llvm dev - Sep 2016 - [cfe-dev] Revisiting our informal policy to support two versions of MSVC

I don't see how the policy of supporting 2 versions is related to that
difficulty though. Whether we support 1 versions or 2 versions, 1 version
is still going to be deprecated every time a new version is released. So
this burden on upgrading buildbots doesn't seem to be much different.

As long as chromium compiler version is not tied to llvm compiler version
(and if it did, that would be a chromium decision not an llvm one) this is
always going to be a problem whether llvm supports newest compiler or
newest 2 compilers
On Thu, Sep 1, 2016 at 12:09 PM Nico Weber <thakis at chromium.org> wrote:
> On Thu, Sep 1, 2016 at 3:03 PM, Zachary Turner <zturner at
google.com> wrote:
>
>> I frequently see mention of how upgrading is problematic, is there
anyone
>> here for whom upgrading msvc versions is problematic? It seems like we
keep
>> talking in hypotheticals, but I'd like to hear from someone for
whom it is
>> *actually* a problem, and why.
>>
>> Vs community is permissive enough now that licensing isn't an
issue. And
>> every time this comes up it seems like we're saying "well it
could be hard
>> for people..." but nobody ever says it actually is hard for them
>> specifically
>>
>
> I just said that in the mail you're replying to (?) Having to update
our
> ~20 Windows bots so that they use a different MSVC than what's on there
> already for Chromium is going to be actually hard for us.
>
>
>> On Thu, Sep 1, 2016 at 11:16 AM Aaron Ballman via cfe-dev <
>> cfe-dev at lists.llvm.org> wrote:
>>
>>> On Thu, Sep 1, 2016 at 2:08 PM, Nico Weber <thakis at
chromium.org> wrote:
>>> > On Thu, Sep 1, 2016 at 1:30 PM, Aaron Ballman <aaron at
aaronballman.com>
>>> > wrote:
>>> >>
>>> >> On Thu, Sep 1, 2016 at 1:23 PM, Nico Weber via cfe-dev
>>> >> <cfe-dev at lists.llvm.org> wrote:
>>> >> > As mentioned upthread, we're still on update 2
for various reasons.
>>> >>
>>> >> Do you mind elaborating on those reasons?
>>> >
>>> >
>>> > Off the top of my head, clang-cl couldn't handle the code
generated by
>>> the
>>> > midl compiler in that version until fairly recently, and
we've been
>>> seeing
>>> > link.exe /INCREMENTAL failing intermittently (no reliable
repro case
>>> > though).
>>>
>>> Thank you for the extra information.
>>>
>>> >
>>> >>
>>> >> I think we should require
>>> >> the latest updates to MSVC due to the number of issues the
updates fix
>>> >> (esp regarding the newer language features that people
keep using so
>>> >> frequently), but I've also not heard a concrete use
case as to why we
>>> >> shouldn't.
>>> >
>>> >
>>> > Do you mean "require latest updates" in general, or
just in this case?
>>> > Updating immediately every time a new MSVS release comes out
would
>>> > definitely be tricky for us.
>>>
>>> I mean in general, but "immediate" wasn't what I had
in mind. More
>>> like "within some reasonable time frame", for whatever
