Technical Answers Preliminary Understanding of Object-Oriented (C++ Class)

We should know that C has two kinds of member data: static, nostatic; three kinds of member functions: static, nostatic, virtual. In fact, for ordinary member functions, there is a this pointer in the parameter. This this pointer actually points to the object itself, through this pointer. The C compiler will know which object calls the member function of the class.

Are the member variables and member functions in C class objects stored together? if not?

We should know that C has two kinds of member data: static, nostatic; three kinds of member functions: static, nostatic, virtual.
Look at this case below:

class A
{    int a;    int b;
};class B
{    int a;    int b;    static int c;
};class C
{    int a;    int b;    static int c;public:    void func() {}    static void pg() {}
};int main()
{    //1. 分析A对象占的内存
    A a;    cout << sizeof(a) << endl;  //结果是8

    //2. 分析B对象占的内存
    B b;    cout << sizeof(b) << endl;  //结果是8

    //3. 分析C对象占的内存
    C c;    cout << sizeof(c) << endl;  //结果是8

    return 0;
}

In fact, based on the output results, we draw the following conclusions:
a. Member variables:

• Ordinary members Variables are stored in objects and have the same memory layout and byte alignment as strutc variables;

• Static member variables are stored in the global data area

b. Member functions are stored in code segments.

How does the C compiler manage classes and objects? Specifically, the object calls methods in the class. How does the C compiler distinguish which specific object calls which member method?

In fact, for ordinary member functions (not static member functions), there is a this pointer in the parameter. This this pointer actually points to the object itself, through this pointer. The C compiler will know which object calls the member function of the class.

Let’s summarize:
a. Member variables and member functions in class C objects are stored separately;
b. Ordinary member functions of class C (including constructors, but (excluding static member functions) all contain a this pointer pointing to the current object;
c. Static member functions and static member variables belong to the class;
d. The difference between static member functions and ordinary member functions:
Static member functions do not contain a this pointer pointing to a specific object, while ordinary member functions contain a pointer pointing to a specific object.

Article Overview

We need to solve these problems:
a. Are member variables and member functions in class C objects stored together? if not?
b. How does the C compiler manage classes and objects? Specifically, the object calls methods in the class. How does the C compiler distinguish which specific object calls which member method?

Are member variables and member functions in class C objects stored together? if not?

We should know that C has two kinds of member data: static, nostatic; three kinds of member functions: static, nostatic, virtual.
Look at this case below:

class A
{    int a;    int b;
};class B
{    int a;    int b;    static int c;
};class C
{    int a;    int b;    static int c;public:    void func() {}    static void pg() {}
};int main()
{    //1. 分析A对象占的内存
    A a;    cout << sizeof(a) << endl;  //结果是8

    //2. 分析B对象占的内存
    B b;    cout << sizeof(b) << endl;  //结果是8

    //3. 分析C对象占的内存
    C c;    cout << sizeof(c) << endl;  //结果是8

    return 0;
}

In fact, based on the output results, we draw the following conclusions:
a. Member variables:

• Ordinary members Variables are stored in objects and have the same memory layout and byte alignment as strutc variables;

• Static member variables are stored in the global data area

b. Member functions are stored in code segments.

How does the C compiler manage classes and objects? Specifically, the object calls methods in the class. How does the C compiler distinguish which specific object calls which member method?

In fact, for ordinary member functions (not static member functions), there is a this pointer in the parameter. This this pointer actually points to the object itself, through this pointer. The C compiler will know which object calls the member function of the class.

Let’s summarize:
a. Member variables and member functions in class C objects are stored separately;
b. Ordinary member functions of class C (including constructors, but (excluding static member functions) all contain a this pointer pointing to the current object;
c. Static member functions and static member variables belong to the class;
d. The difference between static member functions and ordinary member functions:
Static member functions do not contain a this pointer pointing to a specific object, while ordinary member functions contain a pointer pointing to a specific object.

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