Smart pointer shared_ PTR and weak_ Difference of PTR

weak_ptr To solve the problem shared_ptr The problem of circular quotation , Prevent bidirectional binding

1. share_ptr Example

Schematic diagram

It can be seen that , When ptr_a,ptr_b Release , Did not lead to A,B The construction of class .

2. Right up there Example improvements ：

Schematic diagram

At this time, both class objects are destructed , meanwhile ptr_a Of use_count by 2,ptr_b Of use_count by 1