Microsoft's C language policy (was: [PATCH 0/1] Add a test balloon for C99)

From: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Date: Nov 30, 2021, 20:43 UTC
Message-ID: <211130.86o861cqnu.gmgdl@evledraar.gmail.com>
In-Reply-To: <20211114212437.1466695-1-sandals@crustytoothpaste.net>

On Sun, Nov 14 2021, brian m. carlson wrote:

[Replying to this tidbit in the v1 CL, which isn't in the V2 one]

Show 24 quoted lines

> Unfortunately, Microsoft for many years refused[1] to support C99 in
> MSVC, and still does not officially do so.  However, they recently added
> support for C11 and C17, which are sufficient for modern programming.
> These require a newer version of MSVC, including an updated SDK.  The
> SDK update is available for download free of charge, and most public CI
> systems have support for both the updated MSVC and the SDK update.
>
> Even for users who would like to target an older version of Windows,
> such as the no longer supported Windows 7, GCC and Clang are available.
> The LLVM suite, including Clang, is available pre-compiled for download
> free of charge.  Using a different compiler is specifically proposed by
> Microsoft staff[1] as a solution for users who wish to build modern
> programs for MSVC versions which do not support modern C.
>
> As such, we can assume that Git can be safely compiled with C99 or C11
> support on all operating systems which receive security support, and
> even some which do not.  Our CI confirms that this series passes all
> tests.  Let's introduce a test balloon which checks for this support and
> fails with an error message if it is absent.
>
> [0] The reader will note that there are people working professionally in
> this industry who were not yet born at the time C99 was ratified.  Thus,
> this occurred quite a long time ago indeed.
> [1] https://herbsutter.com/2012/05/03/reader-qa-what-about-vc-and-c99/

I hadn't seen that blog post before I'd read it when going over your series. I'd assumed that Microsoft was just dragging their feed on C language support, but that post indicates (from what seems to be as official of a source as anyone's going to get) that they're intending to not support C at all, but just some pseudo-C that happens to be a convenient subset of C++.

However that post is from 2012, and you indicate that they've since added (full?) support for C11 and C17.

So is this "policy" of supporting some arbitrary subset of C++ at all current as far as MSVC today goes?

Aside: I just remembered we had a (seemingly abandoned) effort to get git's sources to
compile with a C++ compiler[1], which would be another possible way
forward to using more modern C features that happened to overlap with
C++. Another one would be some sort of coccinelle-powered refactoring or
other source pre-processing...

1. https://lore.kernel.org/git/20180129223728.30569-1-bmwill@google.com/