definition of
>>> reasonable works for people. Given how often Microsoft fixes
critical
>>> language bugs with newer features during an Update release, I'm
hoping
>>> we can avoid sticking to older Updates if we are able to do so.
>>>
>>> ~Aaron
>>>
>>> >
>>> >>
>>> >>
>>> >> ~Aaron
>>> >>
>>> >> >
>>> >> > On Thu, Sep 1, 2016 at 1:07 PM, Robinson, Paul <
>>> paul.robinson at sony.com>
>>> >> > wrote:
>>> >> >>
>>> >> >> 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.
>>> >> >>
>>> >> >> --paulr
>>> >> >>
>>> >> >>
>>> >> >>
>>> >> >> 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> 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.
>>> >> >>
>>> >> >> --paulr
>>> >> >>
>>> >> >>
>>> >> >>
>>> >> >> From: James Molloy [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
>>> >> >> Subject: Re: [cfe-dev] [llvm-dev] Revisiting our
informal policy to
>>> >> >> support two versions of MSVC
>>> >> >>
>>> >> >>
>>> >> >>
>>> >> >> Hi,
>>> >> >>
>>> >> >>
>>> >> >>
>>> >> >> 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.
>>> >> >>
>>> >> >>
>>> >> >>
>>> >> >> Cheers,
>>> >> >>
>>> >> >>
>>> >> >>
>>> >> >> James
>>> >> >>
>>> >> >>
>>> >> >>
>>> >> >> On Tue, 2 Aug 2016 at 21:24 Nico Weber via
cfe-dev
>>> >> >> <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> 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.
>>> >> >>
>>> >> >>
>>> >> >>
>>> >> >> Nico
>>> >> >>
>>> >> >> _______________________________________________
>>> >> >> cfe-dev mailing list
>>> >> >> cfe-dev at lists.llvm.org
>>> >> >>
http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>> >> >>
>>> >> >>
>>> >> >> _______________________________________________
>>> >> >> LLVM Developers mailing list
>>> >> >> llvm-dev at lists.llvm.org
>>> >> >>
http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>> >> >>
>>> >> >>
>>> >> >
>>> >> >
>>> >> >
>>> >> > _______________________________________________
>>> >> > cfe-dev mailing list
>>> >> > cfe-dev at lists.llvm.org
>>> >> >
http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>> >> >
>>> >
>>> >
>>> _______________________________________________
>>> cfe-dev mailing list
>>> cfe-dev at lists.llvm.org
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>>
>>
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On Thu, Sep 1, 2016 at 3:16 PM, Zachary Turner <zturner at google.com>
wrote:
> I don't see how the policy of supporting 2 versions is related to that
> difficulty though. Whether we support 1 versions or 2 versions, 1 version
> is still going to be deprecated every time a new version is released. So
> this burden on upgrading buildbots doesn't seem to be much different.
>
> As long as chromium compiler version is not tied to llvm compiler version
> (and if it did, that would be a chromium decision not an llvm one) this is
> always going to be a problem whether llvm supports newest compiler or
> newest 2 compilers

