Question

尝试使用std::shared_ptr转发std::static_pointer_cast时发生了段错误，其中派生类还包含std::weak_ptr。

这是一个MWE：

#include<iostream>                                                                                                                                                                                                  
#include<memory>                                                                                                                                                                                                    

struct Base {};                                                                                                                                                                                                     

struct Derived : Base                                                                                                                                                                                               
{                                                                                                                                                                                                                   
    std::weak_ptr<int> wp;                                                                                                                                                                                          
};                                                                                                                                                                                                                  

int main()                                                                                                                                                                                                          
{                                                                                                                                                                                                                   
    auto pB = std::make_shared<Base>();              // Create a pointer to Base class instance                                                                                                                     
    auto pD = std::static_pointer_cast<Derived>(pB); // Downcast this to a Derived class instance                                                                                                                   
    auto pint = std::make_shared<int>(0);            // Define a pointer to an integer                                                                                                                              

    std::cout << "assigning pint" << std::endl;                                                                                                                                                                     
    pD->wp = pint;                                   //Attempt to assign member of Derived                                                                                                                                                                 
    std::cout << "Did not segfault" << std::endl;                                                                                                                                                                   

    return 0;                                                                                                                                                                                                       
}

Answer 1

这编译和工作，但我不确定它是否'好'c ++ 11

#include<iostream>                                                                                                                                                                               
#include<memory>                                                                                                                                                                                 

struct Base {};                                                                                                                                                                                  

struct Derived : Base                                                                                                                                                                            
{                                                                                                                                                                                                
    Derived(std::shared_ptr<Base> b) : Base{*b} {}                                                                                                                                               
    std::weak_ptr<int> wp;                                                                                                                                                                       
};                                                                                                                                                                                               

int main()                                                                                                                                                                                       
{                                                                                                                                                                                                
    auto pB = std::make_shared<Base>();              // Create a pointer to Base class instance                                                                                                  
    auto pD = std::make_shared<Derived>(pB);                                                                                                                                                     
    auto pint = std::make_shared<int>(0);            // Define a pointer to an integer                                                                                                           

    std::cout << "assigning pint" << std::endl;                                                                                                                                                  
    pD->wp = pint;                                                                                                                                                                               
    std::cout << "Did not segfault" << std::endl;                                                                                                                                                

    return 0;                                                                                                                                                                                    
}

将shared_ptr向下转换为包含weak_ptr c ++ 11的派生类

1 个答案: