c++引入额外开销的情况

#include<iostream>

#include<typeinfo>

using namespace std;

class base

{

public:

virtual void funcA()

{

cout << "base" << endl;

}

};

class derived :public base

{

public:

virtual void funcB()

{

cout << "derived" << endl;

}

};

void funcC(base* p)

{

derived *dp = dynamic_cast<derived *>(p);

if (dp != NULL)

{

dp->funcB();

}

else

{

p->funcA();

}

}

//funcD用typeid操作符

void funcD(base *p)

{

derived* dp = NULL;

if (typeid(*p) == typeid(derived))

{

dp = static_cast<derived*>(p);

dp->funcB();

}

else

p->funcA();

}

int main()

{

base *cp = new derived;

cout << typeid(cp).name() << endl;

cout << typeid(*cp).name() << endl;

funcD(cp);

funcC(cp);

base *dp = new base;

funcC(dp);

funcD(dp);

system("pause");

return 0;

}

运行结果为：

class  base *

class derived

derived

derived

base

base

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