相关疑难解决方法(0)

试验I/OI得到一个异常,不应该抛出任何异常:

#include <iostream>
#include <fstream>

int main()
{
    std::ifstream f("/tmp");
    std::cout << "Exception Flags: " << f.exceptions() << std::endl;
    if(f >> std::ws) std::cout << "This will not succeed" << std::endl;
    else std::cout << "Ok - it fails" << std::endl;
    return 0;
}

但输出是:

Exception Flags: 0
terminate called after throwing an instance of 'std::ios_base::failure'
  what():  basic_filebuf::underflow error reading the file
Aborted

g ++(Ubuntu/Linaro 4.7.2-2ubuntu1)4.7.2

编辑

测试应该毫无例外地失败:

从27.5.5.4 basic_ios标志函数

void clear(iostate state = goodbit);

4后置条件:如果rdbuf()!= 0则state == rdstate(); 否则rdstate()==(state | ios_base …