Add clang thread safety annotations to mutex and lock_guard. Patch by jamesr@google.com.

This adds clang thread safety annotations to std::mutex and
std::lock_guard so code using these types can use these types directly
instead of having to wrap the types to provide annotations. These checks
when enabled by -Wthread-safety provide simple but useful static
checking to detect potential race conditions.
See http://clang.llvm.org/docs/ThreadSafetyAnalysis.html for details.

This patch was reviewed in http://reviews.llvm.org/D14731.


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@263611 91177308-0d34-0410-b5e6-96231b3b80d8

include/__config

diff --git a/include/__config b/include/__config
index a62b2be..c360214 100644
--- a/include/__config
+++ b/include/__config
@@ -859,6 +859,11 @@
 #endif
 #endif
 
+#if (defined(_LIBCPP_ENABLE_THREAD_SAFETY_ANNOTATIONS) && defined(__clang__) \
+      && __has_attribute(acquire_capability))
+#define _LIBCPP_HAS_THREAD_SAFETY_ANNOTATIONS
+#endif
+
 #endif // __cplusplus
 
 #endif // _LIBCPP_CONFIG