[cfe-dev] [llvm-dev] Revisiting our informal policy to support two versions of MSVC

Robinson, Paul via cfe-dev cfe-dev at lists.llvm.org
Thu Sep 1 10:07:57 PDT 2016

Hi Reid, first off thanks *very* much for all your help fixing 2013-related problems.  We really appreciate it.

Let me propose a target date of September 15 for advancing the minimum MS compiler to VS2015 Update 3.  Certainly my team should be ready by then. If anybody else needs a later date, in particular people who own Windows bots still using VS2013, please speak up.

From: Reid Kleckner [mailto:rnk at google.com]
Sent: Wednesday, August 31, 2016 4:07 PM
To: Robinson, Paul
Cc: James Molloy; Nico Weber; llvm-dev; cfe-dev at lists.llvm.org
Subject: Re: [llvm-dev] [cfe-dev] Revisiting our informal policy to support two versions of MSVC

I'd like to revisit this. As a person who spends a fair amount of time monitoring our VS 2013 buildbots, I would say that I am ready to throw in the towel on MSVC 2013. Since this discussion, I have committed five (!) workarounds for MSVC 2013:

# in llvm
$ git log --author=rnk --grep=2013  --after='Aug 4 2016' --oneline
21a8ade Fix the MSVC 2013 build by using Elf_Word instead of making a local typedef
27e101d Revert "Add an optional parameter with a list of undefs to extendToIndices"
e8beddd Make vec_fabs.ll pass with MSVC 2013
ca77873 [AMDGPU] Give enum an explicit 64-bit type to fix MSVC 2013 failures

# in clang
$ git log --author=rnk --grep=2013  --after='Aug 4 2016' --oneline
18235a5 Try to work around an MSVC 2013 bug around defaulted default ctors

I'm pretty sure I'm missing instances where I helped others commit workarounds as well. So, I'd really like to drop 2013, probably sometime next month.

That said, I'd also like to echo Paul's sentiment that it'd help if people were less adventurous in their uses of C++11. New language features may look nice, but ultimately you may end up wasting my time and yours when I come and revert your change.

On Thu, Aug 4, 2016 at 7:52 AM, Robinson, Paul via llvm-dev <llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>> wrote:
I've heard from another group within Sony that they had "a number of problems" with VS2015 update 2, and strongly recommend going straight to update 3.  My immediate team has initiated a request but it hasn't gone through yet.

From: James Molloy [mailto:james at jamesmolloy.co.uk<mailto:james at jamesmolloy.co.uk>]
Sent: Wednesday, August 03, 2016 1:54 AM
To: Nico Weber; Robinson, Paul
Cc: llvm-dev; cfe-dev at lists.llvm.org<mailto:cfe-dev at lists.llvm.org>
Subject: Re: [cfe-dev] [llvm-dev] Revisiting our informal policy to support two versions of MSVC


This sounds like a decent idea to me. However we use 2013 for all our windows builds at the moment and it will take around 2 weeks to upgrade the installations on our cluster. We're pushing this hard to get it done soon so we don't get caught short, but a grace period would be much appreciated.



On Tue, 2 Aug 2016 at 21:24 Nico Weber via cfe-dev <cfe-dev at lists.llvm.org<mailto:cfe-dev at lists.llvm.org>> wrote:
On Tue, Aug 2, 2016 at 3:49 PM, Robinson, Paul via cfe-dev <cfe-dev at lists.llvm.org<mailto:cfe-dev at lists.llvm.org>> wrote:
For my project, timing is everything.  We (and I could easily imagine,
for many downstream projects) lead time is important.

In Chromium land, we've so far been able to use the same compiler we use to build Chrome to build clang. Currently that's MSVS2015 update 2, and it took quite a while to update from 2013 to 2015 due bugs in 2015 and whatnot. So I agree that it's useful to support older MSVS versions for some time. For this reason, requiring update 3 would be inconvenient for us, but 2015u2 would be no problem by now. It would've been a problem if 2015 had been required shortly after it was released.

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