Merge pull request #2606 from hathach/build-clang

Add  Clang support

33 files changed, 366 insertions, 237 deletions

diff --git a/examples/build_system/cmake/cpu/cortex-m0.cmake b/examples/build_system/cmake/cpu/cortex-m0.cmake
index bc2257048..62019d90d 100644
--- a/examples/build_system/cmake/cpu/cortex-m0.cmake
+++ b/examples/build_system/cmake/cpu/cortex-m0.cmake
@@ -4,14 +4,19 @@ if (TOOLCHAIN STREQUAL "gcc")
     -mcpu=cortex-m0plus
     -mfloat-abi=soft
     )
+  set(FREERTOS_PORT GCC_ARM_CM0 CACHE INTERNAL "")
 
+elseif (TOOLCHAIN STREQUAL "clang")
+  set(TOOLCHAIN_COMMON_FLAGS
+    --target=arm-none-eabi
+    -mcpu=cortex-m0
+    )
   set(FREERTOS_PORT GCC_ARM_CM0 CACHE INTERNAL "")
 
 elseif (TOOLCHAIN STREQUAL "iar")
   set(TOOLCHAIN_COMMON_FLAGS
     --cpu cortex-m0
     )
-
   set(FREERTOS_PORT IAR_ARM_CM0 CACHE INTERNAL "")
 
 endif ()
diff --git a/examples/build_system/cmake/cpu/cortex-m0plus.cmake b/examples/build_system/cmake/cpu/cortex-m0plus.cmake
index bc2257048..ddf0f16af 100644
--- a/examples/build_system/cmake/cpu/cortex-m0plus.cmake
+++ b/examples/build_system/cmake/cpu/cortex-m0plus.cmake
@@ -4,14 +4,19 @@ if (TOOLCHAIN STREQUAL "gcc")
     -mcpu=cortex-m0plus
     -mfloat-abi=soft
     )
+  set(FREERTOS_PORT GCC_ARM_CM0 CACHE INTERNAL "")
 
+elseif (TOOLCHAIN STREQUAL "clang")
+  set(TOOLCHAIN_COMMON_FLAGS
+    --target=arm-none-eabi
+    -mcpu=cortex-m0plus
+    )
   set(FREERTOS_PORT GCC_ARM_CM0 CACHE INTERNAL "")
 
 elseif (TOOLCHAIN STREQUAL "iar")
   set(TOOLCHAIN_COMMON_FLAGS
     --cpu cortex-m0
     )
-
   set(FREERTOS_PORT IAR_ARM_CM0 CACHE INTERNAL "")
 
 endif ()
diff --git a/examples/build_system/cmake/cpu/cortex-m23.cmake b/examples/build_system/cmake/cpu/cortex-m23.cmake
index c7ce1d242..00382ed9b 100644
--- a/examples/build_system/cmake/cpu/cortex-m23.cmake
+++ b/examples/build_system/cmake/cpu/cortex-m23.cmake
@@ -4,14 +4,19 @@ if (TOOLCHAIN STREQUAL "gcc")
     -mcpu=cortex-m23
     -mfloat-abi=soft
     )
+  set(FREERTOS_PORT GCC_ARM_CM23_NTZ_NONSECURE CACHE INTERNAL "")
 
+elseif (TOOLCHAIN STREQUAL "clang")
+  set(TOOLCHAIN_COMMON_FLAGS
+    --target=arm-none-eabi
+    -mcpu=cortex-m23
+    )
   set(FREERTOS_PORT GCC_ARM_CM23_NTZ_NONSECURE CACHE INTERNAL "")
 
 elseif (TOOLCHAIN STREQUAL "iar")
   set(TOOLCHAIN_COMMON_FLAGS
     --cpu cortex-m23
     )
-
   set(FREERTOS_PORT IAR_ARM_CM23_NTZ_NONSECURE CACHE INTERNAL "")
 
 endif ()
diff --git a/examples/build_system/cmake/cpu/cortex-m3.cmake b/examples/build_system/cmake/cpu/cortex-m3.cmake
index f6f5a62f8..27888604e 100644
--- a/examples/build_system/cmake/cpu/cortex-m3.cmake
+++ b/examples/build_system/cmake/cpu/cortex-m3.cmake
@@ -3,14 +3,19 @@ if (TOOLCHAIN STREQUAL "gcc")
     -mthumb
     -mcpu=cortex-m3
     )
+  set(FREERTOS_PORT GCC_ARM_CM3 CACHE INTERNAL "")
 
