[英]Assigning shared_ptr to weak_ptr
I want to assign constructed shared_ptr to weak_ptr:我想将构造的 shared_ptr 分配给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.但是,当我执行rw.expired()
,它显示 expired 意味着它是空的。 Any suggestions where I am going wrong?我哪里出错了有什么建议吗?
Thanks in advance.提前致谢。
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. std::shared_ptr
目的是在指向它的最后一个共享指针被销毁或重新分配给其他地方时释放托管对象。 You created a temporary shared ptr, assgned it to std::weak_ptr
and then it is just destroyed at the end of the expression.您创建了一个临时共享 ptr,将其分配给std::weak_ptr
,然后在表达式结束时将其销毁。 You need to keep it alive:你需要让它保持活力:
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.现在rw
至少在shared
还活着时不会过期。
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