[Python-Dev] C99

[Guido van Rossum]

I want it to list specific versions that are known to be good right
now, so we can point fingers appropriately when a regression happens.
If you have to ask Steve what version he used, ask!

On Fri, Aug 5, 2016 at 3:15 PM, Brett Cannon <brett at python.org> wrote:
>
>
> On Fri, 5 Aug 2016 at 15:07 Guido van Rossum <gvanrossum at gmail.com> wrote:
>>
>> That sounds fine to me, but we need to list specific compiler versions.
>
>
> Would you want this to be static (e.g. MSVC 2016 until we choose to update
> to support C11), or would you want it to vary based on what's available when
> the current/last Python is/was released (e.g. whatever version of MSVC Steve
> uses to build the binaries for 3.5 or 3.6 in our current case)?
>
>>
>>
>> On Fri, Aug 5, 2016 at 2:04 PM, Brett Cannon <brett at python.org> wrote:
>> > Where did we finally land on this discussion? Do we want to update PEP 7
>> > to
>> > say that starting in 3.6 we may use C99 features common to all supported
>> > compilers and list what those compilers are (i.e. gcc, clang, and MSVC)?
>> >
>> > On Wed, 8 Jun 2016 at 01:28 Victor Stinner <victor.stinner at gmail.com>
>> > wrote:
>> >>
>> >> I guess that as usual, we should use the "common denominator" of all
>> >> compilers supported by CPython. For example, if MSVC doesn't support a
>> >> feature, we should not use it in CPython.
>> >>
>> >> In practice, it's easy to check if a feature is supported or not: we
>> >> have buildbots building Python at each commit. It was very common to
>> >> get a compilation error only on MSVC when a variable was defined in
>> >> the middle of a function. We are now using
>> >> -Werror=declaration-after-statement with GCC because of MSVC!
>> >>
>> >> Maybe GCC has an option to ask for the subset of the C99 standard
>> >> compatible with MSVC? Something like "-std=c99 -pedantic"?
>> >>
>> >> Note: I tried -pedantic, GCC emits a lot of warnings on code which
>> >> looks valid and/or is protected with #ifdef for features specific to
>> >> GCC like computed goto.
>> >>
>> >> Victor
>> >>
>> >> 2016-06-07 21:45 GMT+02:00 Guido van Rossum <gvanrossum at gmail.com>:
>> >> > We should definitely keep supporting MSVC.
>> >> >
>> >> > --Guido (mobile)
>> >> >
>> >> > On Jun 7, 2016 12:39 PM, "Sturla Molden" <sturla.molden at gmail.com>
>> >> > wrote:
>> >> >>
>> >> >> Victor Stinner <victor.stinner at gmail.com> wrote:
>> >> >>
>> >> >> > Is it worth to support a compiler that in 2016 doesn't support the
>> >> >> > C
>> >> >> > standard released in 1999, 17 years ago?
>> >> >>
>> >> >> MSVC only supports C99 when its needed for C++11 or some MS
>> >> >> extension
>> >> >> to
>> >> >> C.
>> >> >>
>> >> >> Is it worth supporting MSVC? If not, we have Intel C, Clang and
>> >> >> Cygwin
>> >> >> GCC
>> >> >> are the viable options we have on Windows (and perhaps Embarcadero,
>> >> >> but
>> >> >> I
>> >> >> haven't used C++ builder for a very long time). Even MinGW does not
>> >> >> fully
>> >> >> support C99, because it depends on Microsoft's CRT. If we think MSVC
>> >> >> and
>> >> >> MinGW are worth supporting, we cannot just use C99 indiscriminantly.
>> >> >>
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>> >> >>
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>> >> >
>> >> >
>> >> > _______________________________________________
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>> >> >
>> >> >
>> >> > https://mail.python.org/mailman/options/python-dev/victor.stinner%40gmail.com
>> >> >
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>>
>>
>>
>> --
>> --Guido van Rossum (python.org/~guido)



-- 
--Guido van Rossum (python.org/~guido)