+elseif (TOOLCHAIN STREQUAL "clang")
+  set(TOOLCHAIN_COMMON_FLAGS
+    --target=arm-none-eabi
+    -mcpu=cortex-m3
+    )
   set(FREERTOS_PORT GCC_ARM_CM3 CACHE INTERNAL "")
 
 elseif (TOOLCHAIN STREQUAL "iar")
   set(TOOLCHAIN_COMMON_FLAGS
     --cpu cortex-m3
     )
-
   set(FREERTOS_PORT IAR_ARM_CM3 CACHE INTERNAL "")
 
 endif ()
diff --git a/examples/build_system/cmake/cpu/cortex-m33-nodsp-nofp.cmake b/examples/build_system/cmake/cpu/cortex-m33-nodsp-nofp.cmake
index 01e6b979a..51fd70b0e 100644
--- a/examples/build_system/cmake/cpu/cortex-m33-nodsp-nofp.cmake
+++ b/examples/build_system/cmake/cpu/cortex-m33-nodsp-nofp.cmake
@@ -4,14 +4,15 @@ if (TOOLCHAIN STREQUAL "gcc")
     -mcpu=cortex-m33+nodsp
     -mfloat-abi=soft
     )
-
   set(FREERTOS_PORT GCC_ARM_CM33_NTZ_NONSECURE CACHE INTERNAL "")
 
+elseif (TOOLCHAIN STREQUAL "clang")
+  message(FATAL_ERROR "Clang is not supported for this target")
+
 elseif (TOOLCHAIN STREQUAL "iar")
   set(TOOLCHAIN_COMMON_FLAGS
     --cpu cortex-m33+nodsp
     )
-
   set(FREERTOS_PORT IAR_ARM_CM33_NTZ_NONSECURE CACHE INTERNAL "")
 
 endif ()
diff --git a/examples/build_system/cmake/cpu/cortex-m33.cmake b/examples/build_system/cmake/cpu/cortex-m33.cmake
index 94c29099d..d56d07ebc 100644
--- a/examples/build_system/cmake/cpu/cortex-m33.cmake
+++ b/examples/build_system/cmake/cpu/cortex-m33.cmake
@@ -5,7 +5,14 @@ if (TOOLCHAIN STREQUAL "gcc")
     -mfloat-abi=hard
     -mfpu=fpv5-sp-d16
     )
+  set(FREERTOS_PORT GCC_ARM_CM33_NTZ_NONSECURE CACHE INTERNAL "")
 
+elseif (TOOLCHAIN STREQUAL "clang")
+  set(TOOLCHAIN_COMMON_FLAGS
+    --target=arm-none-eabi
+    -mcpu=cortex-m33
+    -mfpu=fpv5-sp-d16
+    )
   set(FREERTOS_PORT GCC_ARM_CM33_NTZ_NONSECURE CACHE INTERNAL "")
 
 elseif (TOOLCHAIN STREQUAL "iar")
@@ -13,7 +20,6 @@ elseif (TOOLCHAIN STREQUAL "iar")
     --cpu cortex-m33
     --fpu VFPv5-SP
     )
-
   set(FREERTOS_PORT IAR_ARM_CM33_NTZ_NONSECURE CACHE INTERNAL "")
 
 endif ()
diff --git a/examples/build_system/cmake/cpu/cortex-m4.cmake b/examples/build_system/cmake/cpu/cortex-m4.cmake
index db308aa83..9cdadc6f8 100644
--- a/examples/build_system/cmake/cpu/cortex-m4.cmake
+++ b/examples/build_system/cmake/cpu/cortex-m4.cmake
@@ -5,7 +5,16 @@ if (TOOLCHAIN STREQUAL "gcc")
     -mfloat-abi=hard
     -mfpu=fpv4-sp-d16
     )
+  if (NOT DEFINED FREERTOS_PORT)
+    set(FREERTOS_PORT GCC_ARM_CM4F CACHE INTERNAL "")
+  endif ()
 
+elseif (TOOLCHAIN STREQUAL "clang")
+  set(TOOLCHAIN_COMMON_FLAGS
+    --target=arm-none-eabi
+    -mcpu=cortex-m4
+    -mfpu=fpv4-sp-d16
+    )
   if (NOT DEFINED FREERTOS_PORT)
     set(FREERTOS_PORT GCC_ARM_CM4F CACHE INTERNAL "")
   endif ()
diff --git a/examples/build_system/cmake/cpu/cortex-m7.cmake b/examples/build_system/cmake/cpu/cortex-m7.cmake
index 3e5f7f44b..b41dfded5 100644
--- a/examples/build_system/cmake/cpu/cortex-m7.cmake
+++ b/examples/build_system/cmake/cpu/cortex-m7.cmake
@@ -5,7 +5,14 @@ if (TOOLCHAIN STREQUAL "gcc")
     -mfloat-abi=hard
     -mfpu=fpv5-d16
     )
+  set(FREERTOS_PORT GCC_ARM_CM7 CACHE INTERNAL "")
 
