[PATCH] D17950: Implement is_always_lock_free

[JF Bastien via cfe-commits]

jfb added inline comments.

================
Comment at: lib/Frontend/InitPreprocessor.cpp:465
@@ +464,3 @@
+  if (LangOpts.CPlusPlus1z) {
+    Builder.defineMacro("__cpp_lib_atomic_is_always_lock_free", "201603");
+  }
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rsmith wrote:
> This should be defined by the relevant library header, not by the compiler, to indicate the library actually provides the new symbol.
Ah yes, makes sense. Looks like libc++ doesn't do this for other library features yet so I'll add it there.

This patch would then just fix test/Lexer/cxx-features.cpp for C++17 support and have nothing to do with `is_always_lock_free`. It's probably better if I close this patch and open a new one in that case.


http://reviews.llvm.org/D17950