C++内存布局(一) 引子 虚继承

class A

{

public:

int a;

};

class B : virtual public A

{

public:

int b;

};

class C : virtual public A

{};

class D : public C, public B

{};

int _tmain(int argc, _TCHAR* argv[])

{

A x;

B y; // ----->这里为B时候内存是 下面1的情况

//D y; // ----->这里为D的时候y的内存如下2;

int a = 0, b = 0, c = 0;

y.b = 3;

y.a = 4;

int *y1 = (int*)(&y);

memcpy(&a, y1, 4);

memcpy(&b, y1 + 1, 4);

memcpy(&c, y1 + 2, 4);

cout << a << " " << b << " " << c <<" " << endl;

//system("pause"); //在此处加上断点

return 0;

}

1.

&y 0x0012fec0

&(y.b) 0x0012fec4

&(*(A*)(&y)) 0x0012fec8

&(*(A*)(&(y.a)) 0x0012fec8

2.

&y 0x0012febc

&(*(C*)(&y)) 0x0012febc

&(*(B*)(&y)) 0x0012fec0

&(y.b) 0x0012fec4

&(*(A*)(&(y.a)) 0x0012fec8

class A

{

public:

int a;

};

class B : virtual public A

{

public:

int b;

};

class C : virtual public A

{

public:

//int c; // 打开 3

};

class D : public C, public B

{

public:

//int d; // 打开 4

};

int _tmain(int argc, _TCHAR* argv[])

{

A x;

D y;

int a = 0, b = 0, c = 0;

y.b = 3;

y.a = 4;

int *y1 = (int*)(&y);

memcpy(&a, y1, 4);

memcpy(&b, y1 + 1, 4);

memcpy(&c, y1 + 2, 4);

cout << a << " " << b << " " << c <<" " << endl;

//system("pause"); //在此处加上断点

return 0;

}

3.

&(y.c) 0x0012febc

&y 0x0012feb8

&(*(C*)(&y)) 0x0012feb8

&(*(B*)(&y)) 0x0012fec0

&(y.b) 0x0012fec4

&(*(A*)(&(y.a)) 0x0012fec8

4.

&(y.d) 0x0012feb8

&y 0x0012feb4

&(*(C*)(&y)) 0x0012feb4

&(*(B*)(&y)) 0x0012febc

&(y.b) 0x0012fec0

&(y.c) 0x0012fec4

&(*(A*)(&(y.a)) 0x0012fec8