+elseif (TOOLCHAIN STREQUAL "clang")
+  set(TOOLCHAIN_COMMON_FLAGS
+    --target=arm-none-eabi
+    -mcpu=cortex-m7
+    -mfpu=fpv5-d16
+    )
   set(FREERTOS_PORT GCC_ARM_CM7 CACHE INTERNAL "")
 
 elseif (TOOLCHAIN STREQUAL "iar")
@@ -13,7 +20,6 @@ elseif (TOOLCHAIN STREQUAL "iar")
     --cpu cortex-m7
     --fpu VFPv5_D16
     )
-
   set(FREERTOS_PORT IAR_ARM_CM7 CACHE INTERNAL "")
 
 endif ()
diff --git a/examples/build_system/cmake/cpu/msp430.cmake b/examples/build_system/cmake/cpu/msp430.cmake
index b4b47a2e8..584ec5741 100644
--- a/examples/build_system/cmake/cpu/msp430.cmake
+++ b/examples/build_system/cmake/cpu/msp430.cmake
@@ -1,6 +1,9 @@
 if (TOOLCHAIN STREQUAL "gcc")
   set(FREERTOS_PORT GCC_MSP430F449 CACHE INTERNAL "")
 
+elseif (TOOLCHAIN STREQUAL "clang")
+  message(FATAL_ERROR "Clang is not supported for this target")
+
 elseif (TOOLCHAIN STREQUAL "iar")
   set(FREERTOS_PORT IAR_MSP430 CACHE INTERNAL "")
 
diff --git a/examples/build_system/cmake/toolchain/arm_clang.cmake b/examples/build_system/cmake/toolchain/arm_clang.cmake
new file mode 100644
index 000000000..754d672fd
--- /dev/null
+++ b/examples/build_system/cmake/toolchain/arm_clang.cmake
@@ -0,0 +1,21 @@
+if (NOT DEFINED CMAKE_C_COMPILER)
+  set(CMAKE_C_COMPILER "clang")
+endif ()
+
+if (NOT DEFINED CMAKE_CXX_COMPILER)
+  set(CMAKE_CXX_COMPILER "clang++")
+endif ()
+
+set(CMAKE_ASM_COMPILER ${CMAKE_C_COMPILER})
+set(CMAKE_SIZE "llvm-size" CACHE FILEPATH "")
+set(CMAKE_OBJCOPY "llvm-objcopy" CACHE FILEPATH "")
+set(CMAKE_OBJDUMP "llvm-objdump" CACHE FILEPATH "")
+
+include(${CMAKE_CURRENT_LIST_DIR}/common.cmake)
+
+get_property(IS_IN_TRY_COMPILE GLOBAL PROPERTY IN_TRY_COMPILE)
+if (IS_IN_TRY_COMPILE)
+  set(CMAKE_C_LINK_FLAGS "${CMAKE_C_LINK_FLAGS} -nostdlib")
+  set(CMAKE_CXX_LINK_FLAGS "${CMAKE_CXX_LINK_FLAGS} -nostdlib")
+  cmake_print_variables(CMAKE_C_LINK_FLAGS)
+endif ()
diff --git a/examples/build_system/cmake/toolchain/arm_gcc.cmake b/examples/build_system/cmake/toolchain/arm_gcc.cmake
index d3fd5b557..d3d73c629 100644
--- a/examples/build_system/cmake/toolchain/arm_gcc.cmake
+++ b/examples/build_system/cmake/toolchain/arm_gcc.cmake
@@ -1,5 +1,3 @@
-set(CMAKE_SYSTEM_NAME Generic)
-
 if (NOT DEFINED CMAKE_C_COMPILER)
   set(CMAKE_C_COMPILER "arm-none-eabi-gcc")
 endif ()
@@ -9,44 +7,15 @@ if (NOT DEFINED CMAKE_CXX_COMPILER)
 endif ()
 
 set(CMAKE_ASM_COMPILER ${CMAKE_C_COMPILER})
-
 set(CMAKE_SIZE "arm-none-eabi-size" CACHE FILEPATH "")
 set(CMAKE_OBJCOPY "arm-none-eabi-objcopy" CACHE FILEPATH "")
 set(CMAKE_OBJDUMP "arm-none-eabi-objdump" CACHE FILEPATH "")
 
