C++虚函数表实现机制以及用C语言对其进行的模拟实现

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class Base1
{
public:
    int base1_1;
    int base1_2;
};

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class Base1
{
public:
    int base1_1;
    int base1_2;

    void foo(){}
};

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class Base1
{
public:
    int base1_1;
    int base1_2;

    virtual void base1_fun1() {}
};

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void*        __fun[1] = { &Base1::base1_fun1 };
const void** __vfptr = &__fun[0];

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class Base1
{
public:
    int base1_1;
    int base1_2;

    virtual void base1_fun1() {}
    virtual void base1_fun2() {}
};

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void*        __fun[] = { &Base1::base1_fun1, &Base1::base1_fun2 };
const void** __vfptr = __fun[0];

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class Base1
{
public:
    int base1_1;
    int base1_2;

    virtual void base1_fun1() {}
    virtual void base1_fun2() {}
};

class Derive1 : public Base1
{
public:
    int derive1_1;
    int derive1_2;
};

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class Base1
{
public:
    int base1_1;
    int base1_2;

    virtual void base1_fun1() {}
    virtual void base1_fun2() {}
};

class Derive1 : public Base1
{
public:
    int derive1_1;
    int derive1_2;

    // 覆盖基类函数
    virtual void base1_fun1() {}
};

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class Base1
{
public:
    int base1_1;
    int base1_2;

    virtual void base1_fun1() {}
    virtual void base1_fun2() {}
};

class Derive1 : public Base1
{
public:
    int derive1_1;
    int derive1_2;

    virtual void derive1_fun1() {}
};

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Derive1 d1;
Derive1* pd1 = &d1;
pd1->derive1_fun1();

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pd1->derive1_fun1();
00825466  mov         eax,dword ptr [pd1]  
00825469  mov         edx,dword ptr [eax]  
0082546B  mov         esi,esp  
0082546D  mov         ecx,dword ptr [pd1]  
00825470  mov         eax,dword ptr [edx+8]  
00825473  call        eax

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class Base1
{
public:
    int base1_1;
    int base1_2;

    virtual void base1_fun1() {}
    virtual void base1_fun2() {}
};

class Base2
{
public:
    int base2_1;
    int base2_2;

    virtual void base2_fun1() {}
    virtual void base2_fun2() {}
};

// 多继承
class Derive1 : public Base1, public Base2
{
public:
    int derive1_1;
    int derive1_2;

    // 基类虚函数覆盖
    virtual void base1_fun1() {}
    virtual void base2_fun2() {}

    // 自身定义的虚函数
    virtual void derive1_fun1() {}
    virtual void derive1_fun2() {}
};

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Derive1 d1;
Derive1* pd1 = &d1;
pd1->derive1_fun2();

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pd1->derive1_fun2();
00995306  mov         eax,dword ptr [pd1]  
00995309  mov         edx,dword ptr [eax]  
0099530B  mov         esi,esp  
0099530D  mov         ecx,dword ptr [pd1]  
00995310  mov         eax,dword ptr [edx+0Ch]  
00995313  call        eax

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class Base1
{
public:
    int base1_1;
    int base1_2;
};

class Base2
{
public:
    int base2_1;
    int base2_2;

    virtual void base2_fun1() {}
    virtual void base2_fun2() {}
};

// 多继承
class Derive1 : public Base1, public Base2
{
public:
    int derive1_1;
    int derive1_2;

    // 自身定义的虚函数
    virtual void derive1_fun1() {}
    virtual void derive1_fun2() {}
};

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Derive1 d1;
Derive1* pd1 = &d1;
pd1->derive1_fun2();

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pd1->derive1_fun2();
012E4BA6  mov         eax,dword ptr [pd1]  
012E4BA9  mov         edx,dword ptr [eax]  
012E4BAB  mov         esi,esp  
012E4BAD  mov         ecx,dword ptr [pd1]  
012E4BB0  mov         eax,dword ptr [edx+0Ch]  
012E4BB3  call        eax

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&d1==0x~d4
&d1.Base1::__vfptr==0x~d4
&d1.base2_1==0x~d8
&d1.base2_2==0x~dc
&d1.base1_1==0x~e0
&d1.base1_2==0x~e4

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class Base1
{
public:
    int base1_1;
    int base1_2;
};

class Base2
{
public:
    int base2_1;
    int base2_2;
};

// 多继承
class Derive1 : public Base1, public Base2
{
public:
    int derive1_1;
    int derive1_2;

    // 自身定义的虚函数
    virtual void derive1_fun1() {}
    virtual void derive1_fun2() {}
};

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class Base1
{
public:
    int base1_1;
    int base1_2;

    virtual void base1_fun1() {}
    virtual void base1_fun2() {}
};

class Base2
{
public:
    int base2_1;
    int base2_2;
};

class Base3
{
public:
    int base3_1;
    int base3_2;

    virtual void base3_fun1() {}
    virtual void base3_fun2() {}
};

