std :: allocate_shared，允许从自定义分配器和单个分配中分配共享指针引用计数

Question

Make shared improves performance using single allocation for reference count and object, is it possible to use custom allocator along with std::allocate_shared and still have one allocation, as per test code i have written its not happening: sample

I am aware of boost::intrusive, but it has additional code to be written and which can go wrong

Answer 1

with the help of some debugging found out that std::allocate_shared does what is expected, it allows you to make only one allocation for both your object as well as for reference counter.

below is corrected code: allocate shared

Here operator new is called exactly once for both std::make_shared and std::allocate_shared. Using this object pool can be created and you can have same efficiency expected from boost::intrusive_ptr which needs additional coding.