I think in general the world is trying to update to new toolchains, it just
takes a while. With LLVM's old policy, Chromium always updated faster than
LLVM so far.

>
> On Thu, Sep 1, 2016 at 12:09 PM Nico Weber <thakis at chromium.org>
wrote:
>
>> On Thu, Sep 1, 2016 at 3:03 PM, Zachary Turner <zturner at
google.com>
>> wrote:
>>
>>> I frequently see mention of how upgrading is problematic, is there
>>> anyone here for whom upgrading msvc versions is problematic? It
seems like
>>> we keep talking in hypotheticals, but I'd like to hear from
someone for
>>> whom it is *actually* a problem, and why.
>>>
>>> Vs community is permissive enough now that licensing isn't an
issue. And
>>> every time this comes up it seems like we're saying "well
it could be hard
>>> for people..." but nobody ever says it actually is hard for
them
>>> specifically
>>>
>>
>> I just said that in the mail you're replying to (?) Having to
update our
>> ~20 Windows bots so that they use a different MSVC than what's on
there
>> already for Chromium is going to be actually hard for us.
>>
>>
>>> On Thu, Sep 1, 2016 at 11:16 AM Aaron Ballman via cfe-dev <
>>> cfe-dev at lists.llvm.org> wrote:
>>>
>>>> On Thu, Sep 1, 2016 at 2:08 PM, Nico Weber <thakis at
chromium.org> wrote:
>>>> > On Thu, Sep 1, 2016 at 1:30 PM, Aaron Ballman <aaron at
aaronballman.com
>>>> >
>>>> > wrote:
>>>> >>
>>>> >> On Thu, Sep 1, 2016 at 1:23 PM, Nico Weber via cfe-dev
>>>> >> <cfe-dev at lists.llvm.org> wrote:
>>>> >> > As mentioned upthread, we're still on update
2 for various reasons.
>>>> >>
>>>> >> Do you mind elaborating on those reasons?
>>>> >
>>>> >
>>>> > Off the top of my head, clang-cl couldn't handle the
code generated
>>>> by the
>>>> > midl compiler in that version until fairly recently, and
we've been
>>>> seeing
>>>> > link.exe /INCREMENTAL failing intermittently (no reliable
repro case
>>>> > though).
>>>>
>>>> Thank you for the extra information.
>>>>
>>>> >
>>>> >>
>>>> >> I think we should require
>>>> >> the latest updates to MSVC due to the number of issues
the updates
>>>> fix
>>>> >> (esp regarding the newer language features that people
keep using so
>>>> >> frequently), but I've also not heard a concrete
use case as to why we
>>>> >> shouldn't.
>>>> >
>>>> >
>>>> > Do you mean "require latest updates" in general,
or just in this case?
>>>> > Updating immediately every time a new MSVS release comes
out would
>>>> > definitely be tricky for us.
>>>>
>>>> I mean in general, but "immediate" wasn't what I
had in mind. More
>>>> like "within some reasonable time frame", for
whatever definition of
>>>> reasonable works for people. Given how often Microsoft fixes
critical
>>>> language bugs with newer features during an Update release,
I'm hoping
>>>> we can avoid sticking to older Updates if we are able to do so.
>>>>
>>>> ~Aaron
>>>>
>>>> >
>>>> >>
>>>> >>
>>>> >> ~Aaron
>>>> >>
>>>> >> >
>>>> >> > On Thu, Sep 1, 2016 at 1:07 PM, Robinson, Paul
<
>>>> paul.robinson at sony.com>
>>>> >> > wrote:
>>>> >> >>
>>>> >> >> 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.
>>>> >> >>
>>>> >> >> --paulr
>>>> >> >>
>>>> >> >>
>>>> >> >>
>>>> >> >> 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> 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.
>>>> >> >>
>>>> >> >> --paulr
>>>> >> >>
>>>> >> >>
>>>> >> >>
>>>> >> >> From: James Molloy [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
>>>> >> >> Subject: Re: [cfe-dev] [llvm-dev] Revisiting
our informal policy
>>>> to
>>>> >> >> support two versions of MSVC
>>>> >> >>
>>>> >> >>
>>>> >> >>
>>>> >> >> Hi,
>>>> >> >>
>>>> >> >>
>>>> >> >>
>>>> >> >> 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.
>>>> >> >>
>>>> >> >>
>>>> >> >>
>>>> >> >> Cheers,
>>>> >> >>
>>>> >> >>
>>>> >> >>
>>>> >> >> James
>>>> >> >>
>>>> >> >>
>>>> >> >>
>>>> >> >> On Tue, 2 Aug 2016 at 21:24 Nico Weber via
cfe-dev
>>>> >> >> <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> 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.
>>>> >> >>
>>>> >> >>
>>>> >> >>
>>>> >> >> Nico
>>>> >> >>
>>>> >> >>
_______________________________________________
>>>> >> >> cfe-dev mailing list
>>>> >> >> cfe-dev at lists.llvm.org
>>>> >> >>
http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>>> >> >>
>>>> >> >>
>>>> >> >>
_______________________________________________
>>>> >> >> LLVM Developers mailing list
>>>> >> >> llvm-dev at lists.llvm.org
>>>> >> >>
http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>> >> >>
>>>> >> >>
>>>> >> >
>>>> >> >
>>>> >> >
>>>> >> > _______________________________________________
>>>> >> > cfe-dev mailing list
>>>> >> > cfe-dev at lists.llvm.org
>>>> >> >
http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>>> >> >
>>>> >
>>>> >
>>>> _______________________________________________
>>>> cfe-dev mailing list
>>>> cfe-dev at lists.llvm.org
>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>>>
>>>
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I guess what I'm getting at, is why do we even need to support 2 toolchains
with LLVM *at all*?  Why can't we just always upgrade to the newest one
unless there are serious issues with it?

