Building Swift on Windows

Visual Studio 2017 or newer is needed to build swift on Windows.

1. Install dependencies

Install the latest version of Visual Studio
Make sure to include “Programming Languages|Visual C++” and “Windows and Web Development|Universal Windows App Development|Windows SDK” in your installation.

2. Clone the repositories

Configure git to work with Unix file endings
Create a folder to contain all the Swift repositories
Clone apple/swift-cmark into a folder named cmark
Clone apple/swift-clang into a folder named clang
Clone apple/swift-llvm into a folder named llvm
Clone apple/swift-compiler-rt into a folder named compiler-rt
Clone apple/swift into a folder named swift
Clone apple/swift-corelibs-libdispatch into a folder named swift-corelibs-libdispatch
Clone apple/swift-corelibs-foundation into a folder named swift-corelibs-foundation
Clone apple/swift-corelibs-xctest into a folder name swift-corelibs-xctest
Clone apple/swift-lldb into a folder named lldb
Clone apple/swift-llbuild into a folder named llbuild
Clone apple/swift-package-manager info a folder named swift-package-manager
Clone curl into a folder named curl
Clone libxml2 into a folder named libxml2

Currently, other repositories in the Swift project have not been tested and may not be supported.

This guide assumes your sources live at the root of S:. If your sources live elsewhere, you can create a substitution for this:

subst S: <path to sources>

S:
git clone https://github.com/apple/swift-cmark cmark
git clone https://github.com/apple/swift-clang clang
git clone https://github.com/apple/swift-llvm llvm
git clone https://github.com/apple/swift-compiler-rt compiler-rt
git clone -c core.autocrlf=input -c core.symlinks=true https://github.com/apple/swift
git clone https://github.com/apple/swift-corelibs-libdispatch
git clone https://github.com/apple/swift-corelibs-foundation
git clone https://github.com/apple/swift-corelibs-xctest
git clone https://github.com/apple/swift-lldb lldb
git clone https://github.com/apple/swift-llbuild llbuild
git clone -c core.autocrlf=input https://github.com/apple/swift-package-manager
git clone https://github.com/curl/curl.git
git clone https://gitlab.gnome.org/GNOME/libxml2.git

3. Acquire ICU

Download ICU from ICU Project for Windows x64 and extract the folder to a new folder called thirdparty. In other words, there should be a folder S:\thirdparty\icu4c-64_2-Win64-MSVC2017 with the ICU.
Add the bin64 folder to your Path environment variable.

PATH S:\thirdparty\icu4c-64_2-Win64-MSVC2017\bin64;%PATH%

4. Fetch SQLite3

(New-Object System.Net.WebClient).DownloadFile("https://www.sqlite.org/2019/sqlite-amalgamation-3270200.zip", "S:\sqlite-amalgamation-3270200.zip")
Add-Type -A System.IO.Compression.FileSystem
[IO.Compression.ZipFile]::ExtractToDirectory("S:\sqlite-amalgamation-3270200.zip", "S:\")

5. Get ready

From within a developer command prompt (not PowerShell nor cmd, but the Visual Studio Developer Command Prompt), execute the following command if you have an x64 PC.

VsDevCmd -arch=amd64

If instead you're compiling for a 32-bit Windows target, adapt the arch argument to x86 and run

VsDevCmd -arch=x86

Decide whether you want to build a release or debug version of Swift on Windows and replace the CMAKE_BUILD_TYPE parameter in the build steps below with the correct value (Debug, RelWithDebInfoAssert or Release) to avoid conflicts between the debug and non-debug version of the MSCRT library.
Set up the ucrt, visualc, and WinSDK modules by copying ucrt.modulemap located at swift/stdlib/public/Platform/ucrt.modulemap into ${UniversalCRTSdkDir}/Include/${UCRTVersion}/ucrt as module.modulemap, copying visualc.modulemap located at swift/stdlib/public/Platform/visualc.modulemap into ${VCToolsInstallDir}/include as module.modulemap, and copying winsdk.modulemap located at swift/stdlib/public/Platform/winsdk.modulemap into ${UniversalCRTSdkDir}/Include/${UCRTVersion}/um and setup the visualc.apinotes located at swift/stdlib/public/Platform/visualc.apinotes into ${VCToolsInstallDir}/include as visualc.apinotes

mklink "%UniversalCRTSdkDir%\Include\%UCRTVersion%\ucrt\module.modulemap" S:\swift\stdlib\public\Platform\ucrt.modulemap
mklink "%UniversalCRTSdkDir%\Include\%UCRTVersion%\um\module.modulemap" S:\swift\stdlib\public\Platform\winsdk.modulemap
mklink "%VCToolsInstallDir%\include\module.modulemap" S:\swift\stdlib\public\Platform\visualc.modulemap
mklink "%VCToolsInstallDir%\include\visualc.apinotes" S:\swift\stdlib\public\Platform\visualc.apinotes

Warning: Creating the above links usually requires administrator privileges. The quick and easy way to do this is to open a second developer prompt by right clicking whatever shortcut you used to open the first one, choosing Run As Administrator, and pasting the above commands into the resulting window. You can then close the privileged prompt; this is the only step which requires elevation.

6. Build LLVM/Clang

This must be done from within a developer command prompt. Make sure that the build type for LLVM/Clang is compatible with the build type for Swift. That is, either build everything Debug or some variant of Release (e.g. Release, RelWithDebInfo).

md "S:\b\llvm"
cd "S:\b\llvm"
cmake -G Ninja^
 -DCMAKE_BUILD_TYPE=Release^
 -DCMAKE_C_COMPILER=cl^
 -DCMAKE_CXX_COMPILER=cl^
 -DLLVM_DEFAULT_TARGET_TRIPLE=x86_64-unknown-windows-msvc^
 -DLLVM_ENABLE_ASSERTIONS=ON^
 -DLLVM_ENABLE_PDB=YES^
 -DLLVM_ENABLE_PROJECTS=clang^
 -DLLVM_TARGETS_TO_BUILD="AArch64;ARM;X86"^
 S:/llvm
ninja

Update your path to include the LLVM tools.

path S:\b\llvm\bin;%PATH%

7. Build CMark

This must be done from within a developer command prompt.

md "S:\b\cmark"
cd "S:\b\cmark"
cmake -G Ninja^
  -DCMAKE_BUILD_TYPE=RelWithDebInfo^
  -DCMAKE_C_COMPILER=cl^
  -DCMAKE_CXX_COMPILER=cl^
  S:\cmark
ninja

8. Build Swift

This must be done from within a developer command prompt
Note that Visual Studio vends a 32-bit python 2.7 installation in C:\Python27 and a 64-bit python in C:\Python27amd64. You may use either one based on your installation.

md "S:\b\swift"
cd "S:\b\swift"
cmake -G Ninja^
 -DCMAKE_BUILD_TYPE=RelWithDebInfo^
 -DCMAKE_C_COMPILER=cl^
 -DCMAKE_CXX_COMPILER=cl^
 -DCMAKE_EXE_LINKER_FLAGS:STRING="/INCREMENTAL:NO"^
 -DCMAKE_SHARED_LINKER_FLAGS:STRING="/INCREMENTAL:NO"^
 -DSWIFT_INCLUDE_DOCS=OFF^
 -DSWIFT_PATH_TO_CMARK_SOURCE="S:\cmark"^
 -DSWIFT_PATH_TO_CMARK_BUILD="S:\b\cmark"^
 -DLLVM_DIR=S:\b\llvm\lib\cmake\llvm^
 -DClang_DIR=S:\b\llvm\lib\cmake\clang^
 -DSWIFT_PATH_TO_LIBDISPATCH_SOURCE="S:\swift-corelibs-libdispatch"^
 -DSWIFT_WINDOWS_x86_64_ICU_UC_INCLUDE="S:/thirdparty/icu4c-64_2-Win64-MSVC2017/include"^
 -DSWIFT_WINDOWS_x86_64_ICU_UC="S:/thirdparty/icu4c-64_2-Win64-MSVC2017/lib64/icuuc.lib"^
 -DSWIFT_WINDOWS_x86_64_ICU_I18N_INCLUDE="S:/thirdparty/icu4c-64_2-Win64-MSVC2017/include"^
 -DSWIFT_WINDOWS_x86_64_ICU_I18N="S:/thirdparty/icu4c-64_2-Win64-MSVC2017/lib64/icuin.lib"^
 -DCMAKE_INSTALL_PREFIX="C:\Library\Developer\Toolchains\unknown-Asserts-development.xctoolchain\usr"^
 -DPYTHON_EXECUTABLE=C:\Python27\python.exe^
 S:\swift
ninja

To create a Visual Studio project, you'll need to change the generator and, if you have a 64 bit processor, specify the generator platform. Note that you may get multiple build errors compiling the swift project due to an MSBuild limitation that file paths cannot exceed 260 characters. These can be ignored, as they occur after the build when writing the last build status to a file.

cmake -G "Visual Studio 2017" -A x64 -T "host=x64"^ ...

