自己编译时候的一个警告by earlier handler for ‘std::exception’

看自己编写的下面一段代码

#include <string>
#include <iostream>
#include <stdexcept>
#include <exception>
#include <new>
//#include <type_info>
using namespace std;
int main()
{
int a = 0;
try{
	if(a == 0)
		throw exception();
	if(a == 1)
		throw bad_alloc();

	if(a == 2)
		throw bad_cast();
}
catch (exception e){ cout <<  e.what() << endl;}
catch (bad_alloc e){ cout << e.what() << endl;}
catch (bad_cast e){cout << e.what()  << endl;}

	return 9;
}

g++编译器，编译时候会提示警告：

3.cc:21:1: warning: exception of type ‘std::bad_alloc’ will be caught
 catch (bad_alloc e){ cout << e.what() << endl;}
 ^~~~~
3.cc:20:1: warning:    by earlier handler for ‘std::exception’
 catch (exception e){ cout <<  e.what() << endl;}

自己稍微查了下，发现catch语句块必须得安排下顺序，不能随意乱安排。所以自己改了下：

把 catch (exception e){}放在最后。在c++primer书上也说过，越是具体的异常类型处理，越是得放在前面。越是通用的异常，越该放后面。