c++从入门到精通——异常变量生命周期

不念不忘少年蓝@ 2023-02-16 00:46 1阅读 0赞

# 异常变量生命周期 #

## 测试1(返回对象会多拷贝一份浪费内存) ##

#define _CRT_SECURE_NO_WARNINGS
    #include<iostream>
    using namespace std;
    
    class MyException
    { 
    public:
    	MyException()
    	{ 
    		cout << "MyException的默认构造" << endl;
    	}
    	MyException(const MyException & e)
    	{ 
    		cout << "MyException的拷贝构造" << endl;
    	}
    	
    	~MyException()
    	{ 
    		cout << "MyException的析构调用" << endl;
    	}
    };
    
    void doWork()
    { 
    	throw  MyException();
    }
    
    void test01()
    { 
    	try
    	{ 
    		doWork();
    	}
    	catch (MyException e)//普通写法会多开销一份数据
    	{ 
    		cout << "捕获异常" << endl;
    	}
    
    }
    
    
    int main(){ 
    
    
    	test01();
    
    	system("pause");
    	return EXIT_SUCCESS;
    }

运行

MyException的默认构造
    MyException的拷贝构造
    捕获异常
    MyException的析构调用
    MyException的析构调用

## 测试2(推荐返回引用) ##

把`catch (MyException e)`改为`catch (MyException &e)`，改成返回引用。

#define _CRT_SECURE_NO_WARNINGS
    #include<iostream>
    using namespace std;
    
    class MyException
    { 
    public:
    	MyException()
    	{ 
    		cout << "MyException的默认构造" << endl;
    	}
    	MyException(const MyException & e)
    	{ 
    		cout << "MyException的拷贝构造" << endl;
    	}
    
    	~MyException()
    	{ 
    		cout << "MyException的析构调用" << endl;
    	}
    };
    
    void doWork()
    { 
    	throw  MyException();
    }
    
    void test01()
    { 
    	try
    	{ 
    		doWork();
    	}
    	catch (MyException &e)
    	{ 
    		cout << "捕获异常" << endl;
    	}
    
    }
    
    
    int main(){ 
    
    
    	test01();
    
    	system("pause");
    	return EXIT_SUCCESS;
    }

运行

MyException的默认构造
    捕获异常
    MyException的析构调用

## 测试3(返回指针不推荐) ##

#define _CRT_SECURE_NO_WARNINGS
    #include<iostream>
    using namespace std;
    
    class MyException
    { 
    public:
    	MyException()
    	{ 
    		cout << "MyException的默认构造" << endl;
    	}
    	MyException(const MyException & e)
    	{ 
    		cout << "MyException的拷贝构造" << endl;
    	}
    
    	~MyException()
    	{ 
    		cout << "MyException的析构调用" << endl;
    	}
    };
    
    void doWork()
    { 
    	throw  &MyException();
    }
    
    void test01()
    { 
    	try
    	{ 
    		doWork();
    	}
    	catch (MyException *e)
    	{ 
    		cout << "捕获异常" << endl;
    		
    		delete e;//靠自觉 释放对象
    	}
    
    }
    
    
    int main(){ 
    
    	test01();
    
    	return 0;
    }