[PATCH] D54814: Move internal usages of `alignof`/`__alignof` to use `_LIBCPP_ALIGNOF`.
Eric Fiselier via Phabricator
reviews at reviews.llvm.org
Wed Nov 21 14:39:37 PST 2018
EricWF created this revision.
EricWF added a reviewer: ldionne.
Herald added a subscriber: christof.
Starting in Clang 8.0 and GCC 8.0, `alignof` and `__alignof` return different values in same cases. Specifically `alignof` and `_Alignof` return the minimum alignment for a type, where as `__alignof` returns the preferred alignment. libc++ currently uses `__alignof` but means to use `alignof`. See llvm.org/PR39713
This patch introduces the macro `_LIBCPP_ALIGNOF` so we can control which spelling gets used.
This patch does not introduce any ABI guard to provide the old behavior with newer compilers. However, if we decide that is needed, this patch makes it trivial to implement.
I think we should commit this change immediately, and decide what we want to do about the ABI afterwards.
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