C++异常处理（一）----基本语法

• 实验环境 win7 下的vs2017，基本原则：throw抛出的数据类型，和cathc语句的数据类型要一致
• 异常的引发和异常的处理可以分布在不同函数中，所以c++的异常是跨栈的

• 异常是由“地地道道“的错误所引发

#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include<string.h>
using namespace std;

void testerror(int x,int y)
{

    if (y==0)
    {
        throw x;
    }
    cout << "计算结果："<<x/y<< endl;
}

void main()
{
    try
    {
        testerror(100,0);
    }
    catch (int x)
    {
        cout  << x << "不能被0整除" << endl;
    }
    catch (...)
    {
        cout << "无言的结局" << endl;
    }
    system("pause");
}

• 下面的例子揭示了throw语句的强大，无论多少层都会抛出错误

void testerror(int x,int y)
{

    if (y==0)
    {
        throw x;
    }
    cout << "计算结果："<<x/y<< endl;
}

void awrap()
{
    testerror(100, 0);
}

void main()
{
    //
    try
    {
        awrap();
    }
    catch (int x)
    {
        cout  << x << "不能被0整除" << endl;
    }
    catch (...)
    {
        cout << "无言的结局" << endl;
    }
    system("pause");
}

输出结果：

•  一个字符串比较的例子

void testerror(char * name)
{
    cout << "his name is " << name << endl;
    if (strcmp(name,"雨化田")==0)
    {
        throw name;
    }
    cout << "原来是：" << name << "！快快进来享用广式炒面" << endl;
}

int main()
{
    //
    char name[] = "雨化田";
    char *hisname = name;
    try
    {
        testerror(hisname);
    }
    catch (char *name)
    {
        cout << "妈爷子诶~这不是：" << name << endl;
    }
    catch (...)
    {
        cout << "无言的结局" << endl;
    }
    system("pause");
    return 0;
}

输出结果：

• 栈解旋(unwinding)：当异常抛出为栈对象时，异常处理可以达到析构异常对象的效果

#include<iostream>
using namespace std;

class mycoach
{
public:
    friend void freeobj(mycoach &t);
    mycoach(char *myname, int age,int months)
    {
        this->myname = myname;
        this->age = age;
        this->months = months;
    }
    ~mycoach()
    {
        cout << "free of space" << endl;
    }
private:
    char *myname;
    int age;
    int months;
};

void freeobj(mycoach &t)
{
    if (t.age < 16)
    {
        cout <<"精神可嘉~但还是年龄太小" <<endl;
        throw t.age;
    }
    if (t.months <= 12)
    {
        cout << "精神可嘉~再练一段时间，加油" << endl;
        throw t.months;
    }
    //throw t;
}


void main() 
{
    char name[] = "章小军";
    char *hisname = name;
    mycoach mt(hisname,16,1);
    try
    {
        freeobj(mt);
    }
    catch (int a)
    {
        cout << "少于规定训练时间(12个月)实际:"<<a <<"个月"<< endl;
    }
    catch (...)
    {
        cout << "无言的结局" << endl;
    }
    system("pause");
    //return 0;
}

输出结果：

 其中，按下任意键之后，执行了析构函数也就是所谓的”栈解旋“