《c++大学教程》读书笔记 （第13章 异常处理）

      这一章所介绍的似乎简略了一些。当然，我也不知该怎么样写才算说得清楚，毕竟我才初学C++，只是看得我不太爽，有些地方不明白。

这章总的有两点不足：1.说得不够深入。2.例子不够精辟。

      其中有个例子（因为内存比较大，做了点修改）我在上机的时候就发生错误，abort了。一开始就new失败。（VC6.0)

#include <iostream>
#include <new>
using namespace std;


void customNewHandler()
{
    cerr<<“customNewHandler was called “    abort();
}

int main()
{
    double *ptr[9999    set_new_handler(customNewHandler);

    

        for(int i=0<9999++)
     {
            ptr[i]=new double[5000000
            cout<<“Allocated 5000000 double s in ptr[“<<i<<“]n“        }
    



    return 0
}

#include <iostream>
#include <new>
using namespace std;


int main()
{
    double *ptr[9999

    try
    {
        for(int i=0<9999++)
        {
            ptr[i]=new double[5000000
            cout<<“Allocated 5000000 double s in ptr[“<<i<<“]n“        }
    }
    catch(bad_alloc &ex)
    {
        cout<<“Exception occurred:“
            <<ex.what()<<endl;
    }


    return 0
}

       在VC6.0编译运行时，不知说它聪明还是傻，竟然分配到9998个数组，用了系统虚拟内存。所以看不到抛出异常的结果。

而在gcc和VC7上都得到满意答案。gcc结果如下：

Allocated 5000000 double s in ptr[0]
Allocated 5000000 double s in ptr[1]
Allocated 5000000 double s in ptr[2]
Allocated 5000000 double s in ptr[3]
Allocated 5000000 double s in ptr[4]
Allocated 5000000 double s in ptr[5]
Allocated 5000000 double s in ptr[6]
Allocated 5000000 double s in ptr[7]
Allocated 5000000 double s in ptr[8]
Allocated 5000000 double s in ptr[9]
Allocated 5000000 double s in ptr[10]
Allocated 5000000 double s in ptr[11]
Allocated 5000000 double s in ptr[12]
Allocated 5000000 double s in ptr[13]
Allocated 5000000 double s in ptr[14]
Allocated 5000000 double s in ptr[15]
Allocated 5000000 double s in ptr[16]
Allocated 5000000 double s in ptr[17]
Allocated 5000000 double s in ptr[18]
Allocated 5000000 double s in ptr[19]
Allocated 5000000 double s in ptr[20]
Allocated 5000000 double s in ptr[21]
Allocated 5000000 double s in ptr[22]
Allocated 5000000 double s in ptr[23]
Allocated 5000000 double s in ptr[24]
Allocated 5000000 double s in ptr[25]
Allocated 5000000 double s in ptr[26]
Allocated 5000000 double s in ptr[27]
Exception occurred:St9bad_alloc

  VC7结果如下：
Allocated 5000000 double s in ptr[0]
Allocated 5000000 double s in ptr[1]
Allocated 5000000 double s in ptr[2]
Allocated 5000000 double s in ptr[3]
Allocated 5000000 double s in ptr[4]
Allocated 5000000 double s in ptr[5]
Allocated 5000000 double s in ptr[6]
Allocated 5000000 double s in ptr[7]
Allocated 5000000 double s in ptr[8]
Allocated 5000000 double s in ptr[9]
Allocated 5000000 double s in ptr[10]
Allocated 5000000 double s in ptr[11]
Allocated 5000000 double s in ptr[12]
Allocated 5000000 double s in ptr[13]
Allocated 5000000 double s in ptr[14]
Allocated 5000000 double s in ptr[15]
Allocated 5000000 double s in ptr[16]
Allocated 5000000 double s in ptr[17]
Allocated 5000000 double s in ptr[18]
Allocated 5000000 double s in ptr[19]
Allocated 5000000 double s in ptr[20]
Allocated 5000000 double s in ptr[21]
Allocated 5000000 double s in ptr[22]
Allocated 5000000 double s in ptr[23]
Allocated 5000000 double s in ptr[24]
Allocated 5000000 double s in ptr[25]
Allocated 5000000 double s in ptr[26]
Allocated 5000000 double s in ptr[27]
Exception occurred:bad allocation

     一些基本概念
异常可以处理的情况：
1。内存不足以满足new请求
2。数组下标越界。
3。运算溢出
4。除数为0
5。无效函数参数

不可以处理情况：
1。磁盘I/O完成
2。网络消息送达
3。鼠标单击
4。等等。。。

C++异常处理关键字： try、throw、catch

简单处理例子：除数为0