小结1



#include <iostream>
using namespace std;
class a
{
public:
    a(int x=0){this->x=x;}
    virtual void show(){}
    int x;
};
class b 
{
public: b(int y=0){this->y=y;}
    void show(){}
    int y;
};
class c:public a,public b
{
public:
    c(int x,int y,int z):a(x),b(y),z(z){}
    void show(){}
    int z;
};
int main()
{
    c cc(1,2,3);
    a *a1=&cc;
    b *b1=&cc;
    delete b1;
//    cout<<a1->x<<"  "<<b1->y<<endl;
    cout<<cc.x<<cc.y<<cc.z<<endl;
}

26     a *a1=&cc;
27     b *b1=&cc;
不要误以为a1和b1的地址是一样哦。

查看了汇编代码

 

56:       a *a1=&cc;
004015B6   lea         eax,[ebp-0Ch]
004015B9   mov         dword ptr [ebp-10h],eax
57:       b *b1=&cc;
004015BC   lea         ecx,[ebp-0Ch]
004015BF   test        ecx,ecx
004015C1   je          main+3Bh (004015cb)
004015C3   lea         edx,[ebp-8]
004015C6   mov         dword ptr [ebp-18h],edx
004015C9   jmp         main+42h (004015d2)
004015CB   mov         dword ptr [ebp-18h],0
004015D2   mov         eax,dword ptr [ebp-18h]
004015D5   mov         dword ptr [ebp-14h],eax

可知a1 和b1的地址经过编译器内部处理的！

27     b *b1=&cc;
该操作所连带的"必要this指针的调整"，必须在执行期完成。

b1向后调整了sizeof(a)个字节到b类的存储地址了。