Cross toolchain configuration for using clang-cl on non-Windows hosts to target MSVC.

Based on the CMake toolchain file of the LLVM project

https://github.com/llvm-mirror/llvm/blob/master/cmake/platforms/WinMsvc.cmake

Usage

cmake -G Ninja
   -DCMAKE_TOOLCHAIN_FILE=/path/to/clang-cl-msvc.cmake
   -DHOST_ARCH=[arm64|armv7|arm|i686|x86|x86_64|x64]
   -DMSVC_BASE=/path/to/msvc
   -DWINSDK_BASE=/path/to/winsdk
   -DWINSDK_VER=windows sdk version folder name
   -DLLVM_VER=7
   -DCLANG_VER=7

HOST_ARCH:

The architecture to build for.

MSVC_BASE:

Absolute path to the folder containing MSVC headers and system libraries. The layout of the folder matches that which is intalled by MSVC 2017 on Windows, and should look like this:

${MSVC_BASE}
  include
    vector
    stdint.h
    etc...
  lib
    x64
      libcmt.lib
      msvcrt.lib
      etc...
    x86
      libcmt.lib
      msvcrt.lib
      etc...

For versions of MSVC < 2017, or where you have a hermetic toolchain in a custom format, you must use symlinks or restructure it to look like the above.

WINSDK_BASE:

Together with WINSDK_VER, determines the location of Windows SDK headers and libraries.

WINSDK_VER:

Together with WINSDK_BASE, determines the locations of Windows SDK headers and libraries.

WINSDK_BASE and WINSDK_VER work together to define a folder layout that matches that of the Windows SDK installation on a standard Windows machine. It should match the layout described below.

Note that if you install Windows SDK to a windows machine and simply copy the files, it will already be in the correct layout.

${WINSDK_BASE}
  Include
    ${WINSDK_VER}
      shared
      ucrt
      um
        windows.h
        etc...
  Lib
    ${WINSDK_VER}
      ucrt
        x64
        x86
          ucrt.lib
          etc...
      um
        x64
        x86
          kernel32.lib
          etc

IMPORTANT: In order for this to work, you will need a valid copy of the Windows SDK and C++ STL headers and libraries on your host. Additionally, since the Windows libraries and headers are not case-correct, this toolchain file sets up a VFS overlay for the SDK headers and case-correcting symlinks for the libraries when running on a case-sensitive filesystem.

LLVM_VER (optional):

Version of the LLVM/LLD installation on the machine, it assumes version 7 in case it is not set.

CLANG_VER (optional):

Version of the clang(-cl) installation on the machine, it assumes version 7 in case it is not set.

Obtaining the llvm/clang toolchain

The LLVM/Clang toolchain apt repositories can be found at:

http://apt.llvm.org/

The following packages are required to be present on your system:

• llvm-7
• clang-7
• clang-tools-7

Obtaining the Windows SDK and MSVC files

The Windows SDK can downloaded directly from Microsoft at:

https://developer.microsoft.com/en-us/windows/downloads/windows-10-sdk

The MSVC Base files can be obtained from any recent installation of Visual Studio assuming the VC++ components have been installed. The files can generally be found at the following location on your machine:

C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\VC\Tools\MSVC

Examples

Using a makefile for building a project on debian9 for win32

.PHONY: all clean clang-msvc-sdk

MSVC_SDK_URL={Git URL to a copy of this repository which includes the MSVC SDK}

HOSTS=win32-clang deb9
BUILD_TYPES=debug release

TARGETS=$(foreach h,$(HOSTS),$(addprefix $(h)-,$(BUILD_TYPES)))

define build_type
$(subst r,R,$(subst d,D,$(subst /,,$(lastword $(subst -, ,$(dir $1))))))
endef
 
.SECONDEXPANSION:
$(TARGETS): build/$$@/build.ninja
    @cmake --build build/$@

.clang-msvc-sdk:
    git clone $(MSVC_SDK_URL) .clang-msvc-sdk

clang-msvc-sdk: .clang-msvc-sdk
    @cd .clang-msvc-sdk && git pull

build/deb9-%/build.ninja: Makefile
    @mkdir -p $(dir $@)
    @cd $(dir $@) && cmake ../.. -G Ninja \
        -DCMAKE_BUILD_TYPE=$(call build_type,$@)

build/win32-clang-%/build.ninja: Makefile .clang-msvc-sdk
    @mkdir -p $(dir $@)
    @cd $(dir $@) && cmake ../.. -G Ninja \
        -DCMAKE_BUILD_TYPE=$(call build_type,$@) \
        -DCMAKE_TOOLCHAIN_FILE=$(abspath .clang-msvc-sdk)/clang-cl-msvc.cmake \
        -DMSVC_BASE=$(abspath .clang-msvc-sdk)/msvc/14.14.26428 \
        -DWINSDK_BASE=$(abspath .clang-msvc-sdk)/winsdk \
        -DWINSDK_VER=10.0.17134.0 \
        -DHOST_ARCH=x86

The above make file provides the following targets:

$ make
all                          win32-clang-debug          deb9-debug
clang-msvc-sdk               win32-clang-release        deb9-release
clean