异常执行顺序(exception specification)
2008-04-09 06:48 ubunoon 阅读(369) 评论(0) 编辑 收藏 举报之前都没有好好练习过异常,也没有深入了解过,最近在看Thinking In C++中,它的第一章就讲述了大量的异常代码,本以为很简单,然而在机器上编译调试了一番,才发现并不是那么一回事。在执行下面的异常程序中,发现很有些特色(可能老手早就熟悉了),记录下来, 以便将来查看!程序源代码为:
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整个程序结构非常简单,set_unexpected函数是exception头文件中提供的标准函数,用来设置抛出的异常没有列在异常规格说明(exception specification)的异常集中调用的unexpected函数(默认)
f 函数申明了异常规格说明集合,但调用了版本2的g 函数,而该函数抛出的异常却不在f 函数的异常规格说明集合中,因此将默认调用unexpected函数,此处将调用my_unexpected函数。
在VC中调试运行该函数,抛出出错对话框:
之后调试该程序,才惊奇的发现该程序运行顺序为
首先执行for语句,然后执行try块中的f 函数调用,之后抛出Up异常,跳转到catch(Up)语句处执行,输出Up caught后,跳转到return 0语句,之后再执行for语句,再一次循环,抛出Fit异常,return 0之后再运行for语句,抛出Debug Error 对话框!
原来异常程序的执行是如此的巧妙!
正如文中所说:把try块嵌入在for,while,do或if块中,并且触发异常来试图解决问题;然后重新测试try块中的代码!也就是说,即使其中一个执行过程抛出了异常,for,while,do或if等都能够继续执行下去,只针对其中一个过程产生影响,对全局影响并不是很大。
该程序在cygwin中可以被正确编译运行!说明了VC对标准C++的支持不是很好!
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