Add dg-require-wchars to libstdc++ testsuite

[Jonathan Wakely]

On 13/01/21 14:29 -0300, Alexandre Oliva wrote:
>On Dec 28, 2020, François Dumont <frs.dumont@gmail.com> wrote:
>
>> On 22/12/20 10:12 pm, Alexandre Oliva wrote:
>>> Some tests uses structures from the libstdc++ that are present only if
>>> the target has a wchar.h header.  However, those tests do not check
>>> that the target supports those constructs before executing the tests.
>
>> Looks like those tests should be in some sub-folder containing
>> 'wchar_t' to be considered as UNSUP.
>
>> Maybe Jonathan will prefer them to be moved even if your approach
>> seems more convenient to me.
>
>I'd be glad to make such changes, but I'd appreciate stronger guidance
>as to the preferences and the way to go before doing so.  Jonathan,
>would you please share your wisdom WRT this patch and the other
>wchar_t-related libstdc++ testsuite one?
>
>https://gcc.gnu.org/pipermail/gcc-patches/2020-December/562435.html
>https://gcc.gnu.org/pipermail/gcc-patches/2020-December/562438.html

I'll look at them today.

>>> The function dg-require-wchars checks that "_GLIBCXX_USE_WCHAR_T" is
>>> defined by the configure of the libstdc++.  If it is not the case, the
>>> test is not executed.
>
>> This check_v3_target_wchars looks like a good candidate to leverage
>> on: v3_check_preprocessor_condition.
>
>Nice!, thanks for the tip, I was not aware of this proc.

It's only been there a few weeks.