[PATCH] D122874: [clang] Add GNU spelling for no_unqiue_address attribute

Nikolas Klauser via Phabricator via cfe-commits cfe-commits at lists.llvm.org
Tue Apr 5 13:34:14 PDT 2022

philnik added a subscriber: ldionne.
philnik added a comment.

> And if `[[msvc::no_unique_address]]` and `[[no_unique_address]]` (when eventually implemented) in MSVC have a different ABI impact, will we will leave `__attribute__((no_unique_address))` alone so it won't break ABI?

I think that would depend on how Microsoft breaks the ABI. If there would be different mangling it would probably be best to also break the ABI of `__attribute__((no_unique_address))`, and I think that would be the most likely scenario.

> I believe we care about ABI stability, even on Windows. At the very least, I've never heard that the community does not care about ABI stability on Windows.

Sorry, with 'we' I meant libc++. Because libc++ is never the primary c++ standard library on Windows most programs that use it ship their own version, so ABI stability isn't really an issue there. I think there is also a mingw environment with libc++, but IIRC there ABI stability was also more of a nice-to-have than an absolute need-to-have.

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