CMAKE_CROSSCOMPILING should not be true, if the build targets the hos…

…t processor (#124)
MarkSchofield · Nov 22, 2024 · 88ebf71 · 88ebf71
2 parents 25f97a4 + 35a505e
commit 88ebf71
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Showing 6 changed files with 34 additions and 10 deletions.
diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
@@ -38,6 +38,7 @@ jobs:
           - windows-msvc-spectre-x64
           - windows-msvc-x86
           - windows-msvc-arm64
+          - windows-msvc-host
           - windows-clang-x64
           - windows-clangcl-x64
           - windows-vs-x64

diff --git a/Windows.Clang.toolchain.cmake b/Windows.Clang.toolchain.cmake
@@ -43,7 +43,7 @@
 # | CMAKE_CXX_COMPILER                          | The path to the C++ compiler to use.                                                                  |
 # | CMAKE_MT                                    | The path to the 'mt.exe' tool to use.                                                                 |
 # | CMAKE_RC_COMPILER                           | The path tp the 'rc.exe' tool to use.                                                                 |
-# | CMAKE_SYSTEM_NAME                           | Windows                                                                                               |
+# | CMAKE_SYSTEM_NAME                           | "Windows", when cross-compiling                                                                       |
 # | WIN32                                       | 1                                                                                                     |
 # | CMAKE_CXX_CLANG_TIDY                        | The commandline clang-tidy is used if CLANG_TIDY_CHECKS was set.                                      |
 #
@@ -54,22 +54,28 @@ 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)
 
 set(UNUSED ${CMAKE_TOOLCHAIN_FILE}) # Note: only to prevent cmake unused variable warninig
-set(CMAKE_SYSTEM_NAME Windows)
-set(CMAKE_TRY_COMPILE_PLATFORM_VARIABLES "CMAKE_SYSTEM_PROCESSOR;CMAKE_CROSSCOMPILING")
-set(CMAKE_CROSSCOMPILING TRUE)
+set(CMAKE_TRY_COMPILE_PLATFORM_VARIABLES "CMAKE_SYSTEM_PROCESSOR")
 set(WIN32 1)
 
+# If `CMAKE_SYSTEM_PROCESSOR` isn't set, default to `CMAKE_HOST_SYSTEM_PROCESSOR`
 if(NOT CMAKE_SYSTEM_PROCESSOR)
     set(CMAKE_SYSTEM_PROCESSOR ${CMAKE_HOST_SYSTEM_PROCESSOR})
 endif()
 
+# If `CMAKE_SYSTEM_PROCESSOR` is not equal to `CMAKE_HOST_SYSTEM_PROCESSOR`, this is cross-compilation.
+# CMake expects `CMAKE_SYSTEM_NAME` to be set to reflect cross-compilation.
+if(NOT (CMAKE_SYSTEM_PROCESSOR STREQUAL ${CMAKE_HOST_SYSTEM_PROCESSOR}))
+    set(CMAKE_SYSTEM_NAME Windows)
+endif()
+
 if(NOT CMAKE_VS_VERSION_RANGE)
     set(CMAKE_VS_VERSION_RANGE "[16.0,)")
 endif()

diff --git a/Windows.EWDK.toolchain.cmake b/Windows.EWDK.toolchain.cmake
@@ -52,7 +52,7 @@
 # | CMAKE_CXX_COMPILER                          | The path to the C++ compiler to use.                                                                  |
 # | CMAKE_MT                                    | The path to the 'mt.exe' tool to use.                                                                 |
 # | CMAKE_RC_COMPILER                           | The path tp the 'rc.exe' tool to use.                                                                 |
-# | CMAKE_SYSTEM_NAME                           | 'Windows'                                                                                             |
+# | CMAKE_SYSTEM_NAME                           | "Windows", when cross-compiling                                                                       |
 # | CMAKE_SYSTEM_PROCESSOR                      | The architecture to build for (e.g. ARM64).                                                           |
 # | CMAKE_VS_PLATFORM_TOOLSET_HOST_ARCHITECTURE | The architecture of the host tooling to use (e.g. x86).                                               |
 # | CMAKE_VS_PLATFORM_TOOLSET_VERSION           | The version of the MSVC platform toolset to use (e.g. 14.31.31103).                                   |

