[libcxx] Address comments to fix build failures

Author: elhewaty

libcxx/include/__mutex/unique_lock.h

@@ -15,13 +15,16 @@
 #include <__memory/addressof.h>
 #include <__mutex/tag_types.h>
 #include <__system_error/throw_system_error.h>
+#include <__utility/move.h>
 #include <__utility/swap.h>
 #include <cerrno>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <class _Mutex>
@@ -74,7 +77,8 @@ class unique_lock {
   }
 
   _LIBCPP_HIDE_FROM_ABI unique_lock& operator=(unique_lock&& __u) _NOEXCEPT {
-    unique_lock{std::move(__u)}.swap(*this);
+    if (this != &__u)
+      unique_lock(std::move(__u)).swap(*this);
     return *this;
   }
 
@@ -163,5 +167,6 @@ inline _LIBCPP_HIDE_FROM_ABI void swap(unique_lock<_Mutex>& __x, unique_lock<_Mu
 }
 
 _LIBCPP_END_NAMESPACE_STD
+_LIBCPP_POP_MACROS
 
 #endif // _LIBCPP___MUTEX_UNIQUE_LOCK_H

libcxx/include/shared_mutex

@@ -138,6 +138,7 @@ template <class Mutex>
 #    include <__mutex/tag_types.h>
 #    include <__mutex/unique_lock.h>
 #    include <__system_error/throw_system_error.h>
+#    include <__utility/move.h>
 #    include <__utility/swap.h>
 #    include <cerrno>
 #    include <version>
@@ -340,7 +341,8 @@ public:
   }
 
   _LIBCPP_HIDE_FROM_ABI shared_lock& operator=(shared_lock&& __u) _NOEXCEPT {
-    shared_lock{std::move(__u)}.swap(*this);
+    if (this != &__u)
+      shared_lock(std::move(__u)).swap(*this);
     return *this;
   }