1# Cross toolchain configuration for using clang-cl on non-Windows hosts to 2# target MSVC. 3# 4# Usage: 5# cmake -G Ninja 6# -DCMAKE_TOOLCHAIN_FILE=/path/to/this/file 7# -DHOST_ARCH=[aarch64|arm64|armv7|arm|i686|x86|x86_64|x64] 8# -DLLVM_NATIVE_TOOLCHAIN=/path/to/llvm/installation 9# -DMSVC_BASE=/path/to/MSVC/system/libraries/and/includes 10# -DWINSDK_BASE=/path/to/windows-sdk 11# -DWINSDK_VER=windows sdk version folder name 12# 13# HOST_ARCH: 14# The architecture to build for. 15# 16# LLVM_NATIVE_TOOLCHAIN: 17# *Absolute path* to a folder containing the toolchain which will be used to 18# build. At a minimum, this folder should have a bin directory with a 19# copy of clang-cl, clang, clang++, and lld-link, as well as a lib directory 20# containing clang's system resource directory. 21# 22# MSVC_BASE: 23# *Absolute path* to the folder containing MSVC headers and system libraries. 24# The layout of the folder matches that which is intalled by MSVC 2017 on 25# Windows, and should look like this: 26# 27# ${MSVC_BASE} 28# include 29# vector 30# stdint.h 31# etc... 32# lib 33# x64 34# libcmt.lib 35# msvcrt.lib 36# etc... 37# x86 38# libcmt.lib 39# msvcrt.lib 40# etc... 41# 42# For versions of MSVC < 2017, or where you have a hermetic toolchain in a 43# custom format, you must use symlinks or restructure it to look like the above. 44# 45# WINSDK_BASE: 46# Together with WINSDK_VER, determines the location of Windows SDK headers 47# and libraries. 48# 49# WINSDK_VER: 50# Together with WINSDK_BASE, determines the locations of Windows SDK headers 51# and libraries. 52# 53# WINSDK_BASE and WINSDK_VER work together to define a folder layout that matches 54# that of the Windows SDK installation on a standard Windows machine. It should 55# match the layout described below. 56# 57# Note that if you install Windows SDK to a windows machine and simply copy the 58# files, it will already be in the correct layout. 59# 60# ${WINSDK_BASE} 61# Include 62# ${WINSDK_VER} 63# shared 64# ucrt 65# um 66# windows.h 67# etc... 68# Lib 69# ${WINSDK_VER} 70# ucrt 71# x64 72# x86 73# ucrt.lib 74# etc... 75# um 76# x64 77# x86 78# kernel32.lib 79# etc 80# 81# IMPORTANT: In order for this to work, you will need a valid copy of the Windows 82# SDK and C++ STL headers and libraries on your host. Additionally, since the 83# Windows libraries and headers are not case-correct, this toolchain file sets 84# up a VFS overlay for the SDK headers and case-correcting symlinks for the 85# libraries when running on a case-sensitive filesystem. 86 87 88# When configuring CMake with a toolchain file against a top-level CMakeLists.txt, 89# it will actually run CMake many times, once for each small test program used to 90# determine what features a compiler supports. Unfortunately, none of these 91# invocations share a CMakeCache.txt with the top-level invocation, meaning they 92# won't see the value of any arguments the user passed via -D. Since these are 93# necessary to properly configure MSVC in both the top-level configuration as well as 94# all feature-test invocations, we set environment variables with the values so that 95# these environments get inherited by child invocations. 