[PATCH] D42762: Rewrite the VS Integration Scripts

[Nico Weber via llvm-commits]

Anyhoo, to move this along, maybe put the rewriting part into a different
diff. There's probably agreement on the vast majority of this diff :-)

On Fri, Feb 2, 2018 at 12:30 PM, Nico Weber <thakis at chromium.org> wrote:

> I'm not saying a corrupt file, but an empty valid pdb file.
>
> Trying to be compatible with cl means being compatible with its observable
> effects as far as reasonable.
>
> On Fri, Feb 2, 2018 at 12:27 PM, Zachary Turner <zturner at google.com>
> wrote:
>
>> I would also argue that clang-cl only tries to be compatible **with
>> cl**.  Not with every possible build system that might support cl.  The
>> compiler should not be be trying to support the build system, it's the
>> other way around.
>>
>> On Fri, Feb 2, 2018 at 9:24 AM Zachary Turner <zturner at google.com> wrote:
>>
>>> I disagree with this.  We should not be putting emitting a corrupt file
>>> under any circumstances.  That's even worse for compatibility than doing
>>> nothing.
>>>
>>> On Fri, Feb 2, 2018 at 9:24 AM Zachary Turner <zturner at google.com>
>>> wrote:
>>>
>>>> I tested and CMake is buggy with respect to how it handles /Zi (perhaps
>>>> it's an intentional tradeoff, I don't know).  Steps to reproduce this test:
>>>>
>>>> 1) Build obj2yaml from LLVM using CMake and cl
>>>> 2) delete tools\obj2yaml\CMakeFiles\obj2yaml.dir\vc140.pdb
>>>> 3) delete tools\obj2yaml\CMakeFiles\obj2yaml.dir\coff2yaml.pdb
>>>> 4) delete bin\obj2yaml.pdb
>>>> 5) ninja obj2yaml
>>>>
>>>> You'll get these warnings:
>>>> LINK : program database D:\src\llvmbuild\cl\Debug\x64\bin\obj2yaml.pdb
>>>> missing; performing full link
>>>> obj2yaml.cpp.obj : warning LNK4099: PDB 'vc140.pdb' was not found with
>>>> 'obj2yaml.cpp.obj' or at 'D:\src\llvmbuild\cl\Debug\x64\bin\vc140.pdb';
>>>> linking object as if no debug info
>>>> dwarf2yaml.cpp.obj : warning LNK4099: PDB 'vc140.pdb' was not found
>>>> with 'dwarf2yaml.cpp.obj' or at 'D:\src\llvmbuild\cl\Debug\x64\bin\vc140.pdb';
>>>> linking object as if no debug info
>>>> elf2yaml.cpp.obj : warning LNK4099: PDB 'vc140.pdb' was not found with
>>>> 'elf2yaml.cpp.obj' or at 'D:\src\llvmbuild\cl\Debug\x64\bin\vc140.pdb';
>>>> linking object as if no debug info
>>>> macho2yaml.cpp.obj : warning LNK4099: PDB 'vc140.pdb' was not found
>>>> with 'macho2yaml.cpp.obj' or at 'D:\src\llvmbuild\cl\Debug\x64\bin\vc140.pdb';
>>>> linking object as if no debug info
>>>> wasm2yaml.cpp.obj : warning LNK4099: PDB 'vc140.pdb' was not found with
>>>> 'wasm2yaml.cpp.obj' or at 'D:\src\llvmbuild\cl\Debug\x64\bin\vc140.pdb';
>>>> linking object as if no debug info
>>>> Error.cpp.obj : warning LNK4099: PDB 'vc140.pdb' was not found with
>>>> 'Error.cpp.obj' or at 'D:\src\llvmbuild\cl\Debug\x64\bin\vc140.pdb';
>>>> linking object as if no debug info
>>>>
>>>> What it should be doing is saying that every cpp file, in addition to
>>>> $(FileName).obj, also produces vc140.pdb.  MSBuild gets this correct
>>>>
>>>> On Fri, Feb 2, 2018 at 9:05 AM Zachary Turner <zturner at google.com>
>>>> wrote:
>>>>
>>>>> It’s an additional pdb, which the linker then uses as an input. The
>>>>> linker still writes the final pdb. The msbuild task that actually invokes
>>>>> cl.exe is implemented in a dll, so we can only observe its effects.
>>>>>
>>>>> I’m not sure how cmake is implemented, but this is really a build
>>>>> system issue of inputs, outputs, and dependencies. If cmake does have
>>>>> issues, patching cmake seems like the appropriate solution.
>>>>> On Fri, Feb 2, 2018 at 8:54 AM Hans Wennborg <hans at chromium.org>
>>>>> wrote:
>>>>>
>>>>>> I'd still like to understand how msbuild.exe is running the build to
>>>>>> expect vc140.pdb to be written, and why we're outputing the .pdb file
>>>>>> in the wrong place. Or is vc140.pdb some additional pdb that's
>>>>>> supposed to get output on the side?
>>>>>>
>>>>>> I don't like the idea of the vs integration rewriting flags. What
>>>>>> about users not using msbuild but cmake? Should cmake start rewriting
>>>>>> flags for clang-cl too?
>>>>>>
>>>>>> On Fri, Feb 2, 2018 at 5:49 PM, Zachary Turner <zturner at google.com>
>>>>>> wrote:
>>>>>> > That’s why we unset the option in msbuild, so it no longer expects
>>>>>> that. The
>>>>>> > current solution makes it behave exactly as if /Z7 had been chosen
>>>>>> in the
>>>>>> > UI. Having the compiler write a type server pdb seems like an
>>>>>> enormous
>>>>>> > amount of work, and writing a 0 byte file seems odd.
>>>>>> >
>>>>>> > On Fri, Feb 2, 2018 at 8:46 AM Hans Wennborg <hans at chromium.org>
>>>>>> wrote:
>>>>>> >>
>>>>>> >> But if the build system invokes the compiler + linker, expects to
>>>>>> end
>>>>>> >> up with vc140.pdb but instead ends up with foo.pdb, maybe the
>>>>>> compiler
>>>>>> >> + linker is not interpreting the flags passed from the build system
>>>>>> >> correctly.
>>>>>> >>
>>>>>> >> On Fri, Feb 2, 2018 at 5:44 PM, Zachary Turner <zturner at google.com>
>>>>>> wrote:
>>>>>> >> > Also, since this is a build system issue and not a compiler
>>>>>> issue, it
>>>>>> >> > seems
>>>>>> >> > intuitive to me to deal with it at the build system level
>>>>>> >> > On Fri, Feb 2, 2018 at 8:42 AM Zachary Turner <
>>>>>> zturner at google.com>
>>>>>> >> > wrote:
>>>>>> >> >>
>>>>>> >> >> It’s a compiler generated pdb, /Zi means “all compiler
>>>>>> processes should
>>>>>> >> >> write to the same pdb”, whereas /Z7 means “put the debug info
>>>>>> in the
>>>>>> >> >> object
>>>>>> >> >> files instead”. If the user does a clean build the file will get
>>>>>> >> >> deleted and
>>>>>> >> >> there won’t even be anything to touch. The file name comes from
>>>>>> another
>>>>>> >> >> flag
>>>>>> >> >> (/Fo or /Fd, can’t remember) which msbuild defaults to
>>>>>> vc$(ToolsetName)
>>>>>> >> >> On Fri, Feb 2, 2018 at 8:36 AM Hans Wennborg <hans at chromium.org>
>>>>>> wrote:
>>>>>> >> >>>
>>>>>> >> >>> Yes, but I'd like to understand exactly why. Where does the
>>>>>> name
>>>>>> >> >>> vc140.pdb come from? What is supposed to go into this file?
