32 Thread support library [thread]

32.5 Mutual exclusion [thread.mutex]

32.5.5 Locks [thread.lock]

32.5.5.3 Class template scoped_­lock [thread.lock.scoped]

namespace std { template<class... MutexTypes> class scoped_lock { public: using mutex_type = see below; // Only if sizeof...(MutexTypes) == 1 is true explicit scoped_lock(MutexTypes&... m); explicit scoped_lock(adopt_lock_t, MutexTypes&... m); ~scoped_lock(); scoped_lock(const scoped_lock&) = delete; scoped_lock& operator=(const scoped_lock&) = delete; private: tuple<MutexTypes&...> pm; // exposition only }; }
An object of type scoped_­lock controls the ownership of lockable objects within a scope.
A scoped_­lock object maintains ownership of lockable objects throughout the scoped_­lock object's lifetime.
The behavior of a program is undefined if the lockable objects referenced by pm do not exist for the entire lifetime of the scoped_­lock object.
  • If sizeof...(MutexTypes) is one, let Mutex denote the sole type constituting the pack MutexTypes.
    Mutex shall meet the Cpp17BasicLockable requirements ([thread.req.lockable.basic]).
    The member typedef-name mutex_­type denotes the same type as Mutex.
  • Otherwise, all types in the template parameter pack MutexTypes shall meet the Cpp17Lockable requirements ([thread.req.lockable.req]) and there is no member mutex_­type.
explicit scoped_lock(MutexTypes&... m);
Preconditions: If a MutexTypes type is not a recursive mutex, the calling thread does not own the corresponding mutex element of m.
Effects: Initializes pm with tie(m...).
Then if sizeof...(MutexTypes) is 0, no effects.
Otherwise if sizeof...(MutexTypes) is 1, then m.lock().
Otherwise, lock(m...).
explicit scoped_lock(adopt_lock_t, MutexTypes&... m);
Preconditions: The calling thread owns all the mutexes in m.
Effects: Initializes pm with tie(m...).
Throws: Nothing.
~scoped_lock();
Effects: For all i in [0, sizeof...(MutexTypes)), get<i>(pm).unlock().