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()

巴特西

C++中的复制构造函数

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