问题
I want to assign constructed shared_ptr to weak_ptr:
std::weak_ptr<void> rw = std::shared_ptr<void>(operator new(60), [](void *pi) { operator delete(pi); });
But, when I do rw.expired(), it shows expired means it is empty. Any suggestions where I am going wrong?
Thanks in advance.
回答1:
Purpose of std::shared_ptr is to release managed object when last shared pointer which points to it is destroyed or reassigned to somewhere else. You created a temporary shared ptr, assgned it to std::weak_ptr and then it is just destroyed at the end of the expression. You need to keep it alive:
auto shared = std::shared_ptr<void>(operator new(60), [](void *pi) { operator delete(pi); });
std::weak_ptr<void> rw = shared;
now rw would not expire at least while shared is still alive.
来源：https://stackoverflow.com/questions/55214440/assigning-shared-ptr-to-weak-ptr