From d26d6135edeeadc0f4e98ad2008af73cecbc4ff6 Mon Sep 17 00:00:00 2001
From: Mark Schofield <34426337+MarkSchofield@users.noreply.github.com>
Date: Sun, 1 Feb 2026 12:06:04 -0800
Subject: [PATCH] Support Windows.Clang.toolchain.cmake and Windows.Kits.cmake
 consumption from Linux

---
 VSWhere.cmake                                 | 15 +++-
 WSL.cmake                                     | 87 +++++++++++++++++++
 Windows.Clang.toolchain.cmake                 | 41 ++++++---
 Windows.Kits.cmake                            | 39 ++++++---
 example/CMakePresets.json                     | 49 +++++++++++
 example/CommandLineAsm/CMakeLists.txt         |  3 +-
 .../WindowsApplication/WindowsApplication.rc  | 11 +--
 7 files changed, 210 insertions(+), 35 deletions(-)
 create mode 100644 WSL.cmake

diff --git a/VSWhere.cmake b/VSWhere.cmake
index de77c7b..4cbf54a 100644
--- a/VSWhere.cmake
+++ b/VSWhere.cmake
@@ -23,6 +23,8 @@
 #----------------------------------------------------------------------------------------------------------------------
 include_guard()
 
+include("${CMAKE_CURRENT_LIST_DIR}/WSL.cmake")
+
 #[[====================================================================================================================
     toolchain_validate_vs_files
     ---------------------------
@@ -79,12 +81,21 @@ function(findVisualStudio)
 
     cmake_parse_arguments(PARSE_ARGV 0 FIND_VS "${OPTIONS}" "${ONE_VALUE_KEYWORDS}" "${MULTI_VALUE_KEYWORDS}")
 
+    set(VSWHERE_HINT_PATH "$ENV{ProgramFiles\(x86\)}/Microsoft Visual Studio/Installer")
+
+    # Accommodate WSL
+    if((CMAKE_HOST_SYSTEM_NAME STREQUAL "Linux") AND (EXISTS "/usr/bin/wslpath"))
+        toolchain_read_reg_string("HKLM\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion" "ProgramFilesDir (x86)" PROGRAM_FILES_X86_PATH)
+        set(VSWHERE_HINT_PATH "${PROGRAM_FILES_X86_PATH}\\Microsoft Visual Studio\\Installer")
+        toolchain_to_wsl_path("${VSWHERE_HINT_PATH}" VSWHERE_HINT_PATH)
+    endif()
+
     find_program(VSWHERE_PATH
         NAMES vswhere vswhere.exe
-        HINTS "$ENV{ProgramFiles\(x86\)}/Microsoft Visual Studio/Installer"
+        HINTS ${VSWHERE_HINT_PATH}
     )
 
-    if(VSWHERE_PATH STREQUAL "VSWHERE_PATH-NOTFOUND")
+    if(NOT VSWHERE_PATH)
         message(FATAL_ERROR "'vswhere' isn't found.")
     endif()
 
diff --git a/WSL.cmake b/WSL.cmake
new file mode 100644
index 0000000..f74db0d
--- /dev/null
+++ b/WSL.cmake
@@ -0,0 +1,87 @@
+#----------------------------------------------------------------------------------------------------------------------
+# MIT License
+#
+# Copyright (c) 2026 Mark Schofield
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in all
+# copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+#----------------------------------------------------------------------------------------------------------------------
+include_guard()
+
+#[[====================================================================================================================
+    toolchain_read_reg_string
+    -------------------------
+
+    Reads a string value from the Windows registry using reg.exe via WSL.
+
+        toolchain_read_reg_string(
+            <reg_key>
+            <reg_value>
+            <output_variable>
+        )
+
+    Note: Not supported for consumption outside of the toolchain files.
+====================================================================================================================]]#
+function(toolchain_read_reg_string REG_KEY REG_VALUE OUTPUT_VARIABLE)
+    if(CMAKE_HOST_SYSTEM_NAME STREQUAL "Windows")
+        message(FATAL_ERROR "toolchain_read_reg_string should not be used on Windows platforms.")
+    endif()
+
+    find_program(REG_EXE_PATH NAMES reg.exe)
+    if(NOT REG_EXE_PATH)
+        message(FATAL_ERROR "reg.exe not found - cannot read Windows registry from WSL.")
+    endif()
+
+    execute_process(
+        COMMAND ${REG_EXE_PATH} QUERY ${REG_KEY} /v ${REG_VALUE}
+        OUTPUT_VARIABLE REG_OUTPUT
+        OUTPUT_STRIP_TRAILING_WHITESPACE
+    )
+    string(REGEX REPLACE ".*REG_SZ[ \t]+(.*)$" "\\1" REG_OUTPUT "${REG_OUTPUT}")
+    message(VERBOSE "toolchain_read_reg_string: VALUE = ${REG_OUTPUT}")
+    set(${OUTPUT_VARIABLE} "${REG_OUTPUT}" PARENT_SCOPE)
+endfunction()
+
+#[[====================================================================================================================
+    toolchain_to_wsl_path
+    ---------------------
+
+    Converts a Windows path to a WSL path.
+
+        toolchain_to_wsl_path(
+            <input_path>
+            <output_variable>
+        )
+
+    Note: Not supported for consumption outside of the toolchain files.
+====================================================================================================================]]#
+function(toolchain_to_wsl_path INPUT_PATH OUTPUT_VARIABLE)
+    if(CMAKE_HOST_SYSTEM_NAME STREQUAL "Windows")
+        message(FATAL_ERROR "toolchain_to_wsl_path should not be used on Windows platforms.")
+    endif()
+
+    if(NOT (EXISTS "/usr/bin/wslpath"))
+        message(FATAL_ERROR "wslpath not found - cannot convert Windows path to WSL path.")
+    endif()
+
+    execute_process(COMMAND /usr/bin/wslpath -u ${INPUT_PATH}
+            OUTPUT_VARIABLE WSL_PATH
+            OUTPUT_STRIP_TRAILING_WHITESPACE
+    )
+    set(${OUTPUT_VARIABLE} "${WSL_PATH}" PARENT_SCOPE)
+endfunction()
diff --git a/Windows.Clang.toolchain.cmake b/Windows.Clang.toolchain.cmake
index dc0b7b9..ac2c559 100644
--- a/Windows.Clang.toolchain.cmake
+++ b/Windows.Clang.toolchain.cmake
@@ -62,11 +62,6 @@ cmake_minimum_required(VERSION 3.20)
 
 include_guard()
 
-# If `CMAKE_HOST_SYSTEM_NAME` is not 'Windows', there's nothing to do.
-if(NOT (CMAKE_HOST_SYSTEM_NAME STREQUAL Windows))
-    return()
-endif()
-
 option(TOOLCHAIN_UPDATE_PROGRAM_PATH "Whether the toolchain should update CMAKE_PROGRAM_PATH." ON)
 option(TOOLCHAIN_ADD_VS_NINJA_PATH "Whether the toolchain should add the path to the VS Ninja to the CMAKE_SYSTEM_PROGRAM_PATH." ON)
 
@@ -147,6 +142,11 @@ if(NOT VS_INSTALLATION_PATH)
                 installationPath VS_INSTALLATION_PATH
         )
     endif()
+
+    if((CMAKE_HOST_SYSTEM_NAME STREQUAL "Linux") AND (EXISTS "/usr/bin/wslpath"))
+        # Path properties returned by VSWhere are Windows-style paths. Convert to WSL-style paths on WSL.
+        toolchain_to_wsl_path("${VS_INSTALLATION_PATH}" VS_INSTALLATION_PATH)
+    endif()
 endif()
 
 message(VERBOSE "VS_INSTALLATION_VERSION = ${VS_INSTALLATION_VERSION}")
@@ -177,13 +177,23 @@ set(VS_TOOLSET_PATH "${VS_INSTALLATION_PATH}/VC/Tools/MSVC/${CMAKE_VS_PLATFORM_T
 
