Re: type of decimal constants in msvc

From	Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups	comp.lang.c
Subject	Re: type of decimal constants in msvc
Date	2025-09-02 13:46 -0700
Organization	None to speak of
Message-ID	<87jz2gbn19.fsf@example.invalid> (permalink)
References	<1097ivh$ntii$1@dont-email.me>

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Thiago Adams <thiago.adams@gmail.com> writes:
> The type used by MSVC compiler seems not follow the C standard.
>
> I choose the number 2147483648 that is the next number after max signed i32.
>
> I was expecting "signed long long" (the next signed type) but MSVC
> instead uses unsigned long (that is 32 bits)
>
>
> #define is_type(T, E) _Generic(E, T : 1 , default:0 )
>
> static_assert(is_type(unsigned long, 2147483648));
>
> int main(){}
>
> https://godbolt.org/z/EqKWroecj
>
>
> The the standard says
> "The type of an integer constant is the first of the
> corresponding list in which its value can be represented."
>
> No suffix: The potential types, in order, are int, long int, and long
> long int.

Yes, that appears to be a bug.

I tried an example myself with Visual Studio 2022.  By default, it gives
2147483648 a type of unsigned long.

The default configuration is "/std:c17".  I thought it might be an
"extension" that I can disable with "/Za", but astonishingly that
produces a fatal error:

error D8016: '/Za' and '/std:c17' command-line options are incompatible

*Maybe* there's some combination of options that will persuade it to
behave correctly.

> So I think when "cloning" MSVC I need to not follow the standard.

I suppose, but it depends on why you want to clone MSVC and whether you
need to replicate its bugs.

I don't know whether this bug has been reported to Microsoft.  If not,
it should be.

> In GCC the type is long (that is 64 bits)
>
> https://godbolt.org/z/eTKE19r8K

On targets with 32-bit long, it should be long long.

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
void Void(void) { Void(); } /* The recursive call of the void */

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type of decimal constants in msvc Thiago Adams <thiago.adams@gmail.com> - 2025-09-02 17:10 -0300
  Re: type of decimal constants in msvc Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-09-02 13:46 -0700
    Re: type of decimal constants in msvc Thiago Adams <thiago.adams@gmail.com> - 2025-09-02 20:39 -0300
  Re: type of decimal constants in msvc Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-09-03 06:42 +0000
    Re: type of decimal constants in msvc BGB <cr88192@gmail.com> - 2025-09-03 10:59 -0500
    Re: type of decimal constants in msvc Michael S <already5chosen@yahoo.com> - 2025-09-04 15:21 +0300
  Re: type of decimal constants in msvc Thiago Adams <thiago.adams@gmail.com> - 2025-09-03 16:04 -0300

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