Add means to handle negative capabilities in thread safety annotations

1 files changed, 7 insertions, 0 deletions

diff --git a/src/threadsafety.h b/src/threadsafety.h
index 942aa3fdcd..5f2c40bac6 100644
--- a/src/threadsafety.h
+++ b/src/threadsafety.h
@@ -60,6 +60,13 @@
 // and should only be used when sync.h Mutex/LOCK/etc are not usable.
 class LOCKABLE StdMutex : public std::mutex
 {
+public:
+#ifdef __clang__
+    //! For negative capabilities in the Clang Thread Safety Analysis.
+    //! A negative requirement uses the EXCLUSIVE_LOCKS_REQUIRED attribute, in conjunction
+    //! with the ! operator, to indicate that a mutex should not be held.
+    const StdMutex& operator!() const { return *this; }
+#endif // __clang__
 };
 
 // StdLockGuard provides an annotated version of std::lock_guard for us,