C++核心准则C.127:包含虚函数的类应该有虚析构函数或保护析构函...
共 2293字，需浏览 5分钟
·
2020-02-01 23:23
独山玉雕件
C.127: A class with a virtual function should have a virtual or protected destructor
C.127:包含虚函数的类应该有虚析构函数或保护析构函数
Reason(原因)
A class with a virtual function is usually (and in general) used via a pointer to base. Usually, the last user has to call delete on a pointer to base, often via a smart pointer to base, so the destructor should be public and virtual. Less commonly, if deletion through a pointer to base is not intended to be supported, the destructor should be protected and nonvirtual; see C.35.
包含虚函数的类通常(大多数情况下)通过指向基类的指针使用。通常，最后一个使用者必须通过指向基类的指针调用delete操作，通常是指向基类的智能指针，因此析构函数应该是公开的虚函数。稍微特殊一些的情况是：如果不希望支持通过指向基类的指针销毁对象，析构函数应该是保护的非虚函数。参见C.35。
Example, bad(反面示例)
struct B {
virtual int f() = 0;
// ... no user-written destructor, defaults to public nonvirtual ...
};
// bad: derived from a class without a virtual destructor
struct D : B {
string s {"default"};
};
void use()
{
unique_ptr p = make_unique();
// ...
} // undefined behavior. May call B::~B only and leak the string
Note(注意)
There are people who don't follow this rule because they plan to use a class only through a shared_ptr: std::shared_ptr p = std::make_shared(args); Here, the shared pointer will take care of deletion, so no leak will occur from an inappropriate delete of the base. People who do this consistently can get a false positive, but the rule is important -- what if one was allocated using make_unique? It's not safe unless the author of B ensures that it can never be misused, such as by making all constructors private and providing a factory function to enforce the allocation with make_shared.
也有一些人计划只通过shared_ptr使用类：std::shared_ptr p=
std::make_shared
Enforcement(实施建议)
A class with any virtual functions should have a destructor that is either public and virtual or else protected and nonvirtual.
包含虚函数的类的析构函数要么是公开的虚函数，要么是保护的非虚函数。
Flag delete of a class with a virtual function but no virtual destructor.
提示针对包含虚函数却没有虚析构函数的类的销毁操作。
原文链接：
https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#enforcement-123
觉得本文有帮助？请分享给更多人。
关注【面向对象思考】轻松学习每一天！
面向对象开发，面向对象思考！