diff --git a/Windows.MSVC.toolchain.cmake b/Windows.MSVC.toolchain.cmake
@@ -51,7 +51,7 @@
 # | CMAKE_CXX_COMPILER                          | The path to the C++ compiler to use.                                                                  |
 # | CMAKE_MT                                    | The path to the 'mt.exe' tool to use.                                                                 |
 # | CMAKE_RC_COMPILER                           | The path tp the 'rc.exe' tool to use.                                                                 |
-# | CMAKE_SYSTEM_NAME                           | Windows                                                                                               |
+# | CMAKE_SYSTEM_NAME                           | "Windows", when cross-compiling                                                                       |
 # | CMAKE_VS_PLATFORM_TOOLSET_VERSION           | The version of the MSVC toolset being used - e.g. 14.29.30133.                                        |
 # | WIN32                                       | 1                                                                                                     |
 # | MSVC                                        | 1                                                                                                     |
@@ -69,16 +69,15 @@ 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)
 
 set(UNUSED ${CMAKE_TOOLCHAIN_FILE}) # Note: only to prevent cmake unused variable warninig
-set(CMAKE_SYSTEM_NAME Windows)
 set(CMAKE_TRY_COMPILE_PLATFORM_VARIABLES
-    CMAKE_CROSSCOMPILING
     CMAKE_SYSTEM_PROCESSOR
     CMAKE_VS_PLATFORM_TOOLSET_HOST_ARCHITECTURE
     CMAKE_VS_PRODUCTS
@@ -88,16 +87,22 @@ set(CMAKE_TRY_COMPILE_PLATFORM_VARIABLES
     VS_INSTALLATION_VERSION
     VS_PLATFORM_TOOLSET_VERSION
 )
-set(CMAKE_CROSSCOMPILING TRUE)
 set(WIN32 1)
 set(MSVC 1)
 
 include("${CMAKE_CURRENT_LIST_DIR}/VSWhere.cmake")
 
+# If `CMAKE_SYSTEM_PROCESSOR` isn't set, default to `CMAKE_HOST_SYSTEM_PROCESSOR`
 if(NOT CMAKE_SYSTEM_PROCESSOR)
     set(CMAKE_SYSTEM_PROCESSOR ${CMAKE_HOST_SYSTEM_PROCESSOR})
 endif()
 
+# If `CMAKE_SYSTEM_PROCESSOR` is not equal to `CMAKE_HOST_SYSTEM_PROCESSOR`, this is cross-compilation.
+# CMake expects `CMAKE_SYSTEM_NAME` to be set to reflect cross-compilation.
+if(NOT (CMAKE_SYSTEM_PROCESSOR STREQUAL ${CMAKE_HOST_SYSTEM_PROCESSOR}))
+    set(CMAKE_SYSTEM_NAME Windows)
+endif()
+
 if(NOT CMAKE_VS_VERSION_RANGE)
     set(CMAKE_VS_VERSION_RANGE "[16.0,)")
 endif()

diff --git a/example/CMakeLists.txt b/example/CMakeLists.txt
@@ -11,9 +11,11 @@ project(WindowsToolchainExample)
 
 # Write properties that are influenced by the toolchain
 #
+message(STATUS "CMAKE_CROSSCOMPILING = ${CMAKE_CROSSCOMPILING}")
+message(STATUS "CMAKE_SYSTEM_NAME = ${CMAKE_SYSTEM_NAME}")
 message(STATUS "CMAKE_SYSTEM_PROCESSOR = ${CMAKE_SYSTEM_PROCESSOR}")
-message(STATUS "MSVC_VERSION = ${MSVC_VERSION}")
 message(STATUS "MSVC_TOOLSET_VERSION = ${MSVC_TOOLSET_VERSION}")
+message(STATUS "MSVC_VERSION = ${MSVC_VERSION}")
 
 # Demonstrate that toolchain-related tooling can be found
 #

diff --git a/example/CMakePresets.json b/example/CMakePresets.json
@@ -100,6 +100,12 @@
         "CMAKE_SYSTEM_PROCESSOR": "ARM64"
       }
     },
+    {
+      "name": "windows-msvc-host",
+      "inherits": "windows-msvc",
+      "displayName": "Configure for 'windows-msvc-host'",
+      "binaryDir": "${sourceDir}/__output/${presetName}"
+    },
     {
       "name": "windows-clang-x64",
       "inherits": "windows-clang",
@@ -184,6 +190,10 @@
       "name": "windows-msvc-arm64",
       "configurePreset": "windows-msvc-arm64"
     },
+    {
+      "name": "windows-msvc-host",
+      "configurePreset": "windows-msvc-host"
+    },
     {
       "name": "windows-clang-x64",
       "configurePreset": "windows-clang-x64"