Re: Throwing std::ios_base::failure on formatted input with gcc 6.2

[Edward Diener <eldlistmailingz at tropicsoft dot com>]

On 10/27/2016 6:35 AM, Jonathan Wakely wrote:
> On 27 October 2016 at 04:44, Edward Diener wrote:
> > On 10/26/2016 7:51 AM, Jonathan Wakely wrote:
> > > They both have a base class of std::runtime_error so you can still
> > > catch it as that, or std::exception.
> >
> > The program:
> >
> > #include <iostream>
> > #include <sstream>
> > int main()
> >     {
> >     std::stringstream ss;
> >     ss.exceptions(std::ios_base::failbit | std::ios_base::badbit);
> >     char c;
> >
> >     try
> >         {
> >         ss >> c;
> >         std::cout << "Exception not thrown.";
> >         }
> >     catch (std::runtime_error &)
> >         {
> >         std::cout << "Exception std::runtime_error thrown.";
> >         }
> >     catch (...)
> >         {
> >         std::cout << "Unknown exception thrown.";
> >         }
> >     }
> >
> > when built with gcc-6.2 outputs:
> >
> > 'Unknown exception thrown.'
> >
> > According to what you have written above I would expect the output to be
> >
> > "Exception std::runtime_error thrown."
> >
> > What am I missing here ?
>
> That I was wrong to say both types have a std::runtime_error base.
> C++98 says std::ios_base::failure derives directly from
> std::exception.

Even when I add -std=c++11 to the command line, the same result occurs.

I can even add:

    catch (std::ios_base::failure &)
        {
        std::cout << "Exception std::ios_base::failure thrown.";
        }

before:

    catch (std::runtime_error &)
        {
        std::cout << "Exception std::runtime_error thrown.";
        }

in my example above, and compile with -std=c++11, and the output is 
still "Unknown exception thrown."