C++中的复制构造函数

与C++中的构造函数相同，复制构造函数在对象生成过程中同样进行插入对应的Vtable虚表，但在成员变量赋值时，除具有复制构造函数的成员对象外，编译器合成复制构造函数其余均采用”Bitwise copy semantics(位逐次拷贝)”语义实现对象成员的拷贝，无论处于何种语境。测试代码如下：

#include <iostream>
#include <string>
#include <cstdlib>
#include <cstring>

using namespace std;

class A {
private:
	char *str;
	int len;
public:
	A(const string &str) {
		this->str = (char *)(malloc(sizeof(char) * str.size()));
		len = str.size();
		memcpy(this->str,str.c_str(),len);
		cout << "A()" << endl;
	}

	A(const A&a) {
		if(this != &a) {

			if(this->str) delete this->str;

			string str(a.str);
			this->str = (char *)(malloc(sizeof(char) * str.size()));
			len = str.size();
			memcpy(this->str,str.c_str(),len);
			cout << "A(const A &a)" << endl;
		}
	}

	~A() {
		delete str;
		str = NULL;
		cout << "~A()" << endl;
	}
};

class B {
private:
	char *str;
	int len;
	string str_;
public:
	B(const string &str) {
		this->str = (char *)(malloc(sizeof(char) * str.size()));
		len = str.size();
		memcpy(this->str,str.c_str(),len);
		cout << "B()" << endl;
	}

	~B() {
		delete str;
		cout << "~B()" << endl;
	}
};


class C:public A {
private:
	char *str_;
	int len;
public:
	C(const string &str):A(str) {
		this->str_ = (char *)(malloc(sizeof(char) * str.size()));
		len = str.size();
		memcpy(this->str_,str.c_str(),len);
		cout << "C()" << endl;
	}

	~C() {
		delete str_;
		cout << "~C()" << endl;
	}
};

class D {
private:
	char *str_;
	int len;
public:
	D(const string &str) {
		this->str_ = (char *)(malloc(sizeof(char) * str.size()));
		len = str.size();
		memcpy(this->str_,str.c_str(),len);
		cout << "D()" << endl;
	}

	~D() {
		delete str_;
		cout << "~D()" << endl;
	}

	virtual void fun() {
		cout << "D::fun()" << endl;
	}

};

class E:public virtual D {

private:
	char *str_;
	int len;
public:
	E(const string &str):D(str) {
		this->str_ = (char *)(malloc(sizeof(char) * str.size()));
		len = str.size();
		memcpy(this->str_,str.c_str(),len);
		cout << "E()" << endl;
	}

	~E() {
		delete str_;
		cout << "~E()" << endl;
	}

	virtual void fun() {
		cout << "E::fun()" << endl;
	}
};


class F:public virtual D {

private:
	char *str_;
	int len;
public:
	F(const string &str):D(str) {
		this->str_ = (char *)(malloc(sizeof(char) * str.size()));
		len = str.size();
		memcpy(this->str_,str.c_str(),len);
		cout << "F()" << endl;
	}

	~F() {
		delete str_;
		cout << "~F()" << endl;
	}

	virtual void fun() {
		cout << "F::fun()" << endl;
	}
};


class G:public E,public F {

private:
	char *str_;
	int len;
public:
	G(const string &str):E(str),F(str),D(str) {
		this->str_ = (char *)(malloc(sizeof(char) * str.size()));
		len = str.size();
		memcpy(this->str_,str.c_str(),len);
		cout << "G()" << endl;
	}

	~G() {
		delete str_;
		cout << "~G()" << endl;
	}

	virtual void fun() {
		cout << "G::fun()" << endl;
	}
};

void fun(D *d)
{
	d->fun();
}

//static A a("classA");
//static B b("classB");
//static C c("classC");
//static E e("classE");
static G g("classG");
int main(int argc, char *argv[])
{
	//A a1 = a;
	//B b1 = b;
	//C c1 = c;
	//E d1 = e;
	E e1 = g;
	F f1 = g;
	fun(&e1);
	fun(&f1);
	//fun(&g);
	return 0;
}

 上面分别测试单继承，多继承，无继承，多态各种情况下，g++编译器合成复制构造函数的语义执行情况，未提供复制构造函数类成员均为”Bitwise Copy Semantics”语义，多态特性不受影响。

D()
E()
F()
G()
E::fun()
F::fun()
~F()
~D()
~E()
~D()
~G()
~F()
~E()
~D()