There used to be two reasons that I'm aware of:

1) Licensing.  Community used to be Express, and Express used to be limited
in functionality.  But this is no longer the case.  Community is fine for
anyone to use, even corporations, for free, as long as it is for an open
source project.  IANAL, but it says it in Section 1.b.1 here
<https://www.visualstudio.com/support/legal/mt171547>.

2) Library toolchain mismatches.  It used to be that in order to link
against a library, it had to be compiled with the same toolchain.  So
someone whose application was built with VS 2012 couldn't link against LLVM
built with VS 2013, they would have to build LLVM themselves with VS2012,
so dropping support for 2012 would harm them.

But beginning with Visual Studio 2015, because of the UCRT, this is no
longer the case.  All versions of the CRT will be forward compatible.

So if we're going to upgrade to VS 2015, why not also just upgrade to VS 15
as soon as possible?  Once VS 2015 is the minimum, it doesn't seem like we
should worry too much about upgrading compiler versions anymore (aside from
the effort to actually do it and make sure it works and the compiler bugs
and issues are known about).

On Thu, Sep 1, 2016 at 12:24 PM Nico Weber <thakis at chromium.org> wrote:
> On Thu, Sep 1, 2016 at 3:16 PM, Zachary Turner <zturner at
google.com> wrote:
>
>> I don't see how the policy of supporting 2 versions is related to
that
>> difficulty though. Whether we support 1 versions or 2 versions, 1
version
>> is still going to be deprecated every time a new version is released.
So
>> this burden on upgrading buildbots doesn't seem to be much
different.
>>
>> As long as chromium compiler version is not tied to llvm compiler
version
>> (and if it did, that would be a chromium decision not an llvm one) this
is
>> always going to be a problem whether llvm supports newest compiler or
>> newest 2 compilers
>
>
> I think in general the world is trying to update to new toolchains, it
> just takes a while. With LLVM's old policy, Chromium always updated
faster
> than LLVM so far.
>
>
>>
>> On Thu, Sep 1, 2016 at 12:09 PM Nico Weber <thakis at
chromium.org> wrote:
>>
>>> On Thu, Sep 1, 2016 at 3:03 PM, Zachary Turner <zturner at
google.com>
>>> wrote:
>>>
>>>> I frequently see mention of how upgrading is problematic, is
there
>>>> anyone here for whom upgrading msvc versions is problematic? It
seems like
>>>> we keep talking in hypotheticals, but I'd like to hear from
someone for
>>>> whom it is *actually* a problem, and why.
>>>>
>>>> Vs community is permissive enough now that licensing isn't
an issue.
>>>> And every time this comes up it seems like we're saying
"well it could be
>>>> hard for people..." but nobody ever says it actually is
hard for them
>>>> specifically
>>>>
>>>
>>> I just said that in the mail you're replying to (?) Having to
update our
>>> ~20 Windows bots so that they use a different MSVC than what's
on there
>>> already for Chromium is going to be actually hard for us.
>>>
>>>
>>>> On Thu, Sep 1, 2016 at 11:16 AM Aaron Ballman via cfe-dev <
>>>> cfe-dev at lists.llvm.org> wrote:
>>>>
>>>>> On Thu, Sep 1, 2016 at 2:08 PM, Nico Weber <thakis at
chromium.org>
>>>>> wrote:
>>>>> > On Thu, Sep 1, 2016 at 1:30 PM, Aaron Ballman <
>>>>> aaron at aaronballman.com>
>>>>> > wrote:
>>>>> >>
>>>>> >> On Thu, Sep 1, 2016 at 1:23 PM, Nico Weber via
cfe-dev
>>>>> >> <cfe-dev at lists.llvm.org> wrote:
>>>>> >> > As mentioned upthread, we're still on
update 2 for various
>>>>> reasons.
>>>>> >>
