aaron.ballman added a comment. In D66364#1633775 <https://reviews.llvm.org/D66364#1633775>, @rsmith wrote:
> `_Thread_local` is a reserved identifier; we generally don't produce > extension warnings for uses of reserved identifiers. (Eg, there's no warning > for `_Atomic` in C++ or `_Bool` in C89, and no warning for uses of > `__type_traits` or `__builtins`.) > > But I note that we *do* warn for some of these already (eg, `_Generic`, > `_Static_assert`, `_Alignas`, and `_Alignof` get a warning). We should choose > a rule and apply it consistently. > > What's the motivation for warning on this? Maybe that can inform whether > these warnings are useful in general. My motivation is for portability. _Thread_local (and all the rest) do not exist in C99 or earlier (or C++), so having some way to warn users of that is useful. I agree that we should be consistent and go with all or none, but my preference is for all (esp since this is a -pedantic warning class). That said, I think `__builtins` and `__type_traits` are a separate question, and a somewhat interesting one. I could see some value in a pedantic warning for use of a reserved identifier which is an implementation detail outside of a system header in theory, but I'm not entirely sure what such a diagnostic would look like in practice. Is `__clang__` an implementation detail? I don't think we should warn on uses of it! What about `_UNICODE` when working with MSVC compat? Same situation. Rather than try to answer that question, I think I draw the line with only pedantically warning on reserved identifiers in the standard. WDYT? Repository: rC Clang CHANGES SINCE LAST ACTION https://reviews.llvm.org/D66364/new/ https://reviews.llvm.org/D66364 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
