// 理解虚函数在内存中的实现
#include
class Base
{
public:
Base() {printf("Base\n");}
virtual ~Base() {printf("~Base\n");}
public:
virtual void f() {printf("Base:f\n");}
virtual void g() {printf("Base:g\n");}
int m_nBase;
};
class Derive : public Base
{
public:
Derive() {printf("Derive\n");}
~Derive() {printf("~Derive\n");}
public:
void f() {printf("Derive:f\n");}
void g() {printf("Derive:g\n");}
int m_nDerive;
};
typedef void (*FUN)(void);
int main()
{
Base* pB = new Base;
Base* pD = new Derive;
int nB = sizeof(Base);
int nD = sizeof(Derive);
pB->f();
pD->f();
pB->g();
pD->g();
// 获取虚函数表的地址
int* pBvftab = (int*)*(int*)pB;
// 0为析构函数，1为f(),2为g()
FUN fBF = (FUN)*(pBvftab + 1);
fBF();
FUN fBG = (FUN)*(pBvftab + 2);
fBG();
int* pDvftab = (int*)*(int*)pD;
FUN fDF = (FUN)*(pDvftab + 1);
fDF();
FUN fDG = (FUN)*(pDvftab + 2);
fDG();
delete pB;
delete pD;
return 0;
}
虚函数表指针在内存中的最前面
运行结果图：
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