 # Map CMAKE_SYSTEM_PROCESSOR values to CMAKE_VS_PLATFORM_TOOLSET_ARCHITECTURE that identifies the tools that should
 # be used to produce code for the CMAKE_SYSTEM_PROCESSOR.
-if(CMAKE_SYSTEM_PROCESSOR STREQUAL AMD64)
-    set(CMAKE_VS_PLATFORM_TOOLSET_ARCHITECTURE x64)
-elseif((CMAKE_SYSTEM_PROCESSOR STREQUAL ARM)
-    OR (CMAKE_SYSTEM_PROCESSOR STREQUAL ARM64)
-    OR (CMAKE_SYSTEM_PROCESSOR STREQUAL X86))
-    set(CMAKE_VS_PLATFORM_TOOLSET_ARCHITECTURE ${CMAKE_SYSTEM_PROCESSOR})
-else()
+if(CMAKE_HOST_SYSTEM_NAME STREQUAL "Windows")
+    if(CMAKE_SYSTEM_PROCESSOR STREQUAL AMD64)
+        set(CMAKE_VS_PLATFORM_TOOLSET_ARCHITECTURE x64)
+    elseif((CMAKE_SYSTEM_PROCESSOR STREQUAL ARM)
+        OR (CMAKE_SYSTEM_PROCESSOR STREQUAL ARM64)
+        OR (CMAKE_SYSTEM_PROCESSOR STREQUAL X86))
+        set(CMAKE_VS_PLATFORM_TOOLSET_ARCHITECTURE ${CMAKE_SYSTEM_PROCESSOR})
+    endif()
+elseif(CMAKE_HOST_SYSTEM_NAME STREQUAL "Linux")
+    if(CMAKE_SYSTEM_PROCESSOR STREQUAL aarch64)
+        set(CMAKE_VS_PLATFORM_TOOLSET_ARCHITECTURE ARM64)
+    elseif(CMAKE_SYSTEM_PROCESSOR STREQUAL x86_64)
+        set(CMAKE_VS_PLATFORM_TOOLSET_ARCHITECTURE x64)
+    endif()
+endif()
+
+if(NOT CMAKE_VS_PLATFORM_TOOLSET_ARCHITECTURE)
     message(FATAL_ERROR "Unable identify compiler architecture for CMAKE_SYSTEM_PROCESSOR ${CMAKE_SYSTEM_PROCESSOR}")
 endif()
 
@@ -234,6 +244,13 @@ foreach(LANG C CXX)
     endif()
 endforeach()
 
+# If not compiling on Windows, set the clang compiler target to Windows.
+if(NOT (CMAKE_HOST_SYSTEM_NAME STREQUAL "Windows"))
+    foreach(LANG C CXX)
+        set(CMAKE_${LANG}_COMPILER_TARGET "${CMAKE_SYSTEM_PROCESSOR}-windows-msvc")
+    endforeach()
+endif()
+
 if(VS_USE_SPECTRE_MITIGATION_ATLMFC_RUNTIME)
     # Ensure that the necessary folder and files are present before adding the 'link_directories'
     toolchain_validate_vs_files(
diff --git a/Windows.Kits.cmake b/Windows.Kits.cmake
index 2a6a58b..2504106 100644
--- a/Windows.Kits.cmake
+++ b/Windows.Kits.cmake
@@ -46,6 +46,8 @@
 #
 include_guard()
 
+include("${CMAKE_CURRENT_LIST_DIR}/WSL.cmake")
+
 if(NOT CMAKE_SYSTEM_VERSION)
     set(CMAKE_SYSTEM_VERSION ${CMAKE_HOST_SYSTEM_VERSION})
 endif()
@@ -59,12 +61,19 @@ if(NOT CMAKE_VS_PLATFORM_TOOLSET_HOST_ARCHITECTURE)
 endif()
 
 if(NOT CMAKE_WINDOWS_KITS_10_DIR)
-    get_filename_component(CMAKE_WINDOWS_KITS_10_DIR "[HKEY_LOCAL_MACHINE\\SOFTWARE\\Microsoft\\Microsoft SDKs\\Windows\\v10.0;InstallationFolder]" ABSOLUTE CACHE)
-    if ("${CMAKE_WINDOWS_KITS_10_DIR}" STREQUAL "/registry")
-        unset(CMAKE_WINDOWS_KITS_10_DIR)
+    if((CMAKE_HOST_SYSTEM_NAME STREQUAL "Linux") AND (EXISTS "/usr/bin/wslpath"))
+        toolchain_read_reg_string("HKLM\\SOFTWARE\\WOW6432Node\\Microsoft\\Microsoft SDKs\\Windows\\v10.0" "InstallationFolder" CMAKE_WINDOWS_KITS_10_DIR)
+        message(VERBOSE "Windows.Kits: CMAKE_WINDOWS_KITS_10_DIR (WSL) = ${CMAKE_WINDOWS_KITS_10_DIR}")
+        toolchain_to_wsl_path("${CMAKE_WINDOWS_KITS_10_DIR}" CMAKE_WINDOWS_KITS_10_DIR)
+    else()
+        get_filename_component(CMAKE_WINDOWS_KITS_10_DIR "[HKEY_LOCAL_MACHINE\\SOFTWARE\\Microsoft\\Microsoft SDKs\\Windows\\v10.0;InstallationFolder]" ABSOLUTE CACHE)
+        if ("${CMAKE_WINDOWS_KITS_10_DIR}" STREQUAL "/registry")
+            unset(CMAKE_WINDOWS_KITS_10_DIR)
+        endif()
     endif()
 endif()
 
