[llvm-dev] [RFC] Raise the minimum Visual Studio version to VS2019

[James Henderson via llvm-dev]

I'm also personally in favour of this - a couple of months ago I ran into a
bug with the VS2017 compiler that isn't present in the VS2019 one, that was
preventing me using std::enable_if in a way I'd have liked to. Being able
to retire VS2017 support would simplify a few things for me.

James

On Thu, 25 Nov 2021 at 12:30, Jan Svoboda via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> I'm in support of this proposal.
>
> I hit an unexpected preprocessor behavior in VS2017, forcing me to revert
> a patch that removed some repetitive code (D95532). The flag that fixes the
> issue (`/experimental:preprocessor`) is only present in Visual Studio 2017
> version 15.8 and later. Raising the minimum supported version to VS2019
> would allow us to enable `/Zc:preprocessor` and re-land the patch.
>
> Cheers,
> Jan
>
> > On Nov 23, 2021, at 5:47 PM, Michael Kruse via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
> >
> > By our policy to support the last 2 major versions of VS, this is the
> > right thing to do. Removing support for old compiler versions lessens
> > the maintenance burden, e.g. when committing a change that happens to
> > run a bug/missing feature of VS2017.
> >
> > If I am not mistaken, the value of the latest VS2019 is 1929, not 1927
> [1].
> >
> > Michael
> >
> > [1]
> https://docs.microsoft.com/en-us/cpp/preprocessor/predefined-macros?view=msvc-170
> >
> > Am Di., 23. Nov. 2021 um 05:56 Uhr schrieb Simon Pilgrim via llvm-dev
> > <llvm-dev at lists.llvm.org>:
> >>
> >> Now that VS2022 is on general release, LLVM is expected to build on
> >> VS2017, VS2019 and VS2022.
> >>
> >> What are people's thoughts on raising the minimum supported version to
> >> latest VS2019 (_MSC_VER = 1927)? Customarily, we've only specifically
> >> supported the latest 2 versions of Visual Studio, with older versions
> >> being "allowed" (at your own risk) via the LLVM_FORCE_USE_OLD_TOOLCHAIN
> >> cmake flag.
> >>
> >> I'm thinking we should either make the switch now, in plenty of time
> >> before the next release of LLVM, or we postpone it until shortly after
> >> the release branch is created (which I assume will be early 2022).
> >>
> >> For the record, I haven't so far noticed any issues with supporting
> >> VS2017, VS2019 and VS2022 builds, so at this time I don't consider this
> >> very urgent, just a general maintenance task - although somebody out
> >> there may know of specific fixes in VS2019+ that could simplify LLVM
> >> handling for MSVC etc.
> >>
> >> Cheers, Simon.
> >>
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