[swift-dev] Request for review on Windows CMake changes

[Saleem Abdulrasool]

On Sat, Dec 9, 2017 at 9:21 AM, David Zarzycki via swift-dev <
swift-dev at swift.org> wrote:

> Can somebody please also speak up to why Windows needs to remove the
> "-Wl,-z,defs” from CXX_FLAGS? At the very least, I’d like to see the
> project-wide removal of this useful flag limited to just the Windows builds.
>

Currently, the way that swift approaches building goes against the way that
CMake intended cross-compilation to work.  The result is that we end up
having to do a number of fairly nasty things to get things to work.
Options are not spelt the same way nor do all options make sense on all
targets.  `-z defs` is an ELF specific option.  However, because we use the
same rules for all targets using the build as the host, we cannot simply
filter based on the target.  Instead, this needs to be done at the lowest
possible layer when we know if the build is ELF or COFF or MachO.  That
said, I think that exporting this flag from LLVM is not the right thing and
that swift should be re-adding that flag if it so decides to use (which for
ELF targets, it really is a good idea).

I think that if we start splitting things up and using ExternalProject to
joining the various pieces we should be able to accommodate that and re-use
the cross-compilation support in CMake.  I think that there is some work
that has been done there for the SDK overlay and libdispatch.


>
> On Dec 8, 2017, at 20:36, Thomas Roughton via swift-dev <
> swift-dev at swift.org> wrote:
>
> Hi all,
>
> I've had a PR (https://github.com/apple/swift/pull/13140) that's been
> open for about 10 days with a few CMake changes to fix the Windows
> cross-compile build. I wasn't sure who best to ask to review it, but was
> suggested to post here with it.
>
> Could someone familiar with that area maybe add themselves as a reviewer
> and then later take a look when they get a chance (even if that's not for a
> few weeks)? There's no particular urgency, but it'd be ideal if possible to
> have the changes in before it needs to be rebased too many times.
>
> Thanks,
> Thomas
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-- 
Saleem Abdulrasool
compnerd (at) compnerd (dot) org
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