On Nov 20, 2017, at 16:33, Reimar Döffinger <reimar.doeffin...@gmx.de> wrote:
>
> On 20 November 2017 22:19:04 CET, Volodymyr Sapsai <vsap...@apple.com
> <mailto:vsap...@apple.com>> wrote:
>> On Nov 20, 2017, at 11:32, Reimar Döffinger <reimar.doeffin...@gmx.de>
>> wrote:
>>>
>>> On Mon, Nov 20, 2017 at 11:02:13AM -0800, Volodymyr Sapsai wrote:
>>>>> catch (...)
>>>>> {
>>>>> + if (__n > 0)
>>>>> + *__s = char_type();
>>>>> this->__set_badbit_and_consider_rethrow();
>>>>> }
>>>>
>>>> or maybe something else?
>>>
>>> That one (note that the __set_badbit_and_consider_rethrow
>>> will never re-throw in this case).
>>
>> But by #define _LIBCPP_NO_EXCEPTIONS 1 you exclude this block at
>> preprocessing step
>>
>>> #ifndef _LIBCPP_NO_EXCEPTIONS
>>> }
>>> catch (...)
>>> {
>>> + if (__n > 0)
>>> + *__s = char_type();
>>> this->__set_badbit_and_consider_rethrow();
>>> }
>>> #endif // _LIBCPP_NO_EXCEPTIONS
>>
>> And looks like getline_pointer_size_exception.pass.cpp doesn’t execute
>> this code.
>
> Yes, that was complete nonsense, I somehow always read #ifdef where there was
> an #ifndef...
> Not sure then if that 0 termination should be there (and be tested) or better
> to not have it in the exception case at all (I haven't checked if the
> exception is always re-thrown or not, which might be relevant).
> I am a bit unclear about that whole code there that catches exceptions and
> sets the bad bit and how it maps to the specification.
Standard mentions
> Otherwise, if the sentry constructor exits by throwing an exception or if the
> sentry object returns false, when converted to a value of type bool, the
> function returns without attempting to obtain any input. In either case the
> number of extracted characters is set to 0; unformatted input functions
> taking a character array of non-zero size as an argument shall also store a
> null character (using charT()) in the first location of the array.
My understanding is that if sentry constructor throws an exception we need to
null-terminate a character array. Null-termination isn’t specified explicitly
for exceptions thrown in other cases but I think it would be more cumbersome to
perform null-termination only for sentry exceptions and not for others.
Regarding the safety, we control __s, don’t pass it anywhere, it never points
beyond __n - I think null-termination should be safe. Also libstdc++ does
null-termination when exceptions are thrown.
As for rethrowing exception, looks like exceptions flag std::istream::eofbit
causes exception to be thrown and std::istream::badbit to be rethrown according
to
> If (exceptions()&badbit) != 0 then the exception is rethrown.
And looks like libstdc++ rethrows exception even if badbit is not set.
If you feel comfortable, I can finish exception tests myself and commit the
patch. How does it sound?
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