// 多继承
class Derive1 : public Base1, public Base2, public Base3
{
public:
    int derive1_1;
    int derive1_2;

    // 自身定义的虚函数
    virtual void derive1_fun1() {}
    virtual void derive1_fun2() {}
};

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class Base1
{
public:
    Base1() : base1_1(11) {}
    int base1_1;
    virtual void base1_fun1() {
        std::cout << "Base1::base1_fun1()" << std::endl;
    }
};

class Base2
{
public:
    Base2() : base2_1(21) {}
    int base2_1;
};

class Base3
{
public:
    Base3() : base3_1(31) {}
    int base3_1;
    virtual void base3_fun1() {
        std::cout << "Base3::base3_fun1()" << std::endl;
    }
};

class Derive1 : public Base1, public Base2, public Base3
{
public:
    Derive1() : derive1_1(11) {}
    int derive1_1;

    virtual void base3_fun1() {
        std::cout << "Derive1::base3_fun1()" << std::endl;
    }
    virtual void derive1_fun1() {
            std::cout << "Derive1::derive1_fun1()" << std::endl;
    }
};

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void foo(Base1* pb1, Base2* pb2, Base3* pb3, Derive1* pd1)
{
    std::cout << "Base1::\n"
        << "    pb1->base1_1 = " << pb1->base1_1 << "\n"
        << "    pb1->base1_fun1(): ";
    pb1->base1_fun1();

    std::cout << "Base2::\n"
        << "    pb2->base2_1 = " << pb2->base2_1
        << std::endl;

    std::cout << "Base3::\n"
        << "    pb3->base3_1 = " << pb3->base3_1 << "\n"
        << "    pb3->base3_fun1(): ";
    pb3->base3_fun1();

    std::cout << "Derive1::\n"
        << "    pd1->derive1_1 = " << pd1->derive1_1<< "\n"
        << "    pd1->derive1_fun1(): ";
    pd1->derive1_fun1();
    std::cout<< "    pd1->base3_fun1(): ";
    pd1->base3_fun1();
    
    std::cout << std::endl;
}

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Derive1 d1;
foo(&d1, &d1, &d1, &d1);

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struct CBase2
{
    int base2_1;
};

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struct CBase1
{
    void** __vfptr;
    int base1_1;
};

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struct CBase1_VFTable
{
    void(__stdcall* base1_fun1)(CBase1* that);
};

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void __stdcall base1_fun1(CBase1* that)
{
    std::cout << "base1_fun1()" << std::endl;
}

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struct CBase3
{
    void** __vfptr;
    int base3_1;
};

struct CBase3_VFTable
{
    void(__stdcall* base3_fun1)(CBase3* that);
};

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void __stdcall base3_fun1(CBase3* that)
{
    std::cout << "base3_fun1()" << std::endl;
}

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struct CDerive1
{
    CBase1 base1;
    CBase3 base3;
    CBase2 base2;

    int derive1_1;
};

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struct CBase1_CDerive1_VFTable
{
    void (__stdcall* base1_fun1)(CBase1* that);
    void(__stdcall* derive1_fun1)(CDerive1* that);
};

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struct CBase3_CDerive1_VFTable
{
    void(__stdcall* base3_fun1)(CDerive1* that);
};

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void __stdcall base3_derive1_fun1(CDerive1* that)
{
    std::cout << "base3_derive1_fun1()" << std::endl;
}

void __stdcall derive1_fun1(CDerive1* that)
{
    std::cout << "derive1_fun1()" << std::endl;
}

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// CBase1 的虚函数表
CBase1_VFTable __vftable_base1;
__vftable_base1.base1_fun1 = base1_fun1;

// CBase3 的虚函数表
CBase3_VFTable __vftable_base3;
__vftable_base3.base3_fun1 = base3_fun1;

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// CDerive1 和 CBase1 共用的虚函数表
CBase1_CDerive1_VFTable __vftable_base1_derive1;
__vftable_base1_derive1.base1_fun1 = base1_fun1;
__vftable_base1_derive1.derive1_fun1 = derive1_fun1;

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CBase3_CDerive1_VFTable __vftable_base3_derive1;
__vftable_base3_derive1.base3_fun1 = base3_derive1_fun1;

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CDerive1 d1;
d1.derive1 = 1;

d1.base1.base1_1 = 11;
d1.base1.__vfptr = reinterpret_cast<void**>(&__vftable_base1_derive1);

d1.base2.base2_1 = 21;

d1.base3.base3_1 = 31;
d1.base3.__vfptr = reinterpret_cast<void**>(&__vftable_base3_derive1);

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char* p = reinterpret_cast<char*>(&d1);
Base1* pb1 = reinterpret_cast<Base1*>(p + 0);
Base2* pb2 = reinterpret_cast<Base2*>(p + sizeof(CBase1) + sizeof(CBase3));
Base3* pb3 = reinterpret_cast<Base3*>(p + sizeof(CBase1));
Derive1* pd1 = reinterpret_cast<Derive1*>(p);

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foo(pb1, pb2, pb3, pd1);