96function(init_user_prop prop) 97 if(${prop}) 98 set(ENV{_${prop}} "${${prop}}") 99 else() 100 set(${prop} "$ENV{_${prop}}" PARENT_SCOPE) 101 endif() 102endfunction() 103 104function(generate_winsdk_vfs_overlay winsdk_include_dir output_path) 105 set(include_dirs) 106 file(GLOB_RECURSE entries LIST_DIRECTORIES true "${winsdk_include_dir}/*") 107 foreach(entry ${entries}) 108 if(IS_DIRECTORY "${entry}") 109 list(APPEND include_dirs "${entry}") 110 endif() 111 endforeach() 112 113 file(WRITE "${output_path}" "version: 0\n") 114 file(APPEND "${output_path}" "case-sensitive: false\n") 115 file(APPEND "${output_path}" "roots:\n") 116 117 foreach(dir ${include_dirs}) 118 file(GLOB headers RELATIVE "${dir}" "${dir}/*.h") 119 if(NOT headers) 120 continue() 121 endif() 122 123 file(APPEND "${output_path}" " - name: \"${dir}\"\n") 124 file(APPEND "${output_path}" " type: directory\n") 125 file(APPEND "${output_path}" " contents:\n") 126 127 foreach(header ${headers}) 128 file(APPEND "${output_path}" " - name: \"${header}\"\n") 129 file(APPEND "${output_path}" " type: file\n") 130 file(APPEND "${output_path}" " external-contents: \"${dir}/${header}\"\n") 131 endforeach() 132 endforeach() 133endfunction() 134 135function(generate_winsdk_lib_symlinks winsdk_um_lib_dir output_dir) 136 execute_process(COMMAND "${CMAKE_COMMAND}" -E make_directory "${output_dir}") 137 file(GLOB libraries RELATIVE "${winsdk_um_lib_dir}" "${winsdk_um_lib_dir}/*") 138 foreach(library ${libraries}) 139 string(TOLOWER "${library}" symlink_name) 140 execute_process(COMMAND "${CMAKE_COMMAND}" 141 -E create_symlink 142 "${winsdk_um_lib_dir}/${library}" 143 "${output_dir}/${symlink_name}") 144 endforeach() 145endfunction() 146 147set(CMAKE_SYSTEM_NAME Windows) 148set(CMAKE_SYSTEM_VERSION 10.0) 149set(CMAKE_SYSTEM_PROCESSOR AMD64) 150 151init_user_prop(HOST_ARCH) 152init_user_prop(LLVM_NATIVE_TOOLCHAIN) 153init_user_prop(MSVC_BASE) 154init_user_prop(WINSDK_BASE) 155init_user_prop(WINSDK_VER) 156 157if(NOT HOST_ARCH) 158 set(HOST_ARCH x86_64) 159endif() 160if(HOST_ARCH STREQUAL "aarch64" OR HOST_ARCH STREQUAL "arm64") 161 set(TRIPLE_ARCH "aarch64") 162 set(WINSDK_ARCH "arm64") 163elseif(HOST_ARCH STREQUAL "armv7" OR HOST_ARCH STREQUAL "arm") 164 set(TRIPLE_ARCH "armv7") 165 set(WINSDK_ARCH "arm") 166elseif(HOST_ARCH STREQUAL "i686" OR HOST_ARCH STREQUAL "x86") 167 set(TRIPLE_ARCH "i686") 168 set(WINSDK_ARCH "x86") 169elseif(HOST_ARCH STREQUAL "x86_64" OR HOST_ARCH STREQUAL "x64") 170 set(TRIPLE_ARCH "x86_64") 171 set(WINSDK_ARCH "x64") 172else() 173 message(SEND_ERROR "Unknown host architecture ${HOST_ARCH}. Must be aarch64 (or arm64), armv7 (or arm), i686 (or x86), or x86_64 (or x64).") 