9. Build lldb

This must be done from within a developer command prompt.

md "S:\b\lldb"
cd "S:\b\lldb"
cmake -G Ninja^
  -DLLVM_DIR="S:/b/llvm/lib/cmake/llvm"^
  -DClang_DIR="S:/b/llvm/lib/cmake/clang"^
  -DSwift_DIR="S:/b/swift/lib/cmake/swift"^
  -DCMAKE_BUILD_TYPE=RelWithDebInfo^
  -DLLDB_ALLOW_STATIC_BINDINGS=YES^
  -DLLVM_ENABLE_ASSERTIONS=ON^
  -DPYTHON_HOME="%ProgramFiles(x86)%\Microsoft Visual Studio\Shared\Python37_64"^
  S:\lldb
ninja

10. Running tests on Windows

Running the testsuite on Windows has additional external dependencies.

path S:\thirdparty\icu4c-64_2-Win64-MSVC2017\bin64;S:\b\swift\bin;S:\b\swift\libdispatch-prefix\bin;%PATH%;%ProgramFiles%\Git\usr\bin
ninja -C S:\b\swift check-swift

11. Build swift-corelibs-libdispatch

md "S:\b\libdispatch"
cd "S:\b\libdispatch"
cmake -G Ninja^
  -DCMAKE_BUILD_TYPE=RelWithDebInfo^
  -DCMAKE_C_COMPILER=clang-cl^
  -DCMAKE_CXX_COMPILER=clang-cl^
  -DCMAKE_SWIFT_COMPILER=S:\b\swift\bin\swiftc.exe^
  -DENABLE_SWIFT=ON^
  -DENABLE_TESTING=OFF^
  S:\swift-corelibs-libdispatch
ninja

Add libdispatch to your path:

path S:\b\libdispatch;S:\b\libdispatch\src;%PATH%

12. Build curl

cd "S:\curl"
.\buildconf.bat
cd winbuild
nmake /f Makefile.vc mode=static VC=15 MACHINE=x64

13. Build libxml2

cd "S:\libxml2\win32"
cscript //E:jscript configure.js iconv=no
nmake /f Makefile.msvc

14. Build swift-corelibs-foundation

md "S:\b\foundation"
cd "S:\b\foundation
cmake -G Ninja^
  -DCMAKE_BUILD_TYPE=RelWithDebInfo^
  -DCMAKE_C_COMPILER=clang-cl^
  -DCMAKE_SWIFT_COMPILER=S:\b\swift\bin\swiftc.exe^
  -DCURL_LIBRARY="S:/curl/builds/libcurl-vc15-x64-release-static-ipv6-sspi-winssl/lib/libcurl_a.lib"^
  -DCURL_INCLUDE_DIR="S:/curl/builds/libcurl-vc15-x64-release-static-ipv6-sspi-winssl/include"^
  -DENABLE_TESTING=NO^
  -DICU_ROOT="S:/thirdparty/icu4c-64_2-Win64-MSVC2017"^
  -DLIBXML2_LIBRARY="S:/libxml2/win32/bin.msvc/libxml2_a.lib"^
  -DLIBXML2_INCLUDE_DIR="S:/libxml2/include"^
  -DFOUNDATION_PATH_TO_LIBDISPATCH_SOURCE=S:\swift-corelibs-libdispatch^
  -DFOUNDATION_PATH_TO_LIBDISPATCH_BUILD=S:\b\libdispatch^
   S:\swift-corelibs-foundation
ninja

Add Foundation to your path:

path S:\b\foundation;%PATH%

15. Build swift-corelibs-xctest

md "S:\b\xctest"
cd "S:\b\xctest"
cmake -G Ninja^
  -DBUILD_SHARED_LIBS=YES^
  -DCMAKE_BUILD_TYPE=RelWithDebInfo^
  -DCMAKE_SWIFT_COMPILER=S:\b\swift\bin\swiftc.exe^
  -DXCTEST_PATH_TO_FOUNDATION_BUILD=S:\b\foundation^
  -DXCTEST_PATH_TO_LIBDISPATCH_SOURCE=S:\swift-corelibs-libdispatch^
  -DXCTEST_PATH_TO_LIBDISPATCH_BUILD=S:\b\libdispatch^
  -DLIT_COMMAND=S:\llvm\utils\lit\lit.py^
  -DPYTHON_EXECUTABLE=C:\Python27\python.exe^
  S:\swift-corelibs-xctest
ninja