>>>>>> Maybe
>>>>>> >> >>> clang-cl should touch it when invoked with /Zi?
>>>>>> >> >>>
>>>>>> >> >>> On Fri, Feb 2, 2018 at 5:32 PM, Zachary Turner <
>>>>>> zturner at google.com>
>>>>>> >> >>> wrote:
>>>>>> >> >>> > Symptom: when /Zi is selected, VS always rebuilds all source
>>>>>> files,
>>>>>> >> >>> > even if
>>>>>> >> >>> > just 1 (possibly even none) have changed.
>>>>>> >> >>> >
>>>>>> >> >>> > Fix: Change /Zi to /Z7 in the UI
>>>>>> >> >>> >
>>>>>> >> >>> > More details here: https://bugs.llvm.org/show_bug
>>>>>> .cgi?id=36140
>>>>>> >> >>> >
>>>>>> >> >>> > On Fri, Feb 2, 2018 at 8:12 AM Hans Wennborg <
>>>>>> hans at chromium.org>
>>>>>> >> >>> > wrote:
>>>>>> >> >>> >>
>>>>>> >> >>> >> On Fri, Feb 2, 2018 at 4:40 PM, Zachary Turner <
>>>>>> zturner at google.com>
>>>>>> >> >>> >> wrote:
>>>>>> >> >>> >> >
>>>>>> >> >>> >> > On Fri, Feb 2, 2018 at 6:23 AM Hans Wennborg <
>>>>>> hans at chromium.org>
>>>>>> >> >>> >> > wrote:
>>>>>> >> >>> >> >>
>>>>>> >> >>> >> >> (Your reply didn't go to Phabricator, so re-adding folks
>>>>>> >> >>> >> >> subscribed
>>>>>> >> >>> >> >> there.)
>>>>>> >> >>> >> >>
>>>>>> >> >>> >> >> On Thu, Feb 1, 2018 at 9:08 PM, Zachary Turner via
>>>>>> llvm-commits
>>>>>> >> >>> >> >> <llvm-commits at lists.llvm.org> wrote:
>>>>>> >> >>> >> >> > I'm kind of imagining this world where we have one VS
>>>>>> >> >>> >> >> > Integration
>>>>>> >> >>> >> >> > that
>>>>>> >> >>> >> >> > works
>>>>>> >> >>> >> >> > no matter what version of LLVM you have.  The nice
>>>>>> thing about
>>>>>> >> >>> >> >> > this
>>>>>> >> >>> >> >> > is
>>>>>> >> >>> >> >> > that
>>>>>> >> >>> >> >> > it allows it to work with hermetic toolchains, older
>>>>>> versions
>>>>>> >> >>> >> >> > of
>>>>>> >> >>> >> >> > LLVM
>>>>>> >> >>> >> >> > that
>>>>>> >> >>> >> >> > may already be installed on a user's machine, local
>>>>>> dev builds
>>>>>> >> >>> >> >> > of
>>>>>> >> >>> >> >> > LLVM,
>>>>>> >> >>> >> >> > etc.
>>>>>> >> >>> >> >>
>>>>>> >> >>> >> >> I'm on board with this. It seems useful especially for
>>>>>> the case
>>>>>> >> >>> >> >> where
>>>>>> >> >>> >> >> the developer may have multiple LLVM toolchains
>>>>>> installed and
>>>>>> >> >>> >> >> want
>>>>>> >> >>> >> >> to
>>>>>> >> >>> >> >> point at a specific one. It would be nice if we could
>>>>>> still
>>>>>> >> >>> >> >> trigger
>>>>>> >> >>> >> >> the installation of the toolset when installing the LLVM
>>>>>> >> >>> >> >> toolchain
>>>>>> >> >>> >> >> though.
>>>>>> >> >>> >> >>
>>>>>> >> >>> >> >> But for the integration to work regardless of LLVM
>>>>>> version, I
>>>>>> >> >>> >> >> don't
>>>>>> >> >>> >> >> think the integration can bake in assumptions about what
>>>>>> flags
>>>>>> >> >>> >> >> clang-cl supports and re-map them etc. The set of flags
>>>>>> >> >>> >> >> supported
>>>>>> >> >>> >> >> by
>>>>>> >> >>> >> >> clang-cl and how they're handled changes frequently.
>>>>>> >> >>> >> >>
>>>>>> >> >>> >> >> I like the idea of a VS integration that's LLVM-version
>>>>>> >> >>> >> >> independent
>>>>>> >> >>> >> >> --
>>>>>> >> >>> >> >> the current one is almost that except for the baked in
>>>>>> version
>>>>>> >> >>> >> >> number
>>>>>> >> >>> >> >> -- but for it to work, I think it has to be really
>>>>>> simple,
>>>>>> >> >>> >> >> basically
>>>>>> >> >>> >> >> just pointing MSVC at clang-cl.exe and nothing more.
>>>>>> >> >>> >> >
>>>>>> >> >>> >> > I’ve already mentioned at least one case whereas this is
>>>>>> >> >>> >> > impossible
>>>>>> >> >>> >> > (/Zi
>>>>>> >> >>> >> > vs
>>>>>> >> >>> >> > /Z7), and given that there are thousands of lines of
>>>>>> msbuild
>>>>>> >> >>> >> > logic
>>>>>> >> >>> >> > that
>>>>>> >> >>> >> > are
>>>>>> >> >>> >> > running and processing these options before they make it
>>>>>> to
>>>>>> >> >>> >> > clang-cl,
>>>>>> >> >>> >> > I’m
>>>>>> >> >>> >> > certain there are more that we don’t yet know about.
>>>>>> >> >>> >>
>>>>>> >> >>> >> I'd like to understand the /Zi vs /Z7 thing better. Can you
>>>>>> ELI5
>>>>>> >> >>> >> the
>>>>>> >> >>> >> problem?
>>>>>> >> >>> >>
>>>>>> >> >>> >>
>>>>>> >> >>> >> >
>>>>>> >> >>> >> > Simple is nice, I don’t disagree with that, but not at the
>>>>>> >> >>> >> > expense
>>>>>> >> >>> >> > of
>>>>>> >> >>> >> > user
>>>>>> >> >>> >> > experience.  i still don’t think there’s any maintenance
>>>>>> issues
>>>>>> >> >>> >> > here
>>>>>> >> >>> >> > though.
>>>>>> >> >>> >> > I think the current version here could probably sit for
>>>>>> 5+ years
>>>>>> >> >>> >> > and
>>>>>> >> >>> >> > never
>>>>>> >> >>> >> > need to be touched, continuing to work both with future VS
>>>>>> >> >>> >> > versions
>>>>>> >> >>> >> > and
>>>>>> >> >>> >> > future clang-cl versions unmodified.
