转自/article/37527.htm，感谢作者
#include "stdafx.h"
#include <iostream>
using namespace std;
class B
{
public:
B():data(0) //默认构造函数
{
cout << "Default constructor is called." << endl;
}
B(int i):data(i) //带参数的构造函数
{
cout << "Constructor is called." << data << endl;
}
B(B &b) // 复制（拷贝）构造函数
{
data = b.data; cout << "Copy Constructor is called." << data << endl;
}
B& operator = (const B &b) //赋值运算符的重载
{
this->data = b.data;
cout << "The operator \"= \" is called." << data << endl;
return *this;
}
~B() //析构函数
{
cout << "Destructor is called. " << data << endl;
}
private:
int data;
};
//函数，参数是一个B类型对象，返回值也是一个B类型的对象
B fun(B b)
{
return b;
}
//测试函数
int _tmain(int argc, _TCHAR* argv[])
{
fun(1);
cout << endl;
B t1 = fun(2);
cout << endl;
B t2;
t2 = fun(3);
return 0;
}
Constructor is called.1 //用1构造参数b
Copy Constructor is called.1 //用b拷贝构造一个临时对象，因为此时没有对象来接受fun的返回值
Destructor is called. 1 //参数b被析构
Destructor is called. 1 //临时对象被析构
Constructor is called.2 //用2构造参数b
Copy Constructor is called.2 //用b拷贝构造t1，此时调用的是拷贝构造函数
Destructor is called. 2 //参数b被析构
Default constructor is called. //调用默认的构造函数构造t2
Constructor is called.3 //用3构造参数b
Copy Constructor is called.3 //用b拷贝构造一个临时对象
Destructor is called. 3 //参数b被析构
The operator "= " is called.3 //调用=操作符初始化t2，此时调用的是赋值操作符
Destructor is called. 3 //临时对象被析构
Destructor is called. 3 //t2被析构
Destructor is called. 2 //t1被析构
请按任意键继续. . .
Breakpoint 2, B::B (this=0x7fffffffde80, i=1) at main.cpp:11
11 B(int i):data(i) //带参数的构造函数
(gdb) s
13 cout << "Constructor is called." << data << endl;
(gdb)
Constructor is called.1
14 }
(gdb)
Breakpoint 7, main () at main.cpp:40
40 fun(b);
(gdb)
Breakpoint 4, B::B (this=0x7fffffffde90, b=...) at main.cpp:17
17 data = b.data; cout << "Copy Constructor is called." << data << endl;
(gdb)
Copy Constructor is called.1
18 }
(gdb)
Breakpoint 5, fun (b=...) at main.cpp:36
36 return b;
(gdb)
Breakpoint 4, B::B (this=0x7fffffffdea0, b=...) at main.cpp:17
17 data = b.data; cout << "Copy Constructor is called." << data << endl;
(gdb)
Copy Constructor is called.1
18 }
(gdb)
fun (b=...) at main.cpp:37
37 }
(gdb)
B::~B (this=0x7fffffffdea0, __in_chrg=<optimized out>) at main.cpp:27
27 cout << "Destructor is called. " << data << endl;
(gdb)
Destructor is called. 1
28 }
(gdb)
B::~B (this=0x7fffffffde90, __in_chrg=<optimized out>) at main.cpp:27
27 cout << "Destructor is called. " << data << endl;
(gdb)
Destructor is called. 1
28 }
(gdb)
main () at main.cpp:41
41 return 0;
(gdb)
(gdb)
Hello World!
(gdb)
B::~B (this=0x7fffffffde80, __in_chrg=<optimized out>) at main.cpp:27
27 cout << "Destructor is called. " << data << endl;
(gdb)
Destructor is called. 1
28 }
(gdb)
main () at main.cpp:44