174endif() 175 176set(MSVC_INCLUDE "${MSVC_BASE}/include") 177set(MSVC_LIB "${MSVC_BASE}/lib") 178set(WINSDK_INCLUDE "${WINSDK_BASE}/Include/${WINSDK_VER}") 179set(WINSDK_LIB "${WINSDK_BASE}/Lib/${WINSDK_VER}") 180 181# Do some sanity checking to make sure we can find a native toolchain and 182# that the Windows SDK / MSVC STL directories look kosher. 183if(NOT EXISTS "${LLVM_NATIVE_TOOLCHAIN}/bin/clang-cl" OR 184 NOT EXISTS "${LLVM_NATIVE_TOOLCHAIN}/bin/lld-link") 185 message(SEND_ERROR 186 "LLVM_NATIVE_TOOLCHAIN folder '${LLVM_NATIVE_TOOLCHAIN}' does not " 187 "point to a valid directory containing bin/clang-cl and bin/lld-link " 188 "binaries") 189endif() 190 191if(NOT EXISTS "${MSVC_BASE}" OR 192 NOT EXISTS "${MSVC_INCLUDE}" OR 193 NOT EXISTS "${MSVC_LIB}") 194 message(SEND_ERROR 195 "CMake variable MSVC_BASE must point to a folder containing MSVC " 196 "system headers and libraries") 197endif() 198 199if(NOT EXISTS "${WINSDK_BASE}" OR 200 NOT EXISTS "${WINSDK_INCLUDE}" OR 201 NOT EXISTS "${WINSDK_LIB}") 202 message(SEND_ERROR 203 "CMake variable WINSDK_BASE and WINSDK_VER must resolve to a valid " 204 "Windows SDK installation") 205endif() 206 207if(NOT EXISTS "${WINSDK_INCLUDE}/um/Windows.h") 208 message(SEND_ERROR "Cannot find Windows.h") 209endif() 210if(NOT EXISTS "${WINSDK_INCLUDE}/um/WINDOWS.H") 211 set(case_sensitive_filesystem TRUE) 212endif() 213 214set(CMAKE_C_COMPILER "${LLVM_NATIVE_TOOLCHAIN}/bin/clang-cl" CACHE FILEPATH "") 215set(CMAKE_CXX_COMPILER "${LLVM_NATIVE_TOOLCHAIN}/bin/clang-cl" CACHE FILEPATH "") 216set(CMAKE_LINKER "${LLVM_NATIVE_TOOLCHAIN}/bin/lld-link" CACHE FILEPATH "") 217 218# Even though we're cross-compiling, we need some native tools (e.g. llvm-tblgen), and those 219# native tools have to be built before we can start doing the cross-build. LLVM supports 220# a CROSS_TOOLCHAIN_FLAGS_NATIVE argument which consists of a list of flags to pass to CMake 221# when configuring the NATIVE portion of the cross-build. By default we construct this so 222# that it points to the tools in the same location as the native clang-cl that we're using. 223list(APPEND _CTF_NATIVE_DEFAULT "-DCMAKE_ASM_COMPILER=${LLVM_NATIVE_TOOLCHAIN}/bin/clang") 224list(APPEND _CTF_NATIVE_DEFAULT "-DCMAKE_C_COMPILER=${LLVM_NATIVE_TOOLCHAIN}/bin/clang") 225list(APPEND _CTF_NATIVE_DEFAULT "-DCMAKE_CXX_COMPILER=${LLVM_NATIVE_TOOLCHAIN}/bin/clang++") 226 227set(CROSS_TOOLCHAIN_FLAGS_NATIVE "${_CTF_NATIVE_DEFAULT}" CACHE STRING "") 228 229set(COMPILE_FLAGS 230 -D_CRT_SECURE_NO_WARNINGS 231 --target=${TRIPLE_ARCH}-windows-msvc 232 -fms-compatibility-version=19.11 233 -imsvc "${MSVC_INCLUDE}" 234 -imsvc "${WINSDK_INCLUDE}/ucrt" 235 -imsvc "${WINSDK_INCLUDE}/shared" 236 -imsvc "${WINSDK_INCLUDE}/um" 237 -imsvc "${WINSDK_INCLUDE}/winrt") 238 239if(case_sensitive_filesystem) 240 # Ensure all sub-configures use the top-level VFS overlay instead of generating their own. 241 init_user_prop(winsdk_vfs_overlay_path) 242 if(NOT winsdk_vfs_overlay_path) 243 set(winsdk_vfs_overlay_path "${CMAKE_BINARY_DIR}/winsdk_vfs_overlay.yaml") 244 generate_winsdk_vfs_overlay("${WINSDK_BASE}/Include/${WINSDK_VER}" "${winsdk_vfs_overlay_path}") 