c++ - shared_from_this 与派生类

Question

我正在尝试使用 shared_from_this 函数创建指向 this 的共享指针。

#include <iostream>
#include <memory>

class foo {
public:
    virtual void method() {
        std::cerr << "foo::method()" << std::endl;
    }
};

class foo_derived : public foo, public std::enable_shared_from_this<foo> {
public:
    void method() override {
        auto self(shared_from_this());
        std::cerr << "foo_derived::method" << std::endl;
    }
};

int main() {
    foo_derived().method();
}

此代码从 auto self(shared_from_this()); 行抛出 bad_weak_ptr我认为问题在于 self 是在派生类中创建的。我正在寻找对此行为的解释，也希望看到一个有效的 shared_from_this 用法与派生类的示例。

Answer 1

与继承无关。调用method这种方式反而会起作用:std::make_shared<foo_derived>()->method();

cppreference std::enable_shared_from_this::shared_from_this

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).