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

[Jonathan Wakely <jwakely dot gcc at gmail dot com>]

On 26 October 2016 at 17:46, Edward Diener wrote:
> On 10/26/2016 10:57 AM, Jonathan Wakely wrote:
>>
>> On 26 October 2016 at 14:42, Edward Diener wrote:
>>>
>>> I am missing the syntactical difference between the two. There is
>>> 'std::ios_base::failure' and how do you specify the other one ? Your
>>> notation of 'std::ios_base::[abi:__cxx11]failure' I do not understand.
>>>
>>
>> It comes from the abi_tag attribute documented at
>> https://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Attributes.html
>>
>> namespace std {
>>   struct ios_base {
>>     struct __attribute__((abi__tag__("cxx11"))) failure { };
>>   };
>> }
>>
>> I got the demangled name slightly wrong, the attribute goes at the end:
>>
>> #include <iostream>
>> int main()
>> {
>>   throw std::ios_base::failure("");
>> }
>> terminate called after throwing an instance of
>> 'std::ios_base::failure[abi:cxx11]'
>>   what():  : iostream error
>> Aborted (core dumped)
>
>
> I am syntactically catching 'std::ios::failure'. Are you saying that the
> exception being thrown in my OP is actually
> 'std::ios_base::failure[abi:cxx11]' ? I am still a bit confused when you
> said in a previous reply:
>
>
> "You're trying to catch the new one, but the library throws the old
> one."

I meant exactly that. You're trying to catch the new type, which has a
std::system_error base class and is decorated with
__attribute__((__abi_tag__("cxx11"))), but the library throws the old
type, which is not decorated with the attribute.