philnik added a comment. In D133574#4051899 <https://reviews.llvm.org/D133574#4051899>, @aaron.ballman wrote:
> In D133574#4051782 <https://reviews.llvm.org/D133574#4051782>, @bkramer wrote: > >> GitHub finds around 1.9k instances of this pattern to compute `alignof`. >> There's a lot of duplicates and `#ifdefs` so the real number is going to be >> smaller, but it seems to be quite common. The annoying part is that there is >> no `_Alignof` in C99 so for many of those projects there is no easy fix. >> >> Can this be demoted to a warning? >> >> https://github.com/search?type=code&q=%2Foffsetof%5Cs*%5C%28%5Cs*struct%5Cs*%5C%7B%2F+lang%3Ac > > Adding clang-vendors/others with opinions on diagnostic severity because this > could be disruptive. > > 1. Yes, we can. > 2. Blarg. I have sympathy because the standard was unclear on this point for > so long. I don't have as much sympathy for "there's no easy fix" -- the code > is not portable as-is (it's UB), and Clang supports `_Alignof` in C99 and > earlier, so for Clang there is an easy fix. > 3. Instead, should we downgrade to a warning-defaults-to-error instead of > just a warning? That gives these folks a path forward while still making it > clear to users "don't do this." But if we think we won't reasonably be able > to turn this into an error, I think a warning is better. > 4. Alternatively, should we document that we support this as an extension and > only give an extension warning for it? > > Regardless, we need to either make a decision shortly or we should revert > these changes until after the Clang 16 branch and re-land after that to give > ourselves more time to make a decision. If we don't have an obvious "this is > the right approach" answer and an implementation by Jan 19 (next Thursday), I > think we should revert to give ourselves breathing room. I'm not a vendor, but another option would be to make it a warning-defaults-to-error and indicate that it will be promoted to an error in a few (2?) releases. That makes it less painful, but still make it an error eventually. I don't know if clang has done anything like this before though. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D133574/new/ https://reviews.llvm.org/D133574 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
