为什么调用shared_from_this会调用std :: terminate [英] Why calling shared_from_this calls std::terminate

问题描述

考虑以下代码：

class A : public std::enable_shared_from_this<A>
{
public:
     std::shared_ptr<A> f()
     {
          return shared_from_this();
     }
};

int main()
{
    A a;
    std::shared_ptr<A> ptr = a.f();
}

此代码在Visual Studio 2017中终止。我想我在这里做错了。谁能帮我这个？我想要一个由shared_from_this（）创建的shared_ptr。

This code terminated in Visual Studio 2017. I guess I am doing something wrong here. Can anyone help me with this? I want a shared_ptr on a created by shared_from_this().

推荐答案

因为 a 不是共享指针拥有的。来自 cppreference ：

Because a is not a owned by a shared pointer. From cppreference:

只允许在以前共享的对象上，即在std :: shared_ptr管理的对象上，调用shared_from_this。否则，该行为是不确定的（直到C ++ 17）（从C ++ 17开始，由默认构造的weak_this的shared_ptr构造函数引发）std :: bad_weak_ptr抛出。

It is permitted to call shared_from_this only on a previously shared object, i.e. on an object managed by std::shared_ptr. Otherwise the behavior is undefined (until C++17)std::bad_weak_ptr is thrown (by the shared_ptr constructor from a default-constructed weak_this) (since C++17).

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