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

[Jonathan Wakely]

On 27 October 2016 at 15:34, Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
> On 27 October 2016 at 15:30, Edward Diener
> <eldlistmailingz@tropicsoft.com> wrote:
>> On 10/27/2016 10:00 AM, Jonathan Wakely wrote:
>>>
>>> On 27 October 2016 at 14:52, Edward Diener wrote:
>>>>
>>>> It sounds like you are also saying that there is no way to catch the old
>>>> type, even if I wanted to, since the header file declaration has the
>>>> decorated attribute.
>>>
>>>
>>> No, the attribute is only present conditionally, see
>>> https://gcc.gnu.org/onlinedocs/libstdc++/manual/using_dual_abi.html
>>>
>>> If you compile with _GLIBCXX_USE_CXX11_ABI defined to zero then you
>>> get the declaration of the old type (and the old COW std::string, and
>>> the old std::list with O(n) size()).
>>>
>>
>> Thanks ! IMO clearly you should be throwing the std::ios_base::failure which
>> corresponds to the _GLIBCXX_USE_CXX11_ABI macro setting being used.
>
> The exception is thrown from code inside libstdc++.so, which is
> already compiled and can't be affected by a macro defined when you
> #include <iostream>.
>
> We could maybe set a thread-local variable every time an iostream
> operation is performed, based on the macro value, and have the library
> inspect the thread-local to decide which type to throw, but that would
> be ugly, and still not always do the right thing.
>
>
>> That gcc
>> is throwing the the old type even when _GLIBCXX_USE_CXX11_ABI is defined as
>> 1 cannot be right. But I think that is what you already said.
>
> No, I said I'm going to change it to always throw the new type. It
> will won't depend on the macro.

Sorry, that was meant to say it *still* won't depend on the macro.