Re: [PATCH] [vxworks] make wint_t and wchar_t the same distinct type

[Jason Merrill <jason@redhat.com>]

On 2/22/23 10:23, Alexandre Oliva wrote:
> Hello, Jason,
> 
> On Feb 17, 2023, Jason Merrill <jason@redhat.com> wrote:
> 
>> On 2/17/23 23:04, Alexandre Oliva wrote:
>>>
>>> We used to define WINT_TYPE to WCHAR_TYPE, so that both wint_t and
>>> wchar_t mapped to the same underlying type, but this caused a glitch
>>> in Wstringop-overflow-6.C: on vxworks, wint_t is typedef'ed to
>>> wchar_t
> 
>> And fixing that isn't an option?
> 
> Erhm, why do you say "fixing"?  That implies it's broken, but I don't
> see anything in the C++ standards, or in the relevant bits that it
> imports from the C standards, that rules out using wint_t = wchar_t in
> C++.  wint_t is imported from the C standard as an integral type that
> meets certain requirements, and AFAICT in C++ wchar_t is an integral
> type that meets those requirements.  Am I missing something?
> 
> 
> Now, could it be changed so that wint_t is wchar_t's underlying type
> rather than wchar_t?  If the equivalence is a compliance error, we could
> file a bug report with WRS and request them to fix it, but modifying
> their system headers would require a copyright license they don't grant,
> so we avoid doing that.  I imagine that breaking this equivalence would
> have ABI implications, and even break legitimate (though unportable)
> programs because of overload, specializations and whatnot, so there
> would have to be very strong reasons to support a request for such a
> change.
> 
>> Do the integer builtins work properly if we force them to use wchar_t
>> instead of an integer type?
> 
> I haven't observed any regressions, I don't see any builtin functions
> with wint in their signature that we even expand as builtins, and my
> imagination is failing me on why an integral type such as wchar_t would
> fail for wint_t, where other integral types, including wchar_t's
> underlying type, would work.  Did you have any specific risks in mind
> about what could go wrong?

Sorry, I think I was mostly confusing myself about how distinct wchar_t 
really is.

The patch is OK.

Jason