求高手解答关于typeid的问题

[ganmaojiushijiu]

#include<typeinfo>
#include<iostream>

using namespace std;

struct A{virtual ~A(){}};
struct B:A {};
struct C{};
struct D:C{D(int) {}};

int main()
{
B b;
A *a=&b;

cout<<typeid(b).name()<<endl;
cout<<typeid(*a).name()<<endl; //这里为什么输出的是struct B？
cout<<boolalpha<<(typeid(*a)==typeid(b))<<endl;
cout<<(typeid(A)==typeid(const A))<<endl;

D d(1);
C *c=&d;

cout<<typeid(d).name()<<endl;
cout<<typeid(*c).name()<<endl; //而这里为什么输出的是 struct C呢？
cout<<boolalpha<<(typeid(d)==typeid(*c))<<endl;
//cout<<(typeid(D)==typeid(const D))<<endl;

int i;

cout<<typeid(i).name()<<endl;

return 0;
}

问题已经在代码中问出求高手解答

[iamnobody]

简单说,多态类和非多态类是不一样的.

[titer1]

[Quote=引用 2 楼 的回复:]

typeid
========
5.2.8 Type identification [expr.typeid]
2 When typeid is applied to an lvalue expression whose type is a polymorphic class type (10.3), the result
refers to a type_info object re……
[/Quote]

抓住英文解释中的the most derived object 。。

[Gloveing]

c++中，struct可以看做是特殊的class

这就是所谓的：虚函数，动态绑定 问题

[iamnobody]

typeid
========
5.2.8 Type identification [expr.typeid]
2 When typeid is applied to an lvalue expression whose type is a polymorphic class type (10.3), the result
refers to a type_info object representing the type of the most derived object (1.8) (that is, the dynamic
type) to which the lvalue refers. If the lvalue expression is obtained by applying the unary * operator to a
pointer62) and the pointer is a null pointer value (4.10), the typeid expression throws the bad_typeid
exception (18.5.3).