+message(VERBOSE "Windows.Kits: CMAKE_WINDOWS_KITS_10_DIR = ${CMAKE_WINDOWS_KITS_10_DIR}")
 if(NOT CMAKE_WINDOWS_KITS_10_DIR)
     message(FATAL_ERROR "Unable to find an installed Windows SDK, and one wasn't specified.")
 endif()
@@ -127,13 +136,23 @@ set(MIDL_COMPILER "${WINDOWS_KITS_BIN_PATH}/${CMAKE_VS_PLATFORM_TOOLSET_HOST_ARC
 set(MDMERGE_TOOL "${WINDOWS_KITS_BIN_PATH}/${CMAKE_VS_PLATFORM_TOOLSET_HOST_ARCHITECTURE}/mdmerge.exe")
 
 # Windows SDK
-if(CMAKE_SYSTEM_PROCESSOR STREQUAL AMD64)
-    set(WINDOWS_KITS_TARGET_ARCHITECTURE x64)
-elseif((CMAKE_SYSTEM_PROCESSOR STREQUAL ARM)
-    OR (CMAKE_SYSTEM_PROCESSOR STREQUAL ARM64)
-    OR (CMAKE_SYSTEM_PROCESSOR STREQUAL X86))
-    set(WINDOWS_KITS_TARGET_ARCHITECTURE ${CMAKE_SYSTEM_PROCESSOR})
-else()
+if(CMAKE_HOST_SYSTEM_NAME STREQUAL "Windows")
+    if(CMAKE_SYSTEM_PROCESSOR STREQUAL AMD64)
+        set(WINDOWS_KITS_TARGET_ARCHITECTURE x64)
+    elseif((CMAKE_SYSTEM_PROCESSOR STREQUAL ARM)
+        OR (CMAKE_SYSTEM_PROCESSOR STREQUAL ARM64)
+        OR (CMAKE_SYSTEM_PROCESSOR STREQUAL X86))
+        set(WINDOWS_KITS_TARGET_ARCHITECTURE ${CMAKE_SYSTEM_PROCESSOR})
+    endif()
+elseif(CMAKE_HOST_SYSTEM_NAME STREQUAL "Linux")
+    if(CMAKE_SYSTEM_PROCESSOR STREQUAL aarch64)
+        set(WINDOWS_KITS_TARGET_ARCHITECTURE ARM64)
+    elseif(CMAKE_SYSTEM_PROCESSOR STREQUAL x86_64)
+        set(WINDOWS_KITS_TARGET_ARCHITECTURE x64)
+    endif()
+endif()
+
+if(NOT WINDOWS_KITS_TARGET_ARCHITECTURE)
     message(FATAL_ERROR "Unable identify Windows Kits architecture for CMAKE_SYSTEM_PROCESSOR ${CMAKE_SYSTEM_PROCESSOR}")
 endif()
 
