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Subject: Re: Wide characters with multiple c-chars
From: Corentin (corentin.jabot_at_[hidden])
Date: 2020-07-02 02:31:31


On Thu, 2 Jul 2020 at 09:09, Corentin <corentin.jabot_at_[hidden]> wrote:

> Hello,
> As part of https://wg21.link/p2178r0,
>
> I would like to make *wide* characters litteral with multiple c-char (ie:
> L'abc') ill-formed
> https://compiler-explorer.com/z/MHExrk
>

I forgot to mention that it's extra fun with combining characters
https://compiler-explorer.com/z/ndyyAD (the value of b is equivalent to
L'e\u0301')

>
> All compilers but MSVC emit a warning by default, some
> implementations pick the first c-char, others pick the last.
> There is no use (no occurrence in any of the packages in vcpkg) or usage
> for this feature.
>
> So why do this?
> - Someone unfamiliar with C++ might do auto str = L'abc' instead of L"abc"
> - Things that are not useful should not linger for 40 more years in the
> standard; Tom and I talked too much about how to word this "feature" as
> part of P2029, so it's not free.
> - It's part of a wider "Bogus conversions in phase 5" should be ill-formed
> rather than doing their best to compile *something*
>
> Please note that I am not proposing to make (narrow) multi character
> literals ill-formed or deprecated at this point, there are some uses, and
> these uses are intended.
>
> I would really like your opinion so we can propose that change to EWG and
> make the change without taking too much of anyone's time (the process
> really isn't tuned for very small changes, which is why that is part of a
> larger paper)
>
> Thanks a lot,
> Corentin
>
>
>
>



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