[PATCH] D157572: [clang] Add `[[clang::library_extension]]` attribute

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added a comment.

> This allows standard libraries to mark symbols as extensions, so the compiler can generate extension warnings when they are used.

Huh, so this is basically the opposite of the `__extension__` macro (which is used to silence extension warnings)? I don't think we need to introduce a new attribute to do this, we already have `diagnose_if`. e.g., https://godbolt.org/z/a5ae4T56o would that suffice?


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  https://reviews.llvm.org/D157572/new/

https://reviews.llvm.org/D157572