diff --git a/example/CMakePresets.json b/example/CMakePresets.json
index 978f4ac..d50f157 100644
--- a/example/CMakePresets.json
+++ b/example/CMakePresets.json
@@ -22,6 +22,7 @@
     {
       "name": "windows",
       "inherits": ["default"],
+      "condition": { "lhs": "${hostSystemName}", "type": "equals", "rhs": "Windows" },
       "hidden": true
     },
     {
@@ -167,6 +168,46 @@
         "CMAKE_GENERATOR_PLATFORM": "ARM64,version=10.0.26100.0",
         "CMAKE_SYSTEM_PROCESSOR": "ARM64"
       }
+    },
+    {
+      "name": "linux-windows",
+      "inherits": ["default"],
+      "description": "Cross-compiling to Windows from Linux",
+      "condition": { "lhs": "${hostSystemName}", "type": "equals", "rhs": "Linux" },
+      "hidden": true,
+      "cacheVariables": {
+        "CMAKE_SYSTEM_NAME": "Windows"
+      }
+    },
+    {
+      "name": "linux-windows-ninja-clang",
+      "inherits": ["linux-windows"],
+      "generator": "Ninja Multi-Config",
+      "hidden": true,
+      "cacheVariables": {
+        "CMAKE_TOOLCHAIN_FILE": "../Windows.Clang.toolchain.cmake",
+        "CMAKE_C_COMPILER": "clang-20",
+        "CMAKE_CXX_COMPILER": "clang++-20",
+        "CMAKE_LINKER_TYPE": "lld",
+        "CMAKE_MT": "llvm-mt-20",
+        "CMAKE_RC_COMPILER": "llvm-rc-20",
+        "CMAKE_C_USING_LINKER_lld": "-fuse-ld=lld",
+        "CMAKE_CXX_USING_LINKER_lld": "-fuse-ld=lld"
+      }
+    },
+    {
+      "name": "linux-windows-ninja-clang-arm64",
+      "inherits": ["linux-windows-ninja-clang"],
+      "cacheVariables": {
+        "CMAKE_SYSTEM_PROCESSOR": "aarch64"
+      }
+    },
+    {
+      "name": "linux-windows-ninja-clang-x64",
+      "inherits": ["linux-windows-ninja-clang"],
+      "cacheVariables": {
+        "CMAKE_SYSTEM_PROCESSOR": "x86_64"
+      }
     }
   ],
   "buildPresets": [
@@ -213,6 +254,14 @@
     {
       "name": "windows-vs2022-arm64",
       "configurePreset": "windows-vs2022-arm64"
+    },
+    {
+      "name": "linux-windows-ninja-clang-arm64",
+      "configurePreset": "linux-windows-ninja-clang-arm64"
+    },
+    {
+      "name": "linux-windows-ninja-clang-x64",
+      "configurePreset": "linux-windows-ninja-clang-x64"
     }
   ]
 }
diff --git a/example/CommandLineAsm/CMakeLists.txt b/example/CommandLineAsm/CMakeLists.txt
index 8885b51..58c0885 100644
--- a/example/CommandLineAsm/CMakeLists.txt
+++ b/example/CommandLineAsm/CMakeLists.txt
@@ -8,7 +8,8 @@ if((CMAKE_SYSTEM_PROCESSOR STREQUAL AMD64) OR (CMAKE_SYSTEM_PROCESSOR STREQUAL X
 elseif(CMAKE_SYSTEM_PROCESSOR STREQUAL ARM64)
     enable_language(ASM_MARMASM)
 else()
-    message(FATAL_ERROR "Unknown CMAKE_SYSTEM_PROCESSOR for ASM language.")
+    message(STATUS "Unknown CMAKE_SYSTEM_PROCESSOR for ASM language.")
+    return()
 endif()
 
 add_executable(CommandLineAsm
diff --git a/example/WindowsApplication/WindowsApplication.rc b/example/WindowsApplication/WindowsApplication.rc
index 1b0ca25..9e005af 100644
--- a/example/WindowsApplication/WindowsApplication.rc
+++ b/example/WindowsApplication/WindowsApplication.rc
@@ -1,7 +1,7 @@
 //---------------------------------------------------------------------------------------------------------------------
 //
 //---------------------------------------------------------------------------------------------------------------------
-#include "resource.h"
+#include "Resource.h"
 
 #define APSTUDIO_READONLY_SYMBOLS
 #ifndef APSTUDIO_INVOKED
@@ -38,15 +38,6 @@ BEGIN
     END
 END
 
-//---------------------------------------------------------------------------------------------------------------------
-// Accelerator
-//---------------------------------------------------------------------------------------------------------------------
-IDC_WINDOWSAPPLICATION ACCELERATORS
-BEGIN
-    "?",            IDM_ABOUT,              ASCII,  ALT
-    "/",            IDM_ABOUT,              ASCII,  ALT
-END
-
 //---------------------------------------------------------------------------------------------------------------------
 // Dialog
 //---------------------------------------------------------------------------------------------------------------------