windows: add clang cross-compile support on Linux

cmake/Modules/CrossCompileWindows.cmake

@@ -113,18 +113,42 @@ function(setup_libftdi_windows)
         message(STATUS "Building libftdi for Windows...")
         file(MAKE_DIRECTORY ${LIBFTDI_BUILD_DIR})
 
+        set(LIBFTDI_CMAKE_ARGS
+            -DCMAKE_SYSTEM_NAME=Windows
+            -DCMAKE_C_COMPILER=${CMAKE_C_COMPILER}
+            -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}
+            -DCMAKE_INSTALL_PREFIX=${CROSS_DEPS_INSTALL_DIR}
+            -DCMAKE_PREFIX_PATH=${CROSS_DEPS_INSTALL_DIR}
+            -DLIBUSB_INCLUDE_DIRS=${CROSS_DEPS_INSTALL_DIR}/include/libusb-1.0
+            -DLIBUSB_LIBRARIES=${CROSS_DEPS_INSTALL_DIR}/lib/libusb-1.0.a
+            -DFTDIPP=OFF -DBUILD_TESTS=OFF -DDOCUMENTATION=OFF
+            -DEXAMPLES=OFF -DFTDI_EEPROM=OFF -DPYTHON_BINDINGS=OFF
+            -DSTATICLIBS=ON
+        )
+
+        if(CMAKE_RC_COMPILER)
+            list(APPEND LIBFTDI_CMAKE_ARGS -DCMAKE_RC_COMPILER=${CMAKE_RC_COMPILER})
+        endif()
+
+        foreach(_lang C CXX RC)
+            if(DEFINED CMAKE_${_lang}_COMPILER_TARGET AND NOT "${CMAKE_${_lang}_COMPILER_TARGET}" STREQUAL "")
+                list(APPEND LIBFTDI_CMAKE_ARGS "-DCMAKE_${_lang}_COMPILER_TARGET=${CMAKE_${_lang}_COMPILER_TARGET}")
+            endif()
+        endforeach()
+
+        foreach(_flags_var CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+            if(DEFINED ${_flags_var} AND NOT "${${_flags_var}}" STREQUAL "")
+                list(APPEND LIBFTDI_CMAKE_ARGS "-D${_flags_var}=${${_flags_var}}")
+            endif()
+        endforeach()
+
+        if(DEFINED CMAKE_SYSROOT AND NOT "${CMAKE_SYSROOT}" STREQUAL "")
+            list(APPEND LIBFTDI_CMAKE_ARGS -DCMAKE_SYSROOT=${CMAKE_SYSROOT})
+        endif()
+
         execute_process(
             COMMAND ${CMAKE_COMMAND}
-                -DCMAKE_SYSTEM_NAME=Windows
+                ${LIBFTDI_CMAKE_ARGS}
-                -DCMAKE_C_COMPILER=${CMAKE_C_COMPILER}
-                -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}
-                -DCMAKE_INSTALL_PREFIX=${CROSS_DEPS_INSTALL_DIR}
-                -DCMAKE_PREFIX_PATH=${CROSS_DEPS_INSTALL_DIR}
-                -DLIBUSB_INCLUDE_DIRS=${CROSS_DEPS_INSTALL_DIR}/include/libusb-1.0
-                -DLIBUSB_LIBRARIES=${CROSS_DEPS_INSTALL_DIR}/lib/libusb-1.0.a
-                -DFTDIPP=OFF -DBUILD_TESTS=OFF -DDOCUMENTATION=OFF
-                -DEXAMPLES=OFF -DFTDI_EEPROM=OFF -DPYTHON_BINDINGS=OFF
-                -DSTATICLIBS=ON
                 ${LIBFTDI_SRC_DIR}
             WORKING_DIRECTORY ${LIBFTDI_BUILD_DIR}
             RESULT_VARIABLE CONFIG_RESULT

