将shared_ptr分配给weak_ptr [英] Assigning shared_ptr to weak_ptr

问题描述

我想将构造的shared_ptr分配给weak_ptr:

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); });

但是，当我执行rw.expired()时，它显示已过期，表示它为空.有什么建议可以解决我的问题吗?

But, when I do rw.expired(), it shows expired means it is empty. Any suggestions where I am going wrong?

谢谢.

推荐答案

std::shared_ptr的目的是在指向该对象的最后一个共享指针被破坏或重新分配给其他地方时释放托管对象.您创建了一个临时共享的ptr，将其设置为std::weak_ptr，然后在表达式末尾将其销毁.您需要保持它的生命:

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;

现在rw至少在shared仍然存在时不会过期.

now rw would not expire at least while shared is still alive.

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