1 files changed, 13 insertions, 7 deletions
diff --git a/src/corelib/thread/qmutex.h b/src/corelib/thread/qmutex.h
index 12987f16c3..7cda53db5f 100644
--- a/src/corelib/thread/qmutex.h
+++ b/src/corelib/thread/qmutex.h
@@ -67,6 +67,12 @@ class QMutexData;
 class Q_CORE_EXPORT QBasicMutex
 {
 public:
+#ifdef Q_COMPILER_CONSTEXPR
+    constexpr QBasicMutex()
+        : d_ptr(nullptr)
+    {}
+#endif
+
     // BasicLockable concept
     inline void lock() QT_MUTEX_LOCK_NOEXCEPT {
         if (!fastTryLock())
@@ -92,16 +98,16 @@ public:
 
 private:
     inline bool fastTryLock() Q_DECL_NOTHROW {
-        return d_ptr.testAndSetAcquire(Q_NULLPTR, dummyLocked());
+        return d_ptr.testAndSetAcquire(nullptr, dummyLocked());
     }
     inline bool fastTryUnlock() Q_DECL_NOTHROW {
-        return d_ptr.testAndSetRelease(dummyLocked(), Q_NULLPTR);
+        return d_ptr.testAndSetRelease(dummyLocked(), nullptr);
     }
     inline bool fastTryLock(QMutexData *&current) Q_DECL_NOTHROW {
-        return d_ptr.testAndSetAcquire(Q_NULLPTR, dummyLocked(), current);
+        return d_ptr.testAndSetAcquire(nullptr, dummyLocked(), current);
     }
     inline bool fastTryUnlock(QMutexData *&current) Q_DECL_NOTHROW {
-        return d_ptr.testAndSetRelease(dummyLocked(), Q_NULLPTR, current);
+        return d_ptr.testAndSetRelease(dummyLocked(), nullptr, current);
     }
 
     void lockInternal() QT_MUTEX_LOCK_NOEXCEPT;
@@ -133,7 +139,7 @@ public:
     // Lockable concept
     bool try_lock() QT_MUTEX_LOCK_NOEXCEPT { return tryLock(); }
 
-#if QT_HAS_INCLUDE(<chrono>)
+#if QT_HAS_INCLUDE(<chrono>) || defined(Q_CLANG_QDOC)
     // TimedLockable concept
     template <class Rep, class Period>
     bool try_lock_for(std::chrono::duration<Rep, Period> duration)
@@ -251,7 +257,7 @@ class Q_CORE_EXPORT QMutex
 public:
     enum RecursionMode { NonRecursive, Recursive };
 
-    inline explicit QMutex(RecursionMode mode = NonRecursive) Q_DECL_NOTHROW { Q_UNUSED(mode); }
+    inline Q_DECL_CONSTEXPR explicit QMutex(RecursionMode = NonRecursive) Q_DECL_NOTHROW { }
 
     inline void lock() Q_DECL_NOTHROW {}
     inline bool tryLock(int timeout = 0) Q_DECL_NOTHROW { Q_UNUSED(timeout); return true; }
@@ -287,7 +293,7 @@ public:
 
     inline void unlock() Q_DECL_NOTHROW {}
     void relock() Q_DECL_NOTHROW {}
-    inline QMutex *mutex() const Q_DECL_NOTHROW { return Q_NULLPTR; }
+    inline QMutex *mutex() const Q_DECL_NOTHROW { return nullptr; }
 
 private:
     Q_DISABLE_COPY(QMutexLocker)