Christopher Currie wrote:
As a compromise, we could create lock_transfer<> objects that wouldn't lock a mutex, but would allow initialization syntax in places where the language makes it difficult (this is just a quick sketch, there may be errors):
<code snipped> This won't work. Try to compile this with Comeau online: struct lock_transfer {}; struct scoped_lock { scoped_lock( lock_transfer ) {} private: scoped_lock( scoped_lock const & ); scoped_lock & operator =( scoped_lock const & ); }; int main() { scoped_lock l = lock_transfer(); return 0; } You'll get: "ComeauTest.c", line 13: error: "scoped_lock::scoped_lock(const scoped_lock &)", required for copy that was eliminated, is inaccessible scoped_lock l = lock_transfer(); ^ Non-copyable types can't be initialized this way. The code I posted earlier worked around this problem by enabling just enough move semantics to allow a lock to be returned from a function, but nothing else. The lock is still non-copyable. -- Eric Niebler Boost Consulting www.boost-consulting.com