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

[Edward Diener]

On 10/26/2016 7:51 AM, Jonathan Wakely wrote:
> On 26 October 2016 at 12:48, Jonathan Wakely wrote:
>> On 26 October 2016 at 12:45, Edward Diener wrote:
>>> If I have code asuch as:
>>>
>>> std::stringstream ss;
>>> ss.exceptions(std::ios_base::failbit | std::ios_base::badbit);
>>> char c;
>>> ss >> c;
>>>
>>> I would except an exception of std::ios_base::failure to be thrown yet gcc
>>> 6.2 is throwing some other exception. Is there a reason for this ?
>>
>> There are two versions of std::ios::failure, one using the old ABI
>> (called std::ios_base::failure) and one using the new ABI (called
>> std::ios_base::[abi:__cxx11]failure).
>>
>> You're trying to catch the new one, but the library throws the old
>> one. I'm probably going to change the library to throw the new one for
>> GCC 7.
>
>
> I forgot to say, the reason for the two versions is that C++11
> required an ABI break for that type, adding a new std::system_error
> base class, with extra data members. That base class wasn't present in
> C++98 (because the type didn't exist) and so we've been shipping a
> library for years that throws the old type.
>
> 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 ?