>>>>>> >> >>> >> >
>>>>>> >> >>> >> >
>>>>>> >> >>> >> >>
>>>>>> >> >>> >> >>
>>>>>> >> >>> >> >> > The only maintenance burden I can think of is one
>>>>>> where we
>>>>>> >> >>> >> >> > remove
>>>>>> >> >>> >> >> > or
>>>>>> >> >>> >> >> > add
>>>>>> >> >>> >> >> > flags in clang-cl, which doesn't happen very often, if
>>>>>> ever.
>>>>>> >> >>> >> >>
>>>>>> >> >>> >> >> It puzzles me that you think we rarely or ever change
>>>>>> the flags
>>>>>> >> >>> >> >> clang-cl supports or how they're handled. In my
>>>>>> experience, the
>>>>>> >> >>> >> >> flags
>>>>>> >> >>> >> >> change every release.
>>>>>> >> >>> >> >>
>>>>>> >> >>> >> >> >  Any flag that
>>>>>> >> >>> >> >> > is added to MSVC doesn't require any action from us.
>>>>>> >> >>> >> >>
>>>>>> >> >>> >> >> Depends on the flag, no?
>>>>>> >> >>> >> >
>>>>>> >> >>> >> > Not really.  Any flag that msvc adds, assuming we don’t
>>>>>> update
>>>>>> >> >>> >> > this
>>>>>> >> >>> >> > file,
>>>>>> >> >>> >> > gets passed through to clang-cl which is what you’re
>>>>>> proposing i
>>>>>> >> >>> >> > do
>>>>>> >> >>> >> > with
>>>>>> >> >>> >> > all
>>>>>> >> >>> >> > options anyway.
>>>>>> >> >>> >> >
>>>>>> >> >>> >> >
>>>>>> >> >>> >> >>
>>>>>> >> >>> >> >>
>>>>>> >> >>> >> >> > I plan to expose a UI for optimizations and warning,
>>>>>> so I
>>>>>> >> >>> >> >> > could
>>>>>> >> >>> >> >> > see a
>>>>>> >> >>> >> >> > maintenace burden when we add new -W or -f flags that
>>>>>> are not
>>>>>> >> >>> >> >> > exposed
>>>>>> >> >>> >> >> > to
>>>>>> >> >>> >> >> > the
>>>>>> >> >>> >> >> > UI.  But those can still be specified via additional
>>>>>> compiler
>>>>>> >> >>> >> >> > flags.
>>>>>> >> >>> >> >> > And
>>>>>> >> >>> >> >> > the maintenance burden is actually less than coupling
>>>>>> it to
>>>>>> >> >>> >> >> > the
>>>>>> >> >>> >> >> > installed
>>>>>> >> >>> >> >> > toolchain because we can do it at our leisure, rather
>>>>>> than
>>>>>> >> >>> >> >> > being
>>>>>> >> >>> >> >> > pressed
>>>>>> >> >>> >> >> > to
>>>>>> >> >>> >> >> > get it done by a release.
>>>>>> >> >>> >> >>
>>>>>> >> >>> >> >> But you're saying that the toolset should be independent
>>>>>> of the
>>>>>> >> >>> >> >> LLVM
>>>>>> >> >>> >> >> version? If we add a -Wfoobar flag in Clang x.y.z and
>>>>>> want to
>>>>>> >> >>> >> >> expose
>>>>>> >> >>> >> >> that in your UI, that UI then needs to be conditional on
>>>>>> what
>>>>>> >> >>> >> >> version
>>>>>> >> >>> >> >> of Clang it's targeting. Same thing if we remove -Wquux
>>>>>> in
>>>>>> >> >>> >> >> another
>>>>>> >> >>> >> >> Clang version. This sounds like a maintenance nightmare
>>>>>> to me.
>>>>>> >> >>> >> >
>>>>>> >> >>> >> > If we do nothing, any added -W options are still
>>>>>> available via
>>>>>> >> >>> >> > Additional
>>>>>> >> >>> >> > Compiler Flags.   So as with all the other custom logic
>>>>>> in the
>>>>>> >> >>> >> > msbuild
>>>>>> >> >>> >> > files, we’re still not obligated to maintain that, and it
>>>>>> will
>>>>>> >> >>> >> > still
>>>>>> >> >>> >> > continue to work fine
>>>>>> >> >>> >> >
>>>>>> >> >>> >> > For options that we remove, sure, we should update the
>>>>>> file.  One
>>>>>> >> >>> >> > way to
>>>>>> >> >>> >> > handle this would be to add a new version of clang-cl.xml
>>>>>> every
>>>>>> >> >>> >> > release,
>>>>>> >> >>> >> > and
>>>>>> >> >>> >> > conditionally include the proper xml file.  How
>>>>>> frequently do we
>>>>>> >> >>> >> > remove
>>>>>> >> >>> >> > warnings though?  Doing so would cause people’s builds to
>>>>>> break
>>>>>> >> >>> >> > because
>>>>>> >> >>> >> > they’d be passing unrecognized options, so I suspect it’s
>>>>>> almost
>>>>>> >> >>> >> > never.
>>>>>> >> >>> >> >
>>>>>> >> >>> >> > Of all the things though, this is the one that I think
>>>>>> it’s most
>>>>>> >> >>> >> > important
>>>>>> >> >>> >> > to accept the maintenance burden of.  This is the
>>>>>> difference
>>>>>> >> >>> >> > between
>>>>>> >> >>> >> > “we
>>>>>> >> >>> >> > put
>>>>>> >> >>> >> > the minimum amount of work possible into getting this
>>>>>> working so
>>>>>> >> >>> >> > we
>>>>>> >> >>> >> > could do
>>>>>> >> >>> >> > other things” and “we care about this, we made it as easy
>>>>>> as
>>>>>> >> >>> >> > possible to
>>>>>> >> >>> >> > use, we designed it with VS users in mind”.  As someone
>>>>>> who used
>>>>>> >> >>> >> > VS
>>>>>> >> >>> >> > through
>>>>>> >> >>> >> > the UI exclusively for over 15 years, there’s going to be
>>>>>> a huge
>>>>>> >> >>> >> > difference
>>>>>> >> >>> >> > between providing this feature and not providing it.
>>>>>> >> >>> >> >
>>>>>> >> >>> >> > I *still* don’t see the maintenance burden as being high
>>>>>> though.
>>>>>> >> >>> >> > We
>>>>>> >> >>> >> > can
>>>>>> >> >>> >> > release a new clang-cl.xml like every 2-3 years and it
>>>>>> would take
>>>>>> >> >>> >> > all of
>>>>>> >> >>> >> > 30
>>>>>> >> >>> >> > minutes to put it together and get it on the marketplace.
>>>>>> >> >>> >> >
>>>>>> >> >>> >> >
>>>>>> >> >>> >> >
>>>>>> >> >>> >> >>
>>>>>> >> >>> >> >>
>>>>>> >> >>> >> >>
>>>>>> >> >>> >> >> > One thing I could maybe do to lower the maintenance
>>>>>> burden a
>>>>>> >> >>> >> >> > little
>>>>>> >> >>> >> >> > is
>>>>>> >> >>> >> >> > to
>>>>>> >> >>> >> >> > try to have some better logic for detecting the clang
>>>>>> version.
