Foundation on Windows (CI/Nightlies)

I am currently using this build.
And I haven't had a problem with it yet.
I use a toolchain that was built on the same day.

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Patches to improve the documentation are more than welcome :-). As to the builds for Foundation being out of date, that is due to a build issue - I've not had time to look into it. Basically, Foundation requires CURL built with zlib, and the builds currently do not link against zlib resulting in unresolved symbols. I can probably put in a quick workaround for this, though, the best solution is to help move everything to CMake 3.15+.

FYI, the x64 build has been repaired. The ARM64 builds are still a problem due to a clang issue.

Thank you @Daniel_Mullenborn for the links.

I tried to mix the content of into the content of Before doing this, I got the error "no such module 'Foundation'". Now, it get the following error (first line says the file 'Foundation.lib' cannot be opened):

LINK : fatal error LNK1104: Datei "Foundation.lib" kann nicht geöffnet werden.
clang: error: linker command failed with exit code 1104 (use -v to see invocation)
:0: error: link command failed with exit code 1104 (use -v to see invocation)

So how do I add the contents of to the content of, i.e. how to I add Foundation and maybe other libraries to my already installed Swift toolchain?

By the way, what is the "windows-sdk.msi" installer doing, does it install Swift + Foundation, and does it add e.g. the file "module.modulemap" etc.? Should I use the installer instead?

@compnerd: The point for me is not that some builds go wrong, but that it would be nice to get the same successful builds (same version) for Swift, Foundation, and the Runtime easily even if they do not contain the very last changes.

Yup, it would be great to have a full toolchain installer or archive similar to the ones in Currently you have to download multiple ones a mix and match some artifacts.

@pvieito: To be fair, that should not be a critique to @compnerd, who is doing a great job; mixing those directories on a regular basis could be done by someone else (if this could not somehow be integrated into the process). Currently, I just would like to have a clear explanation of how to mix them (the obvious way I tried did not work, or I made some stupid mistakes).

Yeah, of course, we should be very thankful for the great job @compnerd has done!

Now that the port is very advanced I also think we should start asking about official Windows support (including proper GitHub PR CI support and official toolchains in to Swift Project Lead (ie. Apple and @tkremenek).


Thanks for that feedback. I was hoping that the Windows instructions would be sufficient for the explanation of what was going on. The split of the components is intentional as I believe that it provides better building blocks (the pieces are setup to be composed into a final image). The desired break down is as follows:

  • toolchain: the actual tools needed to compile C/C++/Swift code and inspect binaries (e.g. clang, swiftc, lld)
  • sdk: the Swift supplemental content needed to build software for a platform (e.g. Windows, Android, Linux)
  • developer tools: tools needed to write software (e.g. llbuild, s-p-m, SourceKit-LSP)

Currently, the last component is not available, but, I hope to add that to the builds (although some part of the build does exist currently).

You would need at least the first two items for writing Swift code.

The first item - toolchain - needs to be for the machine that you are going to be working on (currently, Windows x64 or Linux x64; Windows arm64 is experimental).

You additionally need the SDK for the platform you are building for (currently one of Windows, Android, or Linux). There is some discussion going on at Swift Linux layout considerations (aka Linux is difficult, lets go shopping) about how to deal with multiple architectures for these platforms. With the patch which led to that thread, it is possible to have these SDKs be relocatable wherever you like - you just pass along some flags to the compiler to identify where they are stored.

Finally, I suspect is the piece that most people claim is absolutely required: the developer tools. This is currently under development still and includes items for the developer not the final product. These are tied to the machine that you are building on again (just like the toolchain). It would include tools like s-p-m and SourceKit-LSP.

Why devtools is split out

The reason to split out the developer tools like this is two fold. First of all, these are high level tools which are written in Swift, and as such need the SDK to be prepared for the host, before they are usable (that is, we need the previous component for Windows before we can build these tools for Windows). Second of all, they are not part of the core toolchain, but really part of the IDE experience.

