Add dg-require-wchars to libstdc++ testsuite

[Alexandre Oliva]

On Jan 15, 2021, Jonathan Wakely <jwakely.gcc@gmail.com> wrote:

> On Thu, 14 Jan 2021, 22:22 Alexandre Oliva, <oliva@adacore.com> wrote:
>> ... it is definitely the case that the target currently defines wchar_t,
>> and it even offers wchar.h and a lot of (maybe all?) wcs* functions.
>> This was likely not the case when the patch was first written.
>> 
>> I'll double check whether any of the patch is still needed for current
>> versions.

With the tests I've run since yesterday, I've determined that:

- the wchar-related patches for the libstdc++ testsuite, that I had
  proposed last year, are no longer needed

- your two patchlets did not bring about any regressions to test
  results, not in mainline x86_64-linux-gnu native, not with the trivial
  backports to the gcc-10 tree for x-arm-vxw7r2 that was the focus of my
  immediate attention.

So, I withdraw my submissions of the testsuite patches, and I encourage
you to proceed with the two changes you proposed.

However, for avoidance of any doubt, I'll restate that I cannot vow for
whether they're enough to fix the issues we'd run into back when
wchar/wcs* were not supported in the target system, because now they
are, so the changes do not bring any visible improvements to our results
either.

Anyway, thanks for the feedback!

-- 
Alexandre Oliva, happy hacker  https://FSFLA.org/blogs/lxo/
   Free Software Activist         GNU Toolchain Engineer
        Vim, Vi, Voltei pro Emacs -- GNUlius Caesar