>>>>>> >> >>> >> >> > We
>>>>>> >> >>> >> >> > were
>>>>>> >> >>> >> >> > already using the registry before anyway to find the
>>>>>> installed
>>>>>> >> >>> >> >> > LLVM,
>>>>>> >> >>> >> >> > maybe
>>>>>> >> >>> >> >> > there's a way for me to just figure out the version
>>>>>> without
>>>>>> >> >>> >> >> > the
>>>>>> >> >>> >> >> > additional
>>>>>> >> >>> >> >> > registry value.  I'll have to look into that though.
>>>>>> >> >>> >> >> >
>>>>>> >> >>> >> >> >
>>>>>> >> >>> >> >> >
>>>>>> >> >>> >> >> > On Thu, Feb 1, 2018 at 11:09 AM Zachary Turner
>>>>>> >> >>> >> >> > <zturner at google.com>
>>>>>> >> >>> >> >> > wrote:
>>>>>> >> >>> >> >> >>
>>>>>> >> >>> >> >> >> On Thu, Feb 1, 2018 at 10:48 AM Hans Wennborg via
>>>>>> Phabricator
>>>>>> >> >>> >> >> >> <reviews at reviews.llvm.org> wrote:
>>>>>> >> >>> >> >> >>>
>>>>>> >> >>> >> >> >>> hans added inline comments.
>>>>>> >> >>> >> >> >>>
>>>>>> >> >>> >> >> >>>
>>>>>> >> >>> >> >> >>> ================
>>>>>> >> >>> >> >> >>> Comment at: llvm/tools/msbuild/Clang.Cpp.C
>>>>>> ommon.props:41
>>>>>> >> >>> >> >> >>> +
>>>>>> >> >>> >> >> >>> +    <!-- The registry key may not be set if it's an
>>>>>> old
>>>>>> >> >>> >> >> >>> installer,
>>>>>> >> >>> >> >> >>> try
>>>>>> >> >>> >> >> >>> the newest version that exists -->
>>>>>> >> >>> >> >> >>> +    <LLVMVersion Condition="'$(LLVMVersion)' == ''
>>>>>> and
>>>>>> >> >>> >> >> >>>
>>>>>> >> >>> >> >> >>>
>>>>>> >> >>> >> >> >>> Exists('$(LLVMInstallDir)\lib\
>>>>>> clang\7.0.0')">7.0.0</LLVMVersion>
>>>>>> >> >>> >> >> >>> ----------------
>>>>>> >> >>> >> >> >>> zturner wrote:
>>>>>> >> >>> >> >> >>> > hans wrote:
>>>>>> >> >>> >> >> >>> > > As I mentioned before, separating the toolset
>>>>>> config
>>>>>> >> >>> >> >> >>> > > from
>>>>>> >> >>> >> >> >>> > > the
>>>>>> >> >>> >> >> >>> > > actual
>>>>>> >> >>> >> >> >>> > > toolchain installation makes me a little nervous.
>>>>>> >> >>> >> >> >>> > >
>>>>>> >> >>> >> >> >>> > > But if we're doing it, the version checks below
>>>>>> should
>>>>>> >> >>> >> >> >>> > > probably
>>>>>> >> >>> >> >> >>> > > include the .1 versions too, i.e. at least 5.0.1
>>>>>> and
>>>>>> >> >>> >> >> >>> > > 6.0.1.
>>>>>> >> >>> >> >> >>> > Unless we're going to release the full thing
>>>>>> including the
>>>>>> >> >>> >> >> >>> > compiler,
>>>>>> >> >>> >> >> >>> > linker, etc through the marketplace I don't see an
>>>>>> >> >>> >> >> >>> > alternative.
>>>>>> >> >>> >> >> >>> > In
>>>>>> >> >>> >> >> >>> > any
>>>>>> >> >>> >> >> >>> > case, I actually think this it's preferable this
>>>>>> way.
>>>>>> >> >>> >> >> >>> > There's
>>>>>> >> >>> >> >> >>> > nothing
>>>>>> >> >>> >> >> >>> > really about the two that benefits from having them
>>>>>> >> >>> >> >> >>> > coupled
>>>>>> >> >>> >> >> >>> > together, as far
>>>>>> >> >>> >> >> >>> > as I can see.   I'm willing to be convinced
>>>>>> though, if we
>>>>>> >> >>> >> >> >>> > can
>>>>>> >> >>> >> >> >>> > figure
>>>>>> >> >>> >> >> >>> > out how
>>>>>> >> >>> >> >> >>> > to to do it so that we can still ship it on the
>>>>>> >> >>> >> >> >>> > marketplace.
>>>>>> >> >>> >> >> >>> "There's nothing really about the two that benefits
>>>>>> from
>>>>>> >> >>> >> >> >>> having
>>>>>> >> >>> >> >> >>> them
>>>>>> >> >>> >> >> >>> coupled together,"
>>>>>> >> >>> >> >> >>>
>>>>>> >> >>> >> >> >>> The toolset needs to know at least where to find the
>>>>>> >> >>> >> >> >>> toolchain
>>>>>> >> >>> >> >> >>> and
>>>>>> >> >>> >> >> >>> how
>>>>>> >> >>> >> >> >>> to
>>>>>> >> >>> >> >> >>> invoke it. If we decouple them, there needs to be an
>>>>>> >> >>> >> >> >>> interface
>>>>>> >> >>> >> >> >>> between
>>>>>> >> >>> >> >> >>> them
>>>>>> >> >>> >> >> >>> that can't change: in this case the LLVM path and
>>>>>> version
>>>>>> >> >>> >> >> >>> number in
>>>>>> >> >>> >> >> >>> the
>>>>>> >> >>> >> >> >>> registry.
>>>>>> >> >>> >> >> >>
>>>>>> >> >>> >> >> >> Has that ever changed?  Doesn’t seem too onerous,
>>>>>> using the
>>>>>> >> >>> >> >> >> registry
>>>>>> >> >>> >> >> >> is
>>>>>> >> >>> >> >> >> the windows way anyway, if anything this feels like
>>>>>> the
>>>>>> >> >>> >> >> >> proper
>>>>>> >> >>> >> >> >> way.
>>>>>> >> >>> >> >> >>
>>>>>> >> >>> >> >> >>
>>>>>> >> >>> >> >> >>>
>>>>>> >> >>> >> >> >>>
>>>>>> >> >>> >> >> >>> But at the same time you're baking in all this logic
>>>>>> in the
>>>>>> >> >>> >> >> >>> toolset
>>>>>> >> >>> >> >> >>> about
>>>>>> >> >>> >> >> >>> how to invoke the toolchain, what flags are
>>>>>> supported, etc.
>>>>>> >> >>> >> >> >>> Those
>>>>>> >> >>> >> >> >>> things are
>>>>>> >> >>> >> >> >>> strongly dependent on the toolchain, which in this
>>>>>> >> >>> >> >> >>> de-coupled
>>>>>> >> >>> >> >> >>> world
>>>>>> >> >>> >> >> >>> seems
>>>>>> >> >>> >> >> >>> problematic. It seems like you're actually making the
>>>>>> >> >>> >> >> >>> coupling
>>>>>> >> >>> >> >> >>> tighter
>>>>>> >> >>> >> >> >>> in
>>>>>> >> >>> >> >> >>> that way, except you still want to ship the two parts
>>>>>> >> >>> >> >> >>> separately.