My long term vision (plan?) is to actually get the developer tools stable and then try to construct a single VSCode build which has the toolchain and devtools pre-packaged and configured. You would just add the SDK for the platform that you wish to target and can start developing :-). It should be possible to actually have a plugin in VSCode which would download the tools (much like how Xcode downloads the simulator images or Android Studio downloads pieces).

Each one of these layers is built upon the previous and it takes time to ensure that the base is solid enough to support that. I have been slowly moving through the strata building up the infrastructure to make that possible. In the mean time, I have been simultaneously trying to make all the pieces entirely relocatable, which makes it easier for others to actually experiment with the artifacts that are being published.

If the current documentation on the getting started workflow is not sufficient, I would love to have some patches to improve them and make them clearer for others. I am trying to find a way to lower the bar for others to use Swift on the platform of their choice (both for writing and running). If there are pieces which I have overlooked in the short term, I would be open to trying to smooth those out in a way that makes sense for the longer term.


Great outlook.

Please do not forget that the environment for running the resulting program should also be available in a compact, reduced form, or maybe this would be resolved with static linking (which is not available yet?)? I am talking here about running on a "naked" Windows (without any Visual Studio or additional Windows Runtime installed), i.e. it is should be easy to build a compact, small package that is runnable as-is (without installation) on a freshly installed Windows.

Right now you only need Visual C++ Redistributable for Visual Studio 2015 to run Swift on Windows.

@Daniel_Mullenborn: It seems to be OK (for Microsoft) to just put the needed DLLs (that are also contained in this "Visual C++ Redistributable") into the according directory of the application see But yes, you are right in principle, thanks. But what is still needed is in extraction of DLLs from Swift/Foundation or what else is needed, the whole Developer directory is just too much.

I think if you have these files in the folder it should work.


All together about 50MB.

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@Daniel_Mullenborn: Thanks.

All that ? is this what's needed to run the compiled .exe program ? seems to be a lot.. are there plans to shrink that, by a lot, on same level as rust or even c++ ?

The dependency to ICU may disappear sometime, but the rest will remain, which will be 30MB.

You should see my previous post about the split of the SDK content into the pure SDK content and the runtime content. In fact, right now, I am generating a MSI which installs just the DLLs that need to be redistributed.

@RUSshy - it already is at the same level of a C++ library - if you have a dependency on boost, you need to distribute that :slight_smile:. Take a look at - the runtime is ~5MiB.

I don't think that swiftDemangle and swiftRemoteMirror are absolutely required (unless you are using remote mirrors or you are programatically using the undeocration API).


For a more complex program, I also needed swiftDispatch.dll. I did not find swiftDemangle.dll and did not include swiftRemoteMirror.dll. For some strange reason I needed both icu*64 and icu*63. So my full list of DLLs is the following, it is tested on a "naked" Windows 10:

from C:\Library\Developer\Toolchains\unknown-Asserts-development.xctoolchain\usr\bin:


from C:\Library\Developer\Platforms\Windows.platform\Developer\SDKs\Windows.sdk\usr\bin:


from C:\Library\icu-63.1\bin:

icudt63.dll OK
icuin63.dll OK
icuio63.dll OK
icutu63.dll OK
icuuc63.dll OK

from C:\Library\icu-64.2\bin:

icudt64.dll OK
icuin64.dll OK
icuio64.dll OK
icutu64.dll OK
icuuc64.dll OK

from C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Redist\MSVC\14.16.27012\x64\Microsoft.VC141.CRT:


The reason for the two versions of ICU is due to the builds in use. I need to update the rules for the builds to all move to 64.1. You will need swiftDispatch.dll if you want to use Dispatch. swiftSwiftOnoneSupport.dll should not be needed by users - that is only needed when building with -Onone which is unlikely to be shipped. The CRT is supposed to be a separate product from Microsoft - the MSVC redistributable. The Foundation libraries are only needed if you are using Foundation.

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