关于虚函数表那点事儿

class Base
{
public:
    Base(){}
    ~Base(){}

    void f0() {}
    void f1() {}
    void f2() {}
    void f3() {}

private:
    int a;
};

class Base    size(4):
    +---
 0  | a
    +---

class Base size(8):
    +---
 0  | {vfptr}
 4  | a
    +---

Base::$vftable@:
    | &Base_meta
    |  0
 0  | &Base::{dtor}

Base::{dtor} this adjustor: 0
Base::__delDtor this adjustor: 0
Base::__vecDelDtor this adjustor: 0

class Base
{
public:
    Base(){}
    virtual ~Base(){}

    virtual void f1() {}
    void f2() {}
    void f3() {}

private:
    int a;
};

class Sub : public Base
{
public:
    Sub() {}
    virtual ~Sub() {}

    virtual void f1() {} // 子类对f1提供新的实现

    virtual void g1() {}
    virtual void g2() {}
    virtual void g3() {}
    
private:
    int int_in_b2;
};

class Sub2 : public Sub
{
public:
    Sub2() {}
    virtual ~Sub2() {}

    virtual void h1() {}
    virtual void h2() {}
    virtual void h3() {}

    virtual void f1() {} // 子类对f1提供新的实现
    virtual void f2() {} // 子类对覆盖Base中的f1的实现
private:
    int int_in_b3;
};

class Base    size(8):
    +---
 0  | {vfptr}
 4  | a
    +---

Base::$vftable@:
    | &Base_meta
    |  0
 0  | &Base::{dtor}
 1  | &Base::f1

Base::{dtor} this adjustor: 0
Base::f1 this adjustor: 0
Base::__delDtor this adjustor: 0
Base::__vecDelDtor this adjustor: 0


class Sub    size(12):
    +---
    | +--- (base class Base)
 0  | | {vfptr}
 4  | | a
    | +---
 8  | int_in_b2
    +---

Sub::$vftable@:
    | &Sub_meta
    |  0
 0  | &Sub::{dtor}
 1  | &Sub::f1
 2  | &Sub::g1
 3  | &Sub::g2
 4  | &Sub::g3

Sub::{dtor} this adjustor: 0
Sub::f1 this adjustor: 0
Sub::g1 this adjustor: 0
Sub::g2 this adjustor: 0
Sub::g3 this adjustor: 0
Sub::__delDtor this adjustor: 0
Sub::__vecDelDtor this adjustor: 0


class Sub2    size(16):
    +---
    | +--- (base class Sub)
    | | +--- (base class Base)
 0  | | | {vfptr}
 4  | | | a
    | | +---
 8  | | int_in_b2
    | +---
12  | int_in_b3
    +---

Sub2::$vftable@:
    | &Sub2_meta
    |  0
 0  | &Sub2::{dtor}
 1  | &Sub2::f1
 2  | &Sub::g1
 3  | &Sub::g2
 4  | &Sub::g3
 5  | &Sub2::h1
 6  | &Sub2::h2
 7  | &Sub2::h3
 8  | &Sub2::f2

Sub2::{dtor} this adjustor: 0
Sub2::h1 this adjustor: 0
Sub2::h2 this adjustor: 0
Sub2::h3 this adjustor: 0
Sub2::f1 this adjustor: 0
Sub2::f2 this adjustor: 0
Sub2::__delDtor this adjustor: 0
Sub2::__vecDelDtor this adjustor: 0