C ++中的虚拟默认析构函数 [英] Virtual Default Destructors in C++

问题描述

我有一大堆继承自基类(准则)的继承类(准则).这是criterion的代码

I've got a large set of inherited classes (criteria) which inherit from a base class (criterion). Here's criterion's code

class criterion
{
public:
    virtual unsigned __int32 getPriorityClass() const = 0;
    virtual BOOL include(fileData &file) const = 0;
    virtual void reorderTree() = 0;
    virtual unsigned int directoryCheck(const std::wstring& directory) const = 0;
    virtual std::wstring debugTree() const = 0;
};

从这一类派生的类的一些示例:

Some examples of derived classes from this one:

class fastFilter : public criterion
{
public:
    void reorderTree() {};
    unsigned int  directoryCheck(const std::wstring& /*directory*/) const { return DIRECTORY_DONTCARE; };
    unsigned __int32 getPriorityClass() const { return PRIORITY_FAST_FILTER; };
};

class isArchive : public fastFilter
{
public:
    BOOL include(fileData &file) const
    {
        return file.getArchive();
    }
    std::wstring debugTree() const
    {
        return std::wstring(L"+ ISARCHIVE\n");
    };
};

由于我这里根本没有析构函数，但这应该是基类，因此我需要插入一个空的虚拟析构函数，即这样吗?:

Since I don't have a destructor here at all, but yet this is supposed to be a base class, do I need to insert an empty virtual destructor, I.e. like this?:

virtual void ~criterion() = 0;

如果需要该虚拟析构函数声明，那么所有中间类也都需要一个吗? IE.上面的fastFilter也需要虚拟析构函数吗?

If that virtual destructor declaration is needed, do all intermediate classes need one as well? I.e. would fastFilter above need a virtual destructor as well?

推荐答案

是的-基类需要一个虚拟析构函数，即使它为空.如果不这样做，那么当delete通过基础指针/引用成为派生对象时，派生对象的成员对象将没有机会正确地销毁自己.

Yes - the base class needs a virtual destructor, even if it's empty. If that is not done, then when something delete's a derived object through a base pointer/reference, the derived object's member objects will not get a chance to destroy themselves properly.

派生类无需声明或定义自己的析构函数，除非它们需要除默认析构函数行为以外的其他东西.

Derived classes do not need to declare or define their own destructor unless they need something other than default destructor behavior.

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