>>>>>> >> >>> >> >> >>>
>>>>>> >> >>> >> >> >>> Are there restrictions in the marketplace about how
>>>>>> big a
>>>>>> >> >>> >> >> >>> vsix
>>>>>> >> >>> >> >> >>> can
>>>>>> >> >>> >> >> >>> be?
>>>>>> >> >>> >> >> >>> Because if not, I think we could just package up
>>>>>> >> >>> >> >> >>> clang+headers+runtime
>>>>>> >> >>> >> >> >>> into
>>>>>> >> >>> >> >> >>> a vsix and ship the whole thing, and maybe that
>>>>>> would be the
>>>>>> >> >>> >> >> >>> best
>>>>>> >> >>> >> >> >>> thing.
>>>>>> >> >>> >> >> >>
>>>>>> >> >>> >> >> >> An installer is very large though, and even if it’s
>>>>>> allowed
>>>>>> >> >>> >> >> >> it’s
>>>>>> >> >>> >> >> >> kind
>>>>>> >> >>> >> >> >> of
>>>>>> >> >>> >> >> >> obnoxious to have to download a large amount of stuff
>>>>>> if only
>>>>>> >> >>> >> >> >> one
>>>>>> >> >>> >> >> >> thing
>>>>>> >> >>> >> >> >> changes.  Being able to push changes to the
>>>>>> Integration
>>>>>> >> >>> >> >> >> independently
>>>>>> >> >>> >> >> >> of an
>>>>>> >> >>> >> >> >> llvm release seems like a feature to me.
>>>>>> >> >>> >> >> >>
>>>>>> >> >>> >> >> >>  coupling it would also make it more difficult to use
>>>>>> a
>>>>>> >> >>> >> >> >> custom
>>>>>> >> >>> >> >> >> built
>>>>>> >> >>> >> >> >> llvm
>>>>>> >> >>> >> >> >> toolchain, i can just change a registry setting right
>>>>>> now and
>>>>>> >> >>> >> >> >> it’s
>>>>>> >> >>> >> >> >> good
>>>>>> >> >>> >> >> >> to
>>>>>> >> >>> >> >> >> go.  Even the builtin VS toolchains use the registry
>>>>>> to
>>>>>> >> >>> >> >> >> locate
>>>>>> >> >>> >> >> >> paths,
>>>>>> >> >>> >> >> >> and we
>>>>>> >> >>> >> >> >> were already reading the registry before this anyway
>>>>>> >> >>> >> >> >>
>>>>>> >> >>> >> >> >>
>>>>>> >> >>> >> >> >>>
>>>>>> >> >>> >> >> >>>
>>>>>> >> >>> >> >> >>> Or we could just stick to the current installer
>>>>>> version and
>>>>>> >> >>> >> >> >>> make it
>>>>>> >> >>> >> >> >>> a
>>>>>> >> >>> >> >> >>> little smarter about finding VS2017. Maybe instead
>>>>>> of the
>>>>>> >> >>> >> >> >>> batch
>>>>>> >> >>> >> >> >>> files
>>>>>> >> >>> >> >> >>> we
>>>>>> >> >>> >> >> >>> write an actual program that finds the installation
>>>>>> and
>>>>>> >> >>> >> >> >>> copies
>>>>>> >> >>> >> >> >>> the
>>>>>> >> >>> >> >> >>> files.
>>>>>> >> >>> >> >> >>
>>>>>> >> >>> >> >> >> I definitely think vsix is the way to go.  I’d hate
>>>>>> to stick
>>>>>> >> >>> >> >> >> with
>>>>>> >> >>> >> >> >> batch
>>>>>> >> >>> >> >> >> files and not use the proper method of having an
>>>>>> extension.
>>>>>> >> >>> >> >> >> It’s
>>>>>> >> >>> >> >> >> also
>>>>>> >> >>> >> >> >> more
>>>>>> >> >>> >> >> >> discoverable as an extension on the marketplace.
>>>>>> >> >>> >> >> >>
>>>>>> >> >>> >> >> >>
>>>>>> >> >>> >> >> >>>
>>>>>> >> >>> >> >> >>>
>>>>>> >> >>> >> >> >>>
>>>>>> >> >>> >> >> >>> ================
>>>>>> >> >>> >> >> >>> Comment at: llvm/tools/msbuild/LLVM.props:8
>>>>>> >> >>> >> >> >>> +    <!-- Friendly names added to the
>>>>>> PlatformToolset in the
>>>>>> >> >>> >> >> >>> property
>>>>>> >> >>> >> >> >>> pages. -->
>>>>>> >> >>> >> >> >>> +    <_PlatformToolsetFriendlyNameFor_llvm
>>>>>> >> >>> >> >> >>> Condition="'$(_PlatformToolsetFriendlyNameFor_llvm)'
>>>>>> ==
>>>>>> >> >>> >> >> >>> ''">Clang
>>>>>> >> >>> >> >> >>> for
>>>>>> >> >>> >> >> >>> Windows</_PlatformToolsetFriendlyNameFor_llvm>
>>>>>> >> >>> >> >> >>> +  </PropertyGroup>
>>>>>> >> >>> >> >> >>> ----------------
>>>>>> >> >>> >> >> >>> zturner wrote:
>>>>>> >> >>> >> >> >>> > hans wrote:
>>>>>> >> >>> >> >> >>> > > Hmm, we previously intentionally called the
>>>>>> toolset
>>>>>> >> >>> >> >> >>> > > "LLVM"
>>>>>> >> >>> >> >> >>> > > with
>>>>>> >> >>> >> >> >>> > > the
>>>>>> >> >>> >> >> >>> > > thinking that it would eventually include lld and
>>>>>> >> >>> >> >> >>> > > designated
>>>>>> >> >>> >> >> >>> > > the
>>>>>> >> >>> >> >> >>> > > complete
>>>>>> >> >>> >> >> >>> > > llvm toolchain, not just Clang. And is the "for
>>>>>> Windows"
>>>>>> >> >>> >> >> >>> > > part
>>>>>> >> >>> >> >> >>> > > necessary?
>>>>>> >> >>> >> >> >>> > Do you think there's any value in having a toolset
>>>>>> that
>>>>>> >> >>> >> >> >>> > does
>>>>>> >> >>> >> >> >>> > Clang+Link
>>>>>> >> >>> >> >> >>> > and a second one that does Clang+LLD?  Or do you
>>>>>> think we
>>>>>> >> >>> >> >> >>> > should
>>>>>> >> >>> >> >> >>> > stick with
>>>>>> >> >>> >> >> >>> > only a single one?  I can change the name to LLVM
>>>>>> though.
>>>>>> >> >>> >> >> >>> The best would be to only have one, but where the
>>>>>> user could
>>>>>> >> >>> >> >> >>> select
>>>>>> >> >>> >> >> >>> between the two linkers, I think.
