[cfe-dev] [LLVMdev] [RFC] Raising LLVM minimum required MSVC version to 2013 for trunk

[DeadMG]

Officially, the latest two major versions- so MSVC 2012 and 2013.

The main issue I'd see here is that all of those features are relatively
untested- for example, in VS 14 CTP3 they had to introduce a new error to
explicitly break all the cases where the compiler silently did totally the
wrong thing. The ones that were included in VS2012 CTP are not quite as
bad. But the reality of using VS2013 is not that all of these features will
suddenly be available to use- there's a lot of compiler issues that would
need to be worked around, including some
silently-generates-totally-the-wrong-code bugs. They can also report
totally incorrect errors- e.g. reporting errors that have nothing to do
with the real error, in totally the wrong location, or both.

Seeing the feature list seems compelling, but MSVC's actual support is
often still below the standard you can find in GCC or Clang, even in
officially supported features. There's a price to be paid not just in terms
of breaking users who are still VS2012-dependent, but also in terms of
debugging VS2013-only bugs.

Personally, I think that it's worth upping the minimum requirement whenever
you're not breaking a substantial portion of your userbase. All I'm saying
is, the experience of many of us using VS2013 is that that feature list is
a little ... optimistic. Upgrading on that basis alone may well yield
undesirable results.

Perhaps it would be better to consider a fork, where the new features are
employed, and then if it doesn't introduce new bugs, it could be merged.
This would also give more time for people to report in with a VS2012
dependency.

On 22 August 2014 17:58, Chris Bieneman <beanz at apple.com> wrote:

>
> On Aug 22, 2014, at 9:53 AM, Daniel Dilts <diltsman at gmail.com> wrote:
>
> On Fri, Aug 22, 2014 at 9:42 AM, Chris Bieneman <beanz at apple.com> wrote:
>
>> Starting a new thread to loop in cfe-dev and lldb-dev. For those not
>> following along there has been a thread on llvm-dev about moving the
>> minimum required Visual Studio version to 2013. The motivating reason is
>> this will allow us to take advantage of a bunch of C++11 features that are
>> not supported by MSVC 2012.
>>
>
> Is there an existing policy on how supported compiler versions are
> selected?
>
>
> There was a discussion last year (
> http://lists.cs.uiuc.edu/pipermail/llvmdev/2013-October/066847.html) WRT
> allowing LLVM to use C++11 features which established a precedent of
> supporting compilers released back for two years, with a special caveat for
> Windows.
>
> -Chris
>
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>
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