On 07.08.2015 03:09, Marcel Ebmer wrote:
Hi Everyone,
What if you could do
std::mutex the_mutex; using Lock = std::unique_lock<std::mutex>; void f() { with(Lock{the_mutex}) { do_something(); do_other_thing(); } }
*...or...*
struct Pushed_matrix { Pushed_matrix() { glPushMatrix(); } ~Pushed_matrix() { glPopMatrix(); } };
void f() { with(Pushed_matrix{}) draw_something(); }
At C++Now (2015), I presented this idea of mine and a macro implementation (BOOST_WITH) in a lightning talk. Since reception was good and more serious than the talk itself, I continued to work on it. I would appreciate informal review and opinions:
I don't think this utility gives much compared to the naive macro-less solution: f() { { Lock lock{the_mutex}); do_something(); do_other_thing(); } do_something_without_a_lock(); } Also, your macro requires the type to be movable. This seems like a rather strong requirement. For instance, it won't work with lock_guard. If you really want to improve it you might want to use 'for' statement instead of 'if', something along these lines: template< typename T > struct with_value { T value; bool guard; }; #define BOOST_WITH(x)\ for (with_value<decltype(x)> w{x, true}; w.guard; w.guard=false) There is another limitation that is not so easy to lift - you cannot access the guard value from within the scope. For instance, you cannot use the lock to block on a condition variable.