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

[Chris Bieneman]

> On Feb 16, 2015, at 11:53 AM, Aaron Ballman <aaron at aaronballman.com> wrote:
> 
> On Mon, Feb 16, 2015 at 2:42 PM, Chris Bieneman <beanz at apple.com <mailto: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 <http://bb.pgr.jp/builders>. They also
> happily alert folks in IRC.

I’m aware of all this, and was on IRC when I landed the change on Friday, which is why I was surprised when I didn’t see any failures, but my commit was still reverted (hence my comment about assuming it was non-public).

> 
>> 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.

I definitely think we had different interpretations of the plan. Maybe we should be more explicit about timelines for transitions like this in the future.

> 
>> 
>>> 
>>>> 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.

I think you’re right, that at this point we are probably safe to assume all is well in the world. I didn’t really feel that this was the case when I started sending emails on this thread earlier this morning. I’m not sure what things are like in your office, but Apple’s campus is a bit of a ghost town before 10am on Monday mornings.

> 
>> 
>>> 
>>>> 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.”)

Don’t take it personally. I kinda view anyone not using Vim and Ninja as their development environment as impoverished :-).

-Chris

> 
> ~Aaron

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