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

[Simon Pilgrim via llvm-dev]

Thanks for the responses, it looks like making VS2019 the minimum 
supported version sooner rather than later will help a number of cases.

I'll create a patch this weekend, for review next week when more people 
are back after the USA holiday.

Simon.

On 25/11/2021 12:57, James Henderson via llvm-dev wrote:
> 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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