[libcxx] Provide thread annotations for shared_mutex

[phosek]

Summary

shared_mutex was introduced in C++17 but its implementation currently
doesn't use Clang's thread annotations like regular mutex. This change
adds those.

[ldionne]

libcxx/include/shared_mutex

164 ↗

(On Diff #173265)

Just making sure; those are only needed on the declarations?

[phosek]

libcxx/include/shared_mutex

164 ↗

(On Diff #173265)

Yes

[aaronpuchert]

Shouldn't the attributes be on shared_mutex and shared_timed_mutex, respectively, instead of the internal __shared_mutex_base? Note that the analysis is strictly intraprocedural and doesn't do "inlining".

libcxx/trunk/include/shared_mutex

 #endif
 
 #ifdef _LIBCPP_HAS_NO_THREADS
 #error <shared_mutex> is not supported on this single threaded system
 #else // !_LIBCPP_HAS_NO_THREADS
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-struct _LIBCPP_TYPE_VIS _LIBCPP_AVAILABILITY_SHARED_MUTEX __shared_mutex_base
+struct _LIBCPP_TYPE_VIS _LIBCPP_AVAILABILITY_SHARED_MUTEX _LIBCPP_THREAD_SAFETY_ANNOTATION(capability("shared_mutex"))
+__shared_mutex_base
 {
     mutex               __mut_;
     condition_variable  __gate1_;
     condition_variable  __gate2_;
     unsigned            __state_;
 
     static const unsigned __write_entered_ = 1U << (sizeof(unsigned)*__CHAR_BIT__ - 1);
     static const unsigned __n_readers_ = ~__write_entered_;
 
     __shared_mutex_base();
     _LIBCPP_INLINE_VISIBILITY ~__shared_mutex_base() = default;
 
     __shared_mutex_base(const __shared_mutex_base&) = delete;
     __shared_mutex_base& operator=(const __shared_mutex_base&) = delete;
 
     // Exclusive ownership
-    void lock(); // blocking
-    bool try_lock();
-    void unlock();
+    void lock() _LIBCPP_THREAD_SAFETY_ANNOTATION(acquire_capability()); // blocking
+    bool try_lock() _LIBCPP_THREAD_SAFETY_ANNOTATION(try_acquire_capability(true));
+    void unlock() _LIBCPP_THREAD_SAFETY_ANNOTATION(release_capability());
 
     // Shared ownership
-    void lock_shared(); // blocking
-    bool try_lock_shared();
-    void unlock_shared();
+    void lock_shared() _LIBCPP_THREAD_SAFETY_ANNOTATION(acquire_shared_capability()); // blocking
+    bool try_lock_shared() _LIBCPP_THREAD_SAFETY_ANNOTATION(try_acquire_shared_capability(true));
+    void unlock_shared() _LIBCPP_THREAD_SAFETY_ANNOTATION(release_shared_capability());
 
 //     typedef implementation-defined native_handle_type; // See 30.2.3
 //     native_handle_type native_handle(); // See 30.2.3
 };
 
 
 #if _LIBCPP_STD_VER > 14
 class _LIBCPP_TYPE_VIS _LIBCPP_AVAILABILITY_SHARED_MUTEX shared_mutex