Add XCTest to your path:

path S:\b\xctest;%PATH%

16. Test XCTest

ninja -C S:\b\xctest check-xctest

17. Rebuild Foundation

cd "S:\b\foundation
cmake -G Ninja^
  -DCMAKE_BUILD_TYPE=RelWithDebInfo^
  -DCMAKE_C_COMPILER=clang-cl^
  -DCMAKE_SWIFT_COMPILER=S:\b\swift\bin\swiftc.exe^
  -DCURL_LIBRARY="S:/curl/builds/libcurl-vc15-x64-release-static-ipv6-sspi-winssl/lib/libcurl_a.lib"^
  -DCURL_INCLUDE_DIR="S:/curl/builds/libcurl-vc15-x64-release-static-ipv6-sspi-winssl/include"^
  -DENABLE_TESTING=YES^
  -DICU_ROOT="S:/thirdparty/icu4c-64_2-Win64-MSVC2017"^
  -DLIBXML2_LIBRARY="S:/libxml2/win32/bin.msvc/libxml2_a.lib"^
  -DLIBXML2_INCLUDE_DIR="S:/libxml2/include"^
  -DFOUNDATION_PATH_TO_LIBDISPATCH_SOURCE=S:\swift-corelibs-libdispatch^
  -DFOUNDATION_PATH_TO_LIBDISPATCH_BUILD=S:\b\libdispatch^
  -DFOUNDATION_PATH_TO_XCTEST_BUILD=S:\b\xctest^
   S:\swift-corelibs-foundation
ninja

18. Test Foundation

cmake --build S:\b\foundation
ninja -C S:\b\foundation test

19. Build SQLite3

md S:\b\sqlite
cd S:\b\sqlite
cl /MD /Ox /Zi /LD /DSQLITE_API=__declspec(dllexport) S:\sqlite-amalgamation-3270200\sqlite3.c

Add SQLite3 to your path:

path S:\b\sqlite;%PATH%

20. Build llbuild

md S:\b\llbuild
cd S:\b\llbuild
set AR=llvm-ar
cmake -G Ninja^
  -DCMAKE_BUILD_TYPE=RelWithDebInfo^
  -DCMAKE_C_COMPILER=cl^
  -DCMAKE_CXX_COMPILER=cl^
  -DFOUNDATION_BUILD_DIR=S:\b\foundation^
  -DLIBDISPATCH_BUILD_DIR=S:\b\libdispatch^
  -DLIBDISPATCH_SOURCE_DIR=S:\swift-corelibs-libdispatch^
  -DSQLite3_INCLUDE_DIR=S:\sqlite-amalgamation-3270200^
  -DSQLite3_LIBRARY=S:\b\sqlite\sqlite3.lib^
  -DLLBUILD_SUPPORT_BINDINGS=Swift^
  S:\llbuild
ninja

Add llbuild to your path:

path S:\b\llbuild\bin;%PATH%

21. Build swift-package-manager

md S:\b\spm
cd S:\b\spm
C:\Python27\python.exe S:\swift-package-manager\Utilities\bootstrap --foundation S:\b\foundation --libdispatch-build-dir S:\b\libdispatch --libdispatch-source-dir S:\swift-corelibs-libdispatch --llbuild-build-dir S:\b\llbuild --llbuild-source-dir S:\llbuild --sqlite-build-dir S:\b\sqlite --sqlite-source-dir S:\sqlite-amalgamation-3270200

22. Install Swift on Windows

Run ninja install:

ninja -C S:\b\swift install

Add the Swift on Windows binaries path (C:\Library\Developer\Toolchains\unknown-Asserts-development.xctoolchain\usr\bin) to the PATH environment variable.

Resuming Builds

If you resume development from a new shell, the path will need to be readjusted. The following will add the correct search order to the path:

path S:\thirdparty\icu4c-63_1-Win64-MSVC2017\bin64;S:\b\llvm\bin;S:\b\swift\bin;S:\b\libdispatch;S:\b\libdispatch\src;S:\b\foundation;S:\b\xctest;S:\b\llbuild\bin;S:\b\sqlite;%PATH%;%ProgramFiles%\Git\usr\bin