[libcxx-commits] [libcxx] [libc++] Introduce ABI sensitive areas to avoid requiring _LIBCPP_HIDE_FROM_ABI everywhere (PR #131156)

[Louis Dionne via libcxx-commits]

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ldionne wrote:

With the introduction of this mechanism, as you pointed out, it would be possible to introduce a symbol in the dylib while forgetting to use `_LIBCPP_BEGIN_EXPLICIT_ABI_ANNOTATIONS`. The unfortunate result of that would be that we're exporting a symbol from the dylib which contains an ABI tag, and we'd likely only notice when we rev up the libc++ version number and notice the ABI list test failing. That's not great.

I think we can guard against that issue by ensuring that our ABI list never contains an ABI tag. I'd like that safeguard to be introduced before we make the change in this patch.

https://github.com/llvm/llvm-project/pull/131156