>>>>>> >> >>> >> >> >>
>>>>>> >> >>> >> >> >> Yea.  Can try that in a followup, may be tricky though
>>>>>> >> >>> >> >> >>
>>>>>> >> >>> >> >> >>>
>>>>>> >> >>> >> >> >>>
>>>>>> >> >>> >> >> >>>
>>>>>> >> >>> >> >> >>> ================
>>>>>> >> >>> >> >> >>> Comment at: llvm/tools/msbuild/Toolset.targets:38
>>>>>> >> >>> >> >> >>> +
>>>>>> >> >>> >> >> >>> +    <!-- Warn if Fiber Safe Optimizations are
>>>>>> enabled, and
>>>>>> >> >>> >> >> >>> then
>>>>>> >> >>> >> >> >>> ignore
>>>>>> >> >>> >> >> >>> them. -->
>>>>>> >> >>> >> >> >>> +    <Warning
>>>>>> >> >>> >> >> >>> Condition="'%(ClCompile.Enable
>>>>>> FiberSafeOptimizations)'
>>>>>> >> >>> >> >> >>> ==
>>>>>> >> >>> >> >> >>> 'true'"
>>>>>> >> >>> >> >> >>> ----------------
>>>>>> >> >>> >> >> >>> zturner wrote:
>>>>>> >> >>> >> >> >>> > hans wrote:
>>>>>> >> >>> >> >> >>> > > This seems to duplicate a lot of logic from
>>>>>> clang-cl.
>>>>>> >> >>> >> >> >>> > > It's
>>>>>> >> >>> >> >> >>> > > nice
>>>>>> >> >>> >> >> >>> > > to
>>>>>> >> >>> >> >> >>> > > provide a good UI for the user, but maintaining
>>>>>> this
>>>>>> >> >>> >> >> >>> > > seems
>>>>>> >> >>> >> >> >>> > > a
>>>>>> >> >>> >> >> >>> > > lot
>>>>>> >> >>> >> >> >>> > > of work.
>>>>>> >> >>> >> >> >>> > > Are you not concerned that this will rot?
>>>>>> >> >>> >> >> >>> > I don't think it will.  Maybe I'm being overly
>>>>>> optimistic
>>>>>> >> >>> >> >> >>> > here,
>>>>>> >> >>> >> >> >>> > but
>>>>>> >> >>> >> >> >>> > the
>>>>>> >> >>> >> >> >>> > only case we would ever need to maintain this
>>>>>> again is if
>>>>>> >> >>> >> >> >>> > we
>>>>>> >> >>> >> >> >>> > started
>>>>>> >> >>> >> >> >>> > supporting these options.  Fiber Safe
>>>>>> Optimizations, for
>>>>>> >> >>> >> >> >>> > example,
>>>>>> >> >>> >> >> >>> > I'm pretty
>>>>>> >> >>> >> >> >>> > sure we will never support.  If MSVC ever removes
>>>>>> the
>>>>>> >> >>> >> >> >>> > option,
>>>>>> >> >>> >> >> >>> > for
>>>>>> >> >>> >> >> >>> > example,
>>>>>> >> >>> >> >> >>> > we can do nothing and continue to work.
>>>>>> >> >>> >> >> >>> >
>>>>>> >> >>> >> >> >>> > We could also just silently ignore them and just
>>>>>> pass the
>>>>>> >> >>> >> >> >>> > option
>>>>>> >> >>> >> >> >>> > through to clang-cl, but these are pretty unusual
>>>>>> options
>>>>>> >> >>> >> >> >>> > with
>>>>>> >> >>> >> >> >>> > pretty
>>>>>> >> >>> >> >> >>> > specialized use cases, so I feel like if I had
>>>>>> gone out of
>>>>>> >> >>> >> >> >>> > my
>>>>>> >> >>> >> >> >>> > way
>>>>>> >> >>> >> >> >>> > to
>>>>>> >> >>> >> >> >>> > enable
>>>>>> >> >>> >> >> >>> > such a strange option I would want to know if the
>>>>>> compiler
>>>>>> >> >>> >> >> >>> > was
>>>>>> >> >>> >> >> >>> > not
>>>>>> >> >>> >> >> >>> > going to
>>>>>> >> >>> >> >> >>> > respect it.
>>>>>> >> >>> >> >> >>> I feel pretty strongly that we should handle this
>>>>>> clang-cl
>>>>>> >> >>> >> >> >>> side. If
>>>>>> >> >>> >> >> >>> a
>>>>>> >> >>> >> >> >>> flag is not supported, either we should ignore it,
>>>>>> or if
>>>>>> >> >>> >> >> >>> it's
>>>>>> >> >>> >> >> >>> something the
>>>>>> >> >>> >> >> >>> user would want to know about us not supporting, we
>>>>>> should
>>>>>> >> >>> >> >> >>> warn.
>>>>>> >> >>> >> >> >>> That's what
>>>>>> >> >>> >> >> >>> clang-cl tries to do currently, and if there are
>>>>>> flags we
>>>>>> >> >>> >> >> >>> don't
>>>>>> >> >>> >> >> >>> get
>>>>>> >> >>> >> >> >>> right,
>>>>>> >> >>> >> >> >>> we should fix it.
>>>>>> >> >>> >> >> >>>
>>>>>> >> >>> >> >> >>> And we do move flags from the unsupported to
>>>>>> supported
>>>>>> >> >>> >> >> >>> category
>>>>>> >> >>> >> >> >>> now
>>>>>> >> >>> >> >> >>> and
>>>>>> >> >>> >> >> >>> then, so the "only case we would ever need to
>>>>>> maintain this
>>>>>> >> >>> >> >> >>> again
>>>>>> >> >>> >> >> >>> is
>>>>>> >> >>> >> >> >>> if we
>>>>>> >> >>> >> >> >>> started supporting these options" scenario is real.
>>>>>> >> >>> >> >> >>
>>>>>> >> >>> >> >> >> It’s not a matter of clang-cl doing it right or
>>>>>> wrong, it’s
>>>>>> >> >>> >> >> >> that
>>>>>> >> >>> >> >> >> there
>>>>>> >> >>> >> >> >> are
>>>>>> >> >>> >> >> >> other moving parts before it even gets to clang-cl.
>>>>>> >> >>> >> >> >> Specifically,
>>>>>> >> >>> >> >> >> MSBuild.
>>>>>> >> >>> >> >> >> We’ve already seen one example of how  just letting
>>>>>> clang-cl
>>>>>> >> >>> >> >> >> do
>>>>>> >> >>> >> >> >> its
>>>>>> >> >>> >> >> >> thing is
>>>>>> >> >>> >> >> >> insufficient, and nothing we can ever do in clang-cl
>>>>>> can fix
>>>>>> >> >>> >> >> >> that.
>>>>>> >> >>> >> >> >> Given
>>>>>> >> >>> >> >> >> that it’s required sometimes, and that doing it for
>>>>>> all
>>>>>> >> >>> >> >> >> options
>>>>>> >> >>> >> >> >> doesn’t
>>>>>> >> >>> >> >> >> increase our maintenance burden, i think it makes
>>>>>> sense to do
>>>>>> >> >>> >> >> >> it
>>>>>> >> >>> >> >> >> everywhere
>>>>>> >> >>> >> >> >> and never have to deal with msbuild issues again.
