Re: [boost] [thread] synchronized_value: value and move semantics

On 21/02/13 02:02, Vicente J. Botet Escriba wrote:

Hi,

boost::synchronized_value (not released yet [1][2][3]) is based on [4]. See below part of this paper adapted to the Boost.Thread interface.

Currently boost::synchronized_value is in addition Copyable and Swappable. I was wondering if it is worth adding value and move semantics to synchronized_value. Making it EqualityComparable, LessThanComparable and Movable if the underlying type satisfy these requirements will allow to store them on a Boost.Container/C++11 container.

Do you see something completely wrong with this addition? Has some of you had a need for this? Could you share the context?

Sorry, I'm a bit late to the party and not really answering the question. I can see the usefulness of synchronized_value for C++03, but not in C++11. It's just too easy to forget to call the synchronise() member: boost::synchronized_value synch_queue; if(!synch_queue->empty()) synch_queue->pop(); when was was meant was (excuse use of auto, I've become lazy): boost::synchronized_value synch_queue; { auto lock = synch_queue.synchronize(); if(!synch_queue->empty()) synch_queue->pop(); } This is neither safe or efficient (2 lock/unlocks). I think this should just not exist in C++11 and instead be replaced by something like monitor<T> described by Herb Sutter [1]: monitor synch_queue; queue([](std::queue& q) { if(!q.empty()) q.pop(); } Now we're safe and efficient (one lock/unlock per block). Since movability is a C++11 thing, can we have something harder to use incorrectly than synchronized_value for C++11? I guess my point is rather than C++11ifying synchronized_value, can we have monitor instead? Thoughts? Ben [1] http://channel9.msdn.com/Shows/Going+Deep/C-and-Beyond-2012-Herb-Sutter-Conc... From 0:40:00