[swift-corelibs-dev] Building Foundation with SwiftPM

[Ankit Aggarwal]

On Tue, Jan 31, 2017 at 8:13 AM, Philippe Hausler via swift-corelibs-dev <
swift-corelibs-dev at swift.org> wrote:

> So there are a few issues that would be a bit tricky to deal with:
>
> SwiftPM uses Foundation so you would have to devise some way to build
> SwiftPM either without Foundation (which seems sub-optimal or replication
> of effort/code), directly importing parts of Foundation into the code-base
> for SwiftPM which might result in a synchronization issue of code, or a
> last-build result re-build of Foundation used in SwiftPM which seems like a
> pain when it comes to first time setup.
>
> Foundation’s build environment is a bit tricky since it is not just plain
> C, we have assembly and some really funky linker tricks that might pose an
> issue. Also it might be a bit difficult to build CoreFoundation as it’s own
> target (as it stands now you can technically build CF without swift and use
> that independently on Linux - which elides the need to publish a separate
> CFLite).
>

Note that you can have C and Swift targets in SwiftPM (and also statically
link them) but I guess it will be difficult to get around the assembly and
linker tricks. We do allow passing arbitrary compiler flags during
invocation which are a workaround until we have a build settings story.

>From previous build infrastructure efforts that I have undertaken; the
> general consensus is that using SwiftPM would be nice but it doesn’t offer
> enough of a compelling reason to switch and complicate the rest of the
> Swift build process (which is already very complex).
>
>
Daniel mentioned that we could add support for building Foundation with
SwiftPM but not do it in the overall Swift build process, which I think
makes sense and might be a nice thing for beginners. It is also very
convenient for regular development, for e.g. most of the time I use a trunk
snapshot from swift.org to develop SwiftPM. There are hardly any issues
esp. since Swift 3 and syntax stability. And of course there is Swift CI to
catch any issue before merging.


> Now the other alternative is that Foundation could be built with cmake.
> That has been something I have explored and it shows some promise. However
> as for fish to fry, it is a very small one.
>
> Now I think fixing the dirty file bits from the build script might be a
> good thing to fix even without changing the build infrastructure. I have
> tried to fix this problem a few times but it ends up getting really complex
> really quickly.
>
> If you want to dive into the current build system or perhaps look at cmake
> let me know if there are things that I can help out to clarify.
>
> P.S. what slack server are you discussing this on? I was un-aware of any
> slack servers setup for swift.
>
>
SwiftPM has an "unofficial" slack team, you can join here:
http://swift-package-manager.herokuapp.com
More info here:
https://lists.swift.org/pipermail/swift-build-dev/Week-of-Mon-20160530/000497.html


> On Jan 30, 2017, at 4:49 PM, Robert F Dickerson via swift-corelibs-dev <
> swift-corelibs-dev at swift.org> wrote:
>
> This has probably been discussed in the past, but wanted to revisit the
> idea of using native Swift tools to build Foundation. I brought this up in
> the Slack group, and it seemed to be warmly received- although probably
> still not simple because of some cyclical dependency issues in the build
> process.
>
> But, I think that there would be a lot of value in being able to build
> Foundation (and CoreFoundation) only using SwiftPM, in other words, simply
> with `swift build`.
>
> Now that SwiftPM is improving its ability to pass in compilation flags
> more easily and C module compilation. I think that the project could be
> restructured to make this work. What would be the obstacles for getting
> this working?
>
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