>>>>>> >> >>> >> >> >>
>>>>>> >> >>> >> >> >>
>>>>>> >> >>> >> >> >>>
>>>>>> >> >>> >> >> >>>
>>>>>> >> >>> >> >> >>>
>>>>>> >> >>> >> >> >>> ================
>>>>>> >> >>> >> >> >>> Comment at: llvm/tools/msbuild/Toolset.targets:46
>>>>>> >> >>> >> >> >>> +             File="@(ClCompile)(0,0)"
>>>>>> >> >>> >> >> >>> +             Text="clang-cl does not support MSVC
>>>>>> Link Time
>>>>>> >> >>> >> >> >>> Optimization.  Disable this option in compatibility
>>>>>> settings
>>>>>> >> >>> >> >> >>> to
>>>>>> >> >>> >> >> >>> silence this
>>>>>> >> >>> >> >> >>> warning."/>
>>>>>> >> >>> >> >> >>> +
>>>>>> >> >>> >> >> >>> ----------------
>>>>>> >> >>> >> >> >>> zturner wrote:
>>>>>> >> >>> >> >> >>> > hans wrote:
>>>>>> >> >>> >> >> >>> > > But maybe we want clang-cl to map this to -flto
>>>>>> one day.
>>>>>> >> >>> >> >> >>> > > Now we
>>>>>> >> >>> >> >> >>> > > need
>>>>>> >> >>> >> >> >>> > > to update two places. And with the
>>>>>> toolset/toolchain
>>>>>> >> >>> >> >> >>> > > install
>>>>>> >> >>> >> >> >>> > > split, the two
>>>>>> >> >>> >> >> >>> > > places may be installed separately :-/
>>>>>> >> >>> >> >> >>> > That's even better then.  All we have to do is
>>>>>> change this
>>>>>> >> >>> >> >> >>> > xml,
>>>>>> >> >>> >> >> >>> > push
>>>>>> >> >>> >> >> >>> > a
>>>>>> >> >>> >> >> >>> > new build to the market place, and the VS UI will
>>>>>> update
>>>>>> >> >>> >> >> >>> > their
>>>>>> >> >>> >> >> >>> > extension for
>>>>>> >> >>> >> >> >>> > them.
>>>>>> >> >>> >> >> >>> >
>>>>>> >> >>> >> >> >>> > Note that we could do the mapping at the MSBuild
>>>>>> level, in
>>>>>> >> >>> >> >> >>> > this
>>>>>> >> >>> >> >> >>> > file
>>>>>> >> >>> >> >> >>> > down below where we have an `ItemGroup`.  Just add
>>>>>> a line
>>>>>> >> >>> >> >> >>> > that
>>>>>> >> >>> >> >> >>> > says
>>>>>> >> >>> >> >> >>> > `<AdditionalOptions
>>>>>> >> >>> >> >> >>> > Condition="%(ClCompile.WholeProgramOptimization)'
>>>>>> ==
>>>>>> >> >>> >> >> >>> > 'true'>-flto=thin
>>>>>> >> >>> >> >> >>> > %(AdditionalOptions)</AdditionalOptions>`
>>>>>> >> >>> >> >> >>> >
>>>>>> >> >>> >> >> >>> > and we can do this without touching clang.
>>>>>> >> >>> >> >> >>> But the toolset is decoupled from the toolchain in
>>>>>> your
>>>>>> >> >>> >> >> >>> proposal.
>>>>>> >> >>> >> >> >>>
>>>>>> >> >>> >> >> >>> Not only would we need to update both clang-cl and
>>>>>> this
>>>>>> >> >>> >> >> >>> file,
>>>>>> >> >>> >> >> >>> but
>>>>>> >> >>> >> >> >>> this
>>>>>> >> >>> >> >> >>> file would need to handle clang-cl versions both
>>>>>> before and
>>>>>> >> >>> >> >> >>> after.
>>>>>> >> >>> >> >> >>
>>>>>> >> >>> >> >> >> We wouldn’t have to update clang-cl.  We could map
>>>>>> ltcg to
>>>>>> >> >>> >> >> >> -flto=thin
>>>>>> >> >>> >> >> >> in
>>>>>> >> >>> >> >> >> the extension and it would automatically work with the
>>>>>> >> >>> >> >> >> installed
>>>>>> >> >>> >> >> >> toolchain.
>>>>>> >> >>> >> >> >>
>>>>>> >> >>> >> >> >>
>>>>>> >> >>> >> >> >>>
>>>>>> >> >>> >> >> >>>
>>>>>> >> >>> >> >> >>>
>>>>>> >> >>> >> >> >>> ================
>>>>>> >> >>> >> >> >>> Comment at: llvm/tools/msbuild/Toolset.targets:83
>>>>>> >> >>> >> >> >>> +
>>>>>> >> >>> >> >> >>> +    <!-- Warn if XML Documentation is generated,
>>>>>> and then
>>>>>> >> >>> >> >> >>> ignore
>>>>>> >> >>> >> >> >>> it.
>>>>>> >> >>> >> >> >>> -->
>>>>>> >> >>> >> >> >>> +    <Warning
>>>>>> >> >>> >> >> >>> Condition="'%(ClCompile.Genera
>>>>>> teXMLDocumentationFiles)'
>>>>>> >> >>> >> >> >>> ==
>>>>>> >> >>> >> >> >>> 'true'"
>>>>>> >> >>> >> >> >>> ----------------
>>>>>> >> >>> >> >> >>> zturner wrote:
>>>>>> >> >>> >> >> >>> > hans wrote:
>>>>>> >> >>> >> >> >>> > > Keeping up with all these flags seems like a
>>>>>> huge amount
>>>>>> >> >>> >> >> >>> > > of
>>>>>> >> >>> >> >> >>> > > work.
>>>>>> >> >>> >> >> >>> > > Why
>>>>>> >> >>> >> >> >>> > > not just let clang-cl ignore it?
>>>>>> >> >>> >> >> >>> > See the large comment at the top of the file.  For
>>>>>> some
>>>>>> >> >>> >> >> >>> > options,
>>>>>> >> >>> >> >> >>> > we
>>>>>> >> >>> >> >> >>> > could probably get by with this.  Maybe even this
>>>>>> one, I
>>>>>> >> >>> >> >> >>> > debated
>>>>>> >> >>> >> >> >>> > on
>>>>>> >> >>> >> >> >>> > this
>>>>>> >> >>> >> >> >>> > particular one.
>>>>>> >> >>> >> >> >>> >
>>>>>> >> >>> >> >> >>> > My bar was "If the option fundamentally changes
>>>>>> >> >>> >> >> >>> > assumptions
>>>>>> >> >>> >> >> >>> > about
>>>>>> >> >>> >> >> >>> > the
>>>>>> >> >>> >> >> >>> > way code could be compiled, we should generate an
>>>>>> error.
