > an option to enable the warning in this case. Any objections? I think LLVM only supports two's complement backends currently anyway, so this is probably fine as-is. It was more a reaction to "there is no information loss" because there is information loss with the integer value, even in two's complement. It seems like clang is missing a warning that could handle this, however. https://godbolt.org/z/34xXIQ Boolean assignments are a bit of a different beast in that the `bool` is converted to integer as either `0` or `1`, explicitly. It's a bit strange that you put in `true` (which would be converted to `1`) and get back out `-1` as the integer value, but it's not awful because of the usual "0 is false, nonzero is true" conversion behavior back to `bool`. Repository: rCTE Clang Tools Extra CHANGES SINCE LAST ACTION https://reviews.llvm.org/D54941/new/ https://reviews.llvm.org/D54941 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
