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

[Aaron Ballman]

On Mon, Feb 16, 2015 at 2:42 PM, Chris Bieneman <beanz at apple.com> wrote:
>
>> On Feb 16, 2015, at 10:47 AM, Aaron Ballman <aaron at aaronballman.com> wrote:
>>
>> On Mon, Feb 16, 2015 at 1:37 PM, Chris Bieneman <beanz at apple.com> wrote:
>>> The plan as stated was:
>>>
>>> 1) Loop in cfe-dev and lldb-dev (Done!)
>>> 2) Wait until this email fully circulates in digests and LLVM Weekly so that everyone who has an objection can voice it
>>> 3) If there are no objections, Commit a change to the CMake build which errors on old MSVC versions
>>> 4) Revert and fix buildbots
>>> 5) Repeat 3 & 4 until no issues
>>
>> It's my understanding that we're past step 5 currently, and waiting to
>> do step 6.
>
> When I landed the change originally I saw no failures from any public bots. I assume Takumi reverted it because there was a failure on a non-public bot. Since the change re-landed on Sunday, I don’t think it is really safe to assume all non-public bots had been migrated.

Takumi's bots are public bots: http://bb.pgr.jp/builders. They also
happily alert folks in IRC.

> I’m not trying to stand in the way of progress here, but I do feel like we’ve kinda thrown the plan to the wind here.

I think we're following different plans; I think the progress d0k and
I have made was done following the plan. I may be wrong with my
understanding of the plan, however.

>
>>
>>> 6) Once the change is live for a week with no issues, update the documentation to reflect the minimum required MSVC version as 2013
>>>
>>> This really doesn’t make sense if we are landing changes requiring MSVC 2013 between steps 3&5. Reverting as needed now that we have a stack of changes that is piling up isn’t really viable anymore.
>>
>> You are correct, if we need to revert, it would be challenging. My
>> understanding is that we do not need to revert any further, as
>> Chapuni's bots were the last ones that needed specific attention. The
>> lld and lldb bots may require further attention, but not certain
>> whether they require this change to be reverted? Those owners would
>> have to speak up with what they'd like to see happen.
>
> Hopefull there are no issues, but since this was re-landed on a Sunday when a lot of people aren’t around and watching I’m nervous that we may have broken things when people weren’t looking.

I've not seen any bot-related issues arise in email or IRC yet, and I
suspect we would have tickled *something* by now if there were major
problems.

>
>>
>>> So I assume the new plan to just make anyone using MSVC update or they can’t build anymore.
>>
>> They couldn't build after step 3 anyway (almost any source changes
>> require CMake to rebuild the solutions, so any source fetches getting
>> newer code would also get the CMake files requiring a newer version of
>> MSVC before the solution can be generated). The repetition part of the
>> above steps is for build bots, not all users (though, obviously, if
>> there are major users who are stuck and didn't realize it until now,
>> we would have to figure out how to handle that).
>
> Right, but step 4 is to revert that change. We’ve now basically made it prohibitively difficult to revert.

Agreed.

> Look, I want to use variadic templates as much as the next guy, I’m just also wanting to be considerate of our unfortunate colleagues using MSVC.

As one of the people who was opposed to this change originally
specifically for that consideration, I appreciate it (though I would
not describe us as "unfortunate.")

~Aaron