>>>>>> >> >>> >> >> >>> > If
>>>>>> >> >>> >> >> >>> > it
>>>>>> >> >>> >> >> >>> > changes the
>>>>>> >> >>> >> >> >>> > behavior of the language in a way we don't support,
>>>>>> >> >>> >> >> >>> > changes
>>>>>> >> >>> >> >> >>> > the
>>>>>> >> >>> >> >> >>> > way
>>>>>> >> >>> >> >> >>> > we
>>>>>> >> >>> >> >> >>> > generate code in a meaningful way, or causes
>>>>>> specialized
>>>>>> >> >>> >> >> >>> > output
>>>>>> >> >>> >> >> >>> > files to be
>>>>>> >> >>> >> >> >>> > written, warn, and if it's an option we ignore
>>>>>> then drop
>>>>>> >> >>> >> >> >>> > it"
>>>>>> >> >>> >> >> >>> >
>>>>>> >> >>> >> >> >>> > The last category there we could probably just pass
>>>>>> >> >>> >> >> >>> > through
>>>>>> >> >>> >> >> >>> > in
>>>>>> >> >>> >> >> >>> > some
>>>>>> >> >>> >> >> >>> > cases, but in that comment I also mentioned a case
>>>>>> where
>>>>>> >> >>> >> >> >>> > setting
>>>>>> >> >>> >> >> >>> > an
>>>>>> >> >>> >> >> >>> > option
>>>>>> >> >>> >> >> >>> > that clang-cl ignores impacts MSBuild's ability to
>>>>>> figure
>>>>>> >> >>> >> >> >>> > out
>>>>>> >> >>> >> >> >>> > dependencies
>>>>>> >> >>> >> >> >>> > and ends up causing a full rebuild every time even
>>>>>> when
>>>>>> >> >>> >> >> >>> > nothing
>>>>>> >> >>> >> >> >>> > changed.
>>>>>> >> >>> >> >> >>> >
>>>>>> >> >>> >> >> >>> > We can scour the entire cl build tasks and try to
>>>>>> discover
>>>>>> >> >>> >> >> >>> > if
>>>>>> >> >>> >> >> >>> > any
>>>>>> >> >>> >> >> >>> > other
>>>>>> >> >>> >> >> >>> > ones have unintended consequences, but I think
>>>>>> it's easier
>>>>>> >> >>> >> >> >>> > to
>>>>>> >> >>> >> >> >>> > just
>>>>>> >> >>> >> >> >>> > turn them
>>>>>> >> >>> >> >> >>> > off at the MSBuild level.  And as a side benefit,
>>>>>> the user
>>>>>> >> >>> >> >> >>> > gets
>>>>>> >> >>> >> >> >>> > shorter
>>>>>> >> >>> >> >> >>> > command lines, which is always nice.
>>>>>> >> >>> >> >> >>> >
>>>>>> >> >>> >> >> >>> > As for maintenance, this all looks like
>>>>>> zero-maintenance
>>>>>> >> >>> >> >> >>> > code
>>>>>> >> >>> >> >> >>> > to
>>>>>> >> >>> >> >> >>> > me.
>>>>>> >> >>> >> >> >>> > Did you have an example in mind of where we'd need
>>>>>> to
>>>>>> >> >>> >> >> >>> > update
>>>>>> >> >>> >> >> >>> > this?
>>>>>> >> >>> >> >> >>> > Whether
>>>>>> >> >>> >> >> >>> > it be a new VS version, or VS dropping support for
>>>>>> one of
>>>>>> >> >>> >> >> >>> > these
>>>>>> >> >>> >> >> >>> > options or
>>>>>> >> >>> >> >> >>> > deprecating them, I don't think we'd have to do
>>>>>> anything.
>>>>>> >> >>> >> >> >>> The maintenance would come from when clang-cl
>>>>>> changes how it
>>>>>> >> >>> >> >> >>> handles
>>>>>> >> >>> >> >> >>> some
>>>>>> >> >>> >> >> >>> option, or when VS adds new options.
>>>>>> >> >>> >> >> >>
>>>>>> >> >>> >> >> >> But these are all really obscure options that we will
>>>>>> >> >>> >> >> >> probably
>>>>>> >> >>> >> >> >> never
>>>>>> >> >>> >> >> >> touch.  When vc adds new options we’re not obligated
>>>>>> to
>>>>>> >> >>> >> >> >> update
>>>>>> >> >>> >> >> >> this
>>>>>> >> >>> >> >> >> file
>>>>>> >> >>> >> >> >> either.
>>>>>> >> >>> >> >> >>
>>>>>> >> >>> >> >> >>
>>>>>> >> >>> >> >> >>>
>>>>>> >> >>> >> >> >>>
>>>>>> >> >>> >> >> >>>
>>>>>> >> >>> >> >> >>> ================
>>>>>> >> >>> >> >> >>> Comment at: llvm/tools/msbuild/install.bat:10
>>>>>> >> >>> >> >> >>> +REM Older versions of VS would look for these files
>>>>>> in the
>>>>>> >> >>> >> >> >>> Program
>>>>>> >> >>> >> >> >>> Files\MSBuild directory
>>>>>> >> >>> >> >> >>> +REM but with VS2017 it seems to look for these
>>>>>> directly in
>>>>>> >> >>> >> >> >>> the
>>>>>> >> >>> >> >> >>> Visual
>>>>>> >> >>> >> >> >>> Studio instance.
>>>>>> >> >>> >> >> >>> +REM This means we'll need to do a little extra work
>>>>>> to
>>>>>> >> >>> >> >> >>> properly
>>>>>> >> >>> >> >> >>> detect
>>>>>> >> >>> >> >> >>> all the various
>>>>>> >> >>> >> >> >>> ----------------
>>>>>> >> >>> >> >> >>> zturner wrote:
>>>>>> >> >>> >> >> >>> > hans wrote:
>>>>>> >> >>> >> >> >>> > > Don't we want to support at least 2015 too?
>>>>>> >> >>> >> >> >>> > Mentioned in the other review, but the install.bat
>>>>>> file
>>>>>> >> >>> >> >> >>> > shouldn't
>>>>>> >> >>> >> >> >>> > really be used anymore except for during
>>>>>> development.  The
>>>>>> >> >>> >> >> >>> > VSIX
>>>>>> >> >>> >> >> >>> > supports
>>>>>> >> >>> >> >> >>> > both 2015 and 2017 (I tested it in both and
>>>>>> confirmed it
>>>>>> >> >>> >> >> >>> > works)
>>>>>> >> >>> >> >> >>> Hmm, but then we should delete it, or at least take
>>>>>> it out
>>>>>> >> >>> >> >> >>> of
>>>>>> >> >>> >> >> >>> the
>>>>>> >> >>> >> >> >>> installer, and we need a replacement. As it is now,
>>>>>> if we
>>>>>> >> >>> >> >> >>> land
>>>>>> >> >>> >> >> >>> this,
>>>>>> >> >>> >> >> >>> it
>>>>>> >> >>> >> >> >>> breaks the installer for versions before 2017.
>>>>>> >> >>> >> >> >>
>>>>>> >> >>> >> >> >>
>>>>>> >> >>> >> >> >> I thought i took it out of the installer, but maybe I
>>>>>> missed
>>>>>> >> >>> >> >> >> something.
>>>>>> >> >>> >> >> >> We still need it for dev purposes because it allows
>>>>>> us to
>>>>>> >> >>> >> >> >> overwrite
>>>>>> >> >>> >> >> >> the
>>>>>> >> >>> >> >> >> existing installed version with new files
>>>>>> >> >>> >> >> >
>>>>>> >> >>> >> >> >
>>>>>> >> >>> >> >> > _______________________________________________
>>>>>> >> >>> >> >> > llvm-commits mailing list
>>>>>> >> >>> >> >> > llvm-commits at lists.llvm.org
>>>>>> >> >>> >> >> > http://lists.llvm.org/cgi-bin/
>>>>>> mailman/listinfo/llvm-commits
>>>>>> >> >>> >> >> >
>>>>>>
>>>>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20180202/d49dab1c/attachment.html>