>>>>> >> Do you mind elaborating on those reasons?
>>>>> >
>>>>> >
>>>>> > Off the top of my head, clang-cl couldn't handle
the code generated
>>>>> by the
>>>>> > midl compiler in that version until fairly recently,
and we've been
>>>>> seeing
>>>>> > link.exe /INCREMENTAL failing intermittently (no
reliable repro case
>>>>> > though).
>>>>>
>>>>> Thank you for the extra information.
>>>>>
>>>>> >
>>>>> >>
>>>>> >> I think we should require
>>>>> >> the latest updates to MSVC due to the number of
issues the updates
>>>>> fix
>>>>> >> (esp regarding the newer language features that
people keep using so
>>>>> >> frequently), but I've also not heard a
concrete use case as to why
>>>>> we
>>>>> >> shouldn't.
>>>>> >
>>>>> >
>>>>> > Do you mean "require latest updates" in
general, or just in this
>>>>> case?
>>>>> > Updating immediately every time a new MSVS release
comes out would
>>>>> > definitely be tricky for us.
>>>>>
>>>>> I mean in general, but "immediate" wasn't
what I had in mind. More
>>>>> like "within some reasonable time frame", for
whatever definition of
>>>>> reasonable works for people. Given how often Microsoft
fixes critical
>>>>> language bugs with newer features during an Update release,
I'm hoping
>>>>> we can avoid sticking to older Updates if we are able to do
so.
>>>>>
>>>>> ~Aaron
>>>>>
>>>>> >
>>>>> >>
>>>>> >>
>>>>> >> ~Aaron
>>>>> >>
>>>>> >> >
>>>>> >> > On Thu, Sep 1, 2016 at 1:07 PM, Robinson,
Paul <
>>>>> paul.robinson at sony.com>
>>>>> >> > wrote:
>>>>> >> >>
>>>>> >> >> 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.
>>>>> >> >>
>>>>> >> >> --paulr
>>>>> >> >>
>>>>> >> >>
>>>>> >> >>
>>>>> >> >> 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> 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.
>>>>> >> >>
>>>>> >> >> --paulr
>>>>> >> >>
>>>>> >> >>
>>>>> >> >>
>>>>> >> >> From: James Molloy [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
>>>>> >> >> Subject: Re: [cfe-dev] [llvm-dev]
Revisiting our informal policy
>>>>> to
>>>>> >> >> support two versions of MSVC
>>>>> >> >>
>>>>> >> >>
>>>>> >> >>
>>>>> >> >> Hi,
>>>>> >> >>
>>>>> >> >>
>>>>> >> >>
>>>>> >> >> 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.
>>>>> >> >>
>>>>> >> >>
>>>>> >> >>
>>>>> >> >> Cheers,
>>>>> >> >>
>>>>> >> >>
>>>>> >> >>
>>>>> >> >> James
>>>>> >> >>
>>>>> >> >>
>>>>> >> >>
>>>>> >> >> On Tue, 2 Aug 2016 at 21:24 Nico Weber
via cfe-dev
>>>>> >> >> <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> 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.
>>>>> >> >>
>>>>> >> >>
>>>>> >> >>
>>>>> >> >> Nico
>>>>> >> >>
>>>>> >> >>
_______________________________________________
>>>>> >> >> cfe-dev mailing list
>>>>> >> >> cfe-dev at lists.llvm.org
>>>>> >> >>
http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>>>> >> >>
>>>>> >> >>
>>>>> >> >>
_______________________________________________
>>>>> >> >> LLVM Developers mailing list
>>>>> >> >> llvm-dev at lists.llvm.org
>>>>> >> >>
http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>> >> >>
>>>>> >> >>
>>>>> >> >
>>>>> >> >
>>>>> >> >
>>>>> >> >
_______________________________________________
>>>>> >> > cfe-dev mailing list
>>>>> >> > cfe-dev at lists.llvm.org
>>>>> >> >
http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>>>> >> >
>>>>> >
>>>>> >
>>>>> _______________________________________________
>>>>> cfe-dev mailing list
>>>>> cfe-dev at lists.llvm.org
>>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>>>>
>>>>
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