Fixing CMake 3.6 deprecation message

- CMake 3.6 finally adds proper cross-compiler detection
- When detected, use full compiler detection infrastructure
- Still maintains compatibility back to CMake 2.8 (at least for now)
- With new detection, selecting only the C compiler as it speeds up the CMake generaion process
- Added a GCC 4.9 minimum version requirement for Bootloader

Bootloader/CMakeLists.txt

@@ -103,7 +103,7 @@ include_directories (
 #
 
 #| Project
-project ( kiibohd_bootloader )
+project ( kiibohd_bootloader C )
 
 #| Target Name (output name)
 set ( TARGET kiibohd_bootloader )
@@ -113,6 +113,20 @@ cmake_minimum_required ( VERSION 2.8 )
 
 
 
+###
+# Minimum Compiler Version Checks
+#
+
+# Due to optimization requirements, we have to impose a minimum GCC version on the bootloader
+set ( BOOTLOADER_MIN_GCC_VERSION "4.9" )
+if ( "${CMAKE_C_COMPILER_ID}" STREQUAL "GNU" )
+	if ( CMAKE_C_COMPILER_VERSION VERSION_LESS "${BOOTLOADER_MIN_GCC_VERSION}" )
+		message( FATAL_ERROR "arm-none-eabi-gcc ${BOOTLOADER_MIN_GCC_VERSION} or higher is required for bootloader" )
+	endif ()
+endif ()
+
+
+
 ###
 # CMake Build Env
 #

CMakeLists.txt

@@ -38,8 +38,8 @@ set( CHIP
 #| clang does work though
 #| Currently only arm is supported with clang
 set( COMPILER
-	"gcc"   # arm-none-eabi-gcc / avr-gcc - Default
-#       "clang" # arm-none-eabi
+	"gcc"   # arm-none-eabi-gcc / avr-gcc / host-gcc - Default
+#       "clang" # arm-none-eabi / host
 	CACHE STRING "Compiler Type"
 )
 
@@ -48,7 +48,7 @@ set( COMPILER
 ###
 # Compiler Intialization
 #
-set ( CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} ${CMAKE_SOURCE_DIR}/Lib/CMake )
+set( CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} ${CMAKE_SOURCE_DIR}/Lib/CMake )
 include( initialize )
 
 
@@ -139,7 +139,7 @@ set( MAIN_SRCS
 #
 
 #| Project
-project( kiibohd_controller )
+project( kiibohd_controller C )
 
 #| Target Name (output name)
 set( TARGET kiibohd )

Lib/CMake/arm.cmake

@@ -10,22 +10,53 @@
 ###
 
 
+###
+# Compiler Check
+#
 
-#| Set the Compilers (must be set first)
-include( CMakeForceCompiler )
-message( STATUS "Compiler Selected:" )
-if ( "${COMPILER}" MATCHES "gcc" )
-	cmake_force_c_compiler  ( arm-none-eabi-gcc ARMCCompiler )
-	cmake_force_cxx_compiler( arm-none-eabi-g++ ARMCxxCompiler )
-	set( _CMAKE_TOOLCHAIN_PREFIX arm-none-eabi- )
-	message( "gcc" )
-elseif ( "${COMPILER}" MATCHES "clang" )
-	cmake_force_c_compiler  ( clang   ARMCCompiler )
-	cmake_force_cxx_compiler( clang++ ARMCxxCompiler )
-	set( _CMAKE_TOOLCHAIN_PREFIX llvm- )
-	message( "clang" )
+#|
+#| In CMake 3.6 a new feature to configure try_compile to work with cross-compilers
+#| https://cmake.org/cmake/help/v3.6/variable/CMAKE_TRY_COMPILE_TARGET_TYPE.html#variable:CMAKE_TRY_COMPILE_TARGET_TYPE
+#| If we detect CMake 3.6 or higher, use the new method
+#|
+if ( NOT CMAKE_VERSION VERSION_LESS "3.6" )
+	# Prepare for cross-compilation
+	set( CMAKE_TRY_COMPILE_TARGET_TYPE "STATIC_LIBRARY" )
+	set( CMAKE_SYSTEM_NAME "Generic" )
+
+	message( STATUS "Compiler Selected:" )
+	if ( "${COMPILER}" MATCHES "gcc" )
+		set( CMAKE_C_COMPILER   arm-none-eabi-gcc )
+		set( _CMAKE_TOOLCHAIN_PREFIX arm-none-eabi- )
+		message( "gcc" )
+	elseif ( "${COMPILER}" MATCHES "clang" )
+		set( CMAKE_C_COMPILER    clang )
+		set( CMAKE_C_COMPILER_ID ARMCCompiler )
+		set( _CMAKE_TOOLCHAIN_PREFIX llvm- )
+		message( "clang" )
+	else ()
+		message( AUTHOR_WARNING "COMPILER: ${COMPILER} - Unknown compiler selection" )
+	endif ()
+
+#|
+#| Before CMake 3.6 the cmake_force_c_compiler command was necessary to select cross-compilers
+#| and other problemmatic compilers.
+#|
 else ()
-	message( AUTHOR_WARNING "COMPILER: ${COMPILER} - Unknown compiler selection" )
+	# Set the Compilers (must be set first)
+	include( CMakeForceCompiler )
+	message( STATUS "Compiler Selected:" )
+	if ( "${COMPILER}" MATCHES "gcc" )
+		cmake_force_c_compiler( arm-none-eabi-gcc ARMCCompiler )
+		set( _CMAKE_TOOLCHAIN_PREFIX arm-none-eabi- )
+		message( "gcc" )
+	elseif ( "${COMPILER}" MATCHES "clang" )
+		cmake_force_c_compiler( clang ARMCCompiler )
+		set( _CMAKE_TOOLCHAIN_PREFIX llvm- )
+		message( "clang" )
+	else ()
+		message( AUTHOR_WARNING "COMPILER: ${COMPILER} - Unknown compiler selection" )
+	endif ()
 endif ()