[libcxx-commits] [libcxx] [libcxx] Make removed allocator members constexpr in C++20 (PR #69466)

[Ilya Biryukov via libcxx-commits]

ilya-biryukov wrote:

I totally see your point and I respect the decision to avoid introducing more non-standard behavior. However, I believe it should apply when someone introduces new flags (or, rather, does not introduce them if that's the policy). For existing flags that produce non-compliant modes, like this one, I do not see a problem with changing the behavior, especially when it moves the code closer to being standard-compliant.

We managed to postpone dealing with those breakages I mentioned above and switched to C++20 earlier, enabling experiments with coroutines while we keep grinding through the cleanups. Those issues I mentioned are not caused by the flag, they are a part of a cleanup when moving from C++17 to C++20. So this flag is still of overall benefit for us, allowing to move more gradually than a full switch from one major language version to another.

https://github.com/llvm/llvm-project/pull/69466