[PATCH] D32265: Add __CLANG_ATOMIC_<TYPE>_LOCK_FREE macros for use in MSVC compatibility mode.

[Eric Fiselier via Phabricator via cfe-commits]

EricWF added a comment.

In https://reviews.llvm.org/D32265#731709, @jfb wrote:

> Is it a goal to support Microsoft's STL with this? If so, how does MSVC's STL implement `is_always_lock_free` at the moment? CL 19 2017 RTW doesn't seem to have anything <https://godbolt.org/g/jQOxlu>? Presumably they'll have to do *something*.


The goal is to allow libc++ to implement`ATOMIC_<TYPE>_LOCK_FREE` on Windows using Clang. As you know libc++ currently uses the `__GCC_ATOMIC_FOO` macros, but those aren't available on Windows.

Also AFAIK MSVC leaves the implementation of atomics up to the library, not the frontend. So W/E MSVC's STL does it's likely not sane or desirable.


https://reviews.llvm.org/D32265