[PATCH] libstdc++: Fix format call and test formatting with empty specs for durations.

[Daniel Krügler]

Am Mi., 4. Juni 2025 um 12:57 Uhr schrieb Tomasz Kaminski <
tkaminsk@redhat.com>:

>
>
> On Wed, Jun 4, 2025 at 12:43 PM Daniel Krügler <daniel.kruegler@gmail.com>
> wrote:
>
>> Am Mi., 4. Juni 2025 um 11:27 Uhr schrieb Tomasz Kamiński <
>> tkaminsk@redhat.com>:
>>
>>> [...]
>>> +
>>> +template<typename Ret, typename Other>
>>> +  requires std::is_integral_v<Other>
>>> +struct std::common_type<Rep<Ret>, Other>
>>> +{
>>> +  using type = Rep<Ret>;
>>> +};
>>> +
>>> +template<typename Ret, typename Other>
>>> +  requires std::is_integral_v<Other>
>>> +struct std::common_type<Other, Rep<Ret>>
>>> +  : std::common_type<Rep<Ret>, Other>
>>> +{ };
>>>
>>
>> Why is this second specialization needed? It seems to me
>> that [meta.trans.other] p5 says that it is already provided by the library
>> implementation of  std::common_type.
>>
> My reading of the paragraph is different. It says that if one is
> specialized, we also need to specialize the other:
> > Moreover, common_type_t<T1, T2> shall denote the same type, if any, as
> does common_type_t<T2, T1>.
> <https://eel.is/c++draft/meta.trans.other#5.sentence-4>
> > No diagnostic is required for a violation of this Note's rules.
> <https://eel.is/c++draft/meta.trans.other#5.sentence-5>
> "shall" are requirements on the users.
>

Yes you are right, sorry for the noise.

- Daniel
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