245 init_user_prop(winsdk_vfs_overlay_path) 246 endif() 247 list(APPEND COMPILE_FLAGS 248 -Xclang -ivfsoverlay -Xclang "${winsdk_vfs_overlay_path}") 249endif() 250 251string(REPLACE ";" " " COMPILE_FLAGS "${COMPILE_FLAGS}") 252 253# We need to preserve any flags that were passed in by the user. However, we 254# can't append to CMAKE_C_FLAGS and friends directly, because toolchain files 255# will be re-invoked on each reconfigure and therefore need to be idempotent. 256# The assignments to the _INITIAL cache variables don't use FORCE, so they'll 257# only be populated on the initial configure, and their values won't change 258# afterward. 259set(_CMAKE_C_FLAGS_INITIAL "${CMAKE_C_FLAGS}" CACHE STRING "") 260set(CMAKE_C_FLAGS "${_CMAKE_C_FLAGS_INITIAL} ${COMPILE_FLAGS}" CACHE STRING "" FORCE) 261 262set(_CMAKE_CXX_FLAGS_INITIAL "${CMAKE_CXX_FLAGS}" CACHE STRING "") 263set(CMAKE_CXX_FLAGS "${_CMAKE_CXX_FLAGS_INITIAL} ${COMPILE_FLAGS}" CACHE STRING "" FORCE) 264 265set(LINK_FLAGS 266 # Prevent CMake from attempting to invoke mt.exe. It only recognizes the slashed form and not the dashed form. 267 /manifest:no 268 269 -libpath:"${MSVC_LIB}/${WINSDK_ARCH}" 270 -libpath:"${WINSDK_LIB}/ucrt/${WINSDK_ARCH}" 271 -libpath:"${WINSDK_LIB}/um/${WINSDK_ARCH}") 272 273if(case_sensitive_filesystem) 274 # Ensure all sub-configures use the top-level symlinks dir instead of generating their own. 275 init_user_prop(winsdk_lib_symlinks_dir) 276 if(NOT winsdk_lib_symlinks_dir) 277 set(winsdk_lib_symlinks_dir "${CMAKE_BINARY_DIR}/winsdk_lib_symlinks") 278 generate_winsdk_lib_symlinks("${WINSDK_BASE}/Lib/${WINSDK_VER}/um/${WINSDK_ARCH}" "${winsdk_lib_symlinks_dir}") 279 init_user_prop(winsdk_lib_symlinks_dir) 280 endif() 281 list(APPEND LINK_FLAGS 282 -libpath:"${winsdk_lib_symlinks_dir}") 283endif() 284 285string(REPLACE ";" " " LINK_FLAGS "${LINK_FLAGS}") 286 287# See explanation for compiler flags above for the _INITIAL variables. 288set(_CMAKE_EXE_LINKER_FLAGS_INITIAL "${CMAKE_EXE_LINKER_FLAGS}" CACHE STRING "") 289set(CMAKE_EXE_LINKER_FLAGS "${_CMAKE_EXE_LINKER_FLAGS_INITIAL} ${LINK_FLAGS}" CACHE STRING "" FORCE) 290 291set(_CMAKE_MODULE_LINKER_FLAGS_INITIAL "${CMAKE_MODULE_LINKER_FLAGS}" CACHE STRING "") 292set(CMAKE_MODULE_LINKER_FLAGS "${_CMAKE_MODULE_LINKER_FLAGS_INITIAL} ${LINK_FLAGS}" CACHE STRING "" FORCE) 293 294set(_CMAKE_SHARED_LINKER_FLAGS_INITIAL "${CMAKE_SHARED_LINKER_FLAGS}" CACHE STRING "") 295set(CMAKE_SHARED_LINKER_FLAGS "${_CMAKE_SHARED_LINKER_FLAGS_INITIAL} ${LINK_FLAGS}" CACHE STRING "" FORCE) 296 297# CMake populates these with a bunch of unnecessary libraries, which requires 298# extra case-correcting symlinks and what not. Instead, let projects explicitly 299# control which libraries they require. 300set(CMAKE_C_STANDARD_LIBRARIES "" CACHE STRING "" FORCE) 301set(CMAKE_CXX_STANDARD_LIBRARIES "" CACHE STRING "" FORCE) 302 303# Allow clang-cl to work with macOS paths. 304set(CMAKE_USER_MAKE_RULES_OVERRIDE "${CMAKE_CURRENT_LIST_DIR}/ClangClCMakeCompileRules.cmake") 305