cmake/Toolchain-x86_64-w64-mingw32-clang.cmake

@@ -0,0 +1,52 @@
+# CMake Toolchain file for cross-compiling to Windows x64 using Clang + MinGW-w64
+# Usage: cmake -DCMAKE_TOOLCHAIN_FILE=cmake/Toolchain-x86_64-w64-mingw32-clang.cmake ..
+
+set(CMAKE_SYSTEM_NAME Windows)
+set(CMAKE_SYSTEM_PROCESSOR x86_64)
+
+set(WINDOWS_TARGET_TRIPLE "x86_64-w64-mingw32")
+
+find_program(CMAKE_C_COMPILER NAMES clang)
+find_program(CMAKE_CXX_COMPILER NAMES clang++)
+find_program(CMAKE_RC_COMPILER NAMES llvm-rc x86_64-w64-mingw32-windres)
+
+if(NOT CMAKE_C_COMPILER OR NOT CMAKE_CXX_COMPILER)
+    message(FATAL_ERROR "clang/clang++ not found. Please install clang.")
+endif()
+
+set(CMAKE_C_COMPILER_TARGET ${WINDOWS_TARGET_TRIPLE})
+set(CMAKE_CXX_COMPILER_TARGET ${WINDOWS_TARGET_TRIPLE})
+
+if(CMAKE_RC_COMPILER AND CMAKE_RC_COMPILER MATCHES "llvm-rc$")
+    set(CMAKE_RC_COMPILER_TARGET ${WINDOWS_TARGET_TRIPLE})
+endif()
+
+# Keep target selection compatible with older CMake versions.
+set(CMAKE_C_FLAGS_INIT "--target=${WINDOWS_TARGET_TRIPLE}")
+set(CMAKE_CXX_FLAGS_INIT "--target=${WINDOWS_TARGET_TRIPLE}")
+
+option(CROSS_COMPILE_DEPS "Download and build Windows dependencies for cross-compilation" ON)
+
+set(CROSS_DEPS_DIR "${CMAKE_BINARY_DIR}/cross-deps" CACHE PATH "Directory for cross-compiled dependencies")
+
+if(EXISTS "/usr/x86_64-w64-mingw32/sys-root/mingw")
+    set(MINGW_SYSROOT "/usr/x86_64-w64-mingw32/sys-root/mingw")
+elseif(EXISTS "/usr/x86_64-w64-mingw32")
+    set(MINGW_SYSROOT "/usr/x86_64-w64-mingw32")
+else()
+    set(MINGW_SYSROOT "")
+endif()
+
+set(CMAKE_FIND_ROOT_PATH ${CROSS_DEPS_DIR} ${MINGW_SYSROOT})
+set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
+set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
+set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
+set(CMAKE_FIND_ROOT_PATH_MODE_PACKAGE ONLY)
+
+set(CMAKE_EXE_LINKER_FLAGS_INIT "-static -static-libgcc -static-libstdc++")
+
+set(ENABLE_UDEV OFF CACHE BOOL "" FORCE)
+set(ENABLE_LIBGPIOD OFF CACHE BOOL "" FORCE)
+set(ENABLE_REMOTEBITBANG OFF CACHE BOOL "" FORCE)
+set(ENABLE_XILINX_VIRTUAL_CABLE OFF CACHE BOOL "" FORCE)
+set(BUILD_STATIC ON CACHE BOOL "" FORCE)

doc/guide/install.rst

@@ -206,9 +206,9 @@ openFPGALoader can be installed via MSYS2:
 Cross-compilation from Linux
 ----------------------------
 
-openFPGALoader can be cross-compiled for Windows from Linux using MinGW-w64.
+openFPGALoader can be cross-compiled for Windows from Linux using MinGW-w64
-The build system will automatically download and build the required dependencies
+toolchains (GCC or Clang). The build system will automatically download and
-(libusb, libftdi).
+build the required dependencies (libusb, libftdi).
 
 **Prerequisites (Debian/Ubuntu):**
 
@@ -217,6 +217,8 @@ The build system will automatically download and build the required dependencies
     sudo apt install \
       mingw-w64 \
       libz-mingw-w64-dev \
+      clang \
+      lld \
       cmake \
       pkg-config \
       p7zip-full
@@ -230,11 +232,13 @@ The build system will automatically download and build the required dependencies
       mingw64-gcc-c++ \
       mingw64-zlib \
       mingw64-zlib-static \
+      clang \
+      lld \
       cmake \
       p7zip \
       p7zip-plugins
 
-**Build:**
+**Build (shared steps):**
 
 .. code-block:: bash
 
@@ -242,9 +246,21 @@ The build system will automatically download and build the required dependencies
     cd openFPGALoader
     mkdir build-win64
     cd build-win64
+
+**Configure + build with GCC (MinGW-w64):**
+
+.. code-block:: bash
+
     cmake -DCMAKE_TOOLCHAIN_FILE=../cmake/Toolchain-x86_64-w64-mingw32.cmake ..
     cmake --build . --parallel
 
+**Configure + build with Clang (MinGW-w64 target):**
+
+.. code-block:: bash
+
+    cmake -DCMAKE_TOOLCHAIN_FILE=../cmake/Toolchain-x86_64-w64-mingw32-clang.cmake ..
+    cmake --build . --parallel
+
 The resulting ``openFPGALoader.exe`` will be a statically-linked executable
 that only depends on standard Windows system DLLs (KERNEL32, msvcrt, WS2_32).
 
@@ -260,6 +276,8 @@ that only depends on standard Windows system DLLs (KERNEL32, msvcrt, WS2_32).
 .. code-block:: bash
 
     x86_64-w64-mingw32-strip openFPGALoader.exe
+    # or
+    llvm-strip openFPGALoader.exe
 
 **Cross-compilation options:**