C++一般類的記憶體分佈

一下都是在x64下進行的編譯

1、空類

2、無繼承、無虛擬函式類

3、無繼承、有虛擬函式類

4、有繼承、有虛擬函式類

C++繼承類的記憶體分佈

C++多重繼承時的記憶體分佈

#include <iostream>
using namespace std;

class A {
public:
    int a;
};

class B1 :  public A {
public:
    int b1;
};

class B2 :  public A {
public:
    int b2;
};

class
 
 C : public B1, public B2 {
public:
    int c1;
};

int main() {
    
    cout << "A_size=" << sizeof(A) << endl;
    cout << "B1_size=" << sizeof(B1) << endl;
    cout << "B2_size=" << sizeof(B2) << endl;
    cout << "C_size=" << sizeof
 
(C) << endl;
    cout << "end..." << endl;
    system("pause");
    return 0;
}

類A、B1、B2的記憶體分佈

類C的記憶體分佈

C++類虛繼承時的記憶體分佈---->虛繼承解決二義性的問題

#include <iostream>
using namespace std;

class A {
public:
    int a;
};

class B1 : virtual public A {
public:
    int b1;
};

 
class B2 : virtual public A {
public:
    int b2;
};

class C : public B1, public B2 {
public:
    int c1;
};

int main() {
    C  c1;
    c1.b1 = 100;
    c1.b2 = 200;
    c1.c1 = 300;

    c1.a = 500; //虛繼承使得成員變數a只有一份拷貝，通過虛指標可以確定地址

    cout << "A_size=" << sizeof(A) << endl;
    cout << "B1_size=" << sizeof(B1) << endl;
    cout << "B2_size=" << sizeof(B2) << endl;
    cout << "C_size=" << sizeof(C) << endl;
    cout << "end..." << endl;
    system("pause");
    return 0;
}

類A和B1的記憶體分佈

類B2的記憶體分佈

類C的記憶體分佈