EmptyCrate Software. Travel. Stuff.

Recently, while watching the GoingNative conference, I learned about the new std::shared_ptr helper function std::make_shared. In the talk Stephan T. Lavavej discusses the performance improvements they've made. It seems std::make_shared can save a few extra allocations and a bit of memory overhead. This can be significant if you dynamically create lots of objects.

Back in the real world I found myself wondering if boost supported this little gem for boost::shared_ptr. Seems it does. And has since 1.39.0 in 2009. How is it possible that I've overlooked this?

Example usage:

Instead of doing this:

boost::shared_ptr<MyClass> ptr(new MyClass(param1, param2));
std::shared_ptr<MyClass> ptr2(new MyClass(param1, param2));

Do this:

boost::shared_ptr<MyClass> ptr = boost::make_shared<MyCass>(param1, param2);
std::shared_ptr<MyClass> ptr2 = std::make_shared<MyClass>(param1, param2);

Where this really shines is if you have a function expecting a shared_ptr.

void somefunc(const std::shared_ptr<MyClass> &ptr);
 
// Instead of this:
somefunc(std::shared_ptr<MyClass>(new MyClass(param1, param2)));
 
// do this:
somefunc(std::make_shared<MyClass>(param1, param2));

Similar functions exist for the other types of smart pointers.

Related boost docs are here.