-set_property(GLOBAL PROPERTY TARGET_SUPPORTS_SHARED_LIBS FALSE)
-
-# Look for includes and libraries only in the target system prefix.
-set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
-set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
-set(CMAKE_FIND_ROOT_PATH_MODE_PACKAGE ONLY)
-set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
-
-# pass TOOLCHAIN_CPU to
-set(CMAKE_TRY_COMPILE_PLATFORM_VARIABLES CMAKE_SYSTEM_PROCESSOR)
-
-include(${CMAKE_CURRENT_LIST_DIR}/../cpu/${CMAKE_SYSTEM_PROCESSOR}.cmake)
-
-# enable all possible warnings for building examples
-list(APPEND TOOLCHAIN_COMMON_FLAGS
-  -fdata-sections
-  -ffunction-sections
-  -fsingle-precision-constant
-  -fno-strict-aliasing
-  )
-
-list(APPEND TOOLCHAIN_EXE_LINKER_FLAGS
-  -Wl,--print-memory-usage
-  -Wl,--gc-sections
-  -Wl,--cref
-  )
-
-include(${CMAKE_CURRENT_LIST_DIR}/set_flags.cmake)
+include(${CMAKE_CURRENT_LIST_DIR}/common.cmake)
 
-# try_compile is cmake test compiling its own example,
-# pass -nostdlib to skip stdlib linking
 get_property(IS_IN_TRY_COMPILE GLOBAL PROPERTY IN_TRY_COMPILE)
 if (IS_IN_TRY_COMPILE)
   set(CMAKE_C_LINK_FLAGS "${CMAKE_C_LINK_FLAGS} -nostdlib")
   set(CMAKE_CXX_LINK_FLAGS "${CMAKE_CXX_LINK_FLAGS} -nostdlib")
+  cmake_print_variables(CMAKE_C_LINK_FLAGS)
 endif ()
diff --git a/examples/build_system/cmake/toolchain/arm_iar.cmake b/examples/build_system/cmake/toolchain/arm_iar.cmake
index 1482624e5..6d2219ca8 100644
--- a/examples/build_system/cmake/toolchain/arm_iar.cmake
+++ b/examples/build_system/cmake/toolchain/arm_iar.cmake
@@ -1,32 +1,17 @@
-set(CMAKE_SYSTEM_NAME Generic)
+if (NOT DEFINED CMAKE_C_COMPILER)
+  set(CMAKE_C_COMPILER "iccarm")
+endif()
 
-set(CMAKE_C_COMPILER "iccarm")
-set(CMAKE_CXX_COMPILER "iccarm")
-set(CMAKE_ASM_COMPILER "iasmarm")
+if (NOT DEFINED CMAKE_CXX_COMPILER)
+  set(CMAKE_CXX_COMPILER "iccarm")
+endif()
+
+if (NOT DEFINED CMAKE_ASM_COMPILER)
+  set(CMAKE_ASM_COMPILER "iasmarm")
+endif()
 
 set(CMAKE_SIZE "size" CACHE FILEPATH "")
 set(CMAKE_OBJCOPY "ielftool" CACHE FILEPATH "")
 set(CMAKE_OBJDUMP "iefdumparm" CACHE FILEPATH "")
 
-set_property(GLOBAL PROPERTY TARGET_SUPPORTS_SHARED_LIBS FALSE)
-
-# Look for includes and libraries only in the target system prefix.
-set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
-set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
-set(CMAKE_FIND_ROOT_PATH_MODE_PACKAGE ONLY)
-set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
-
-# pass TOOLCHAIN_CPU to
-set(CMAKE_TRY_COMPILE_PLATFORM_VARIABLES CMAKE_SYSTEM_PROCESSOR)
-
-include(${CMAKE_CURRENT_LIST_DIR}/../cpu/${CMAKE_SYSTEM_PROCESSOR}.cmake)
-
-# enable all possible warnings for building examples
-list(APPEND TOOLCHAIN_COMMON_FLAGS
-  )
-
-list(APPEND TOOLCHAIN_EXE_LINKER_FLAGS
-  --diag_suppress=Li065
-  )
-
-include(${CMAKE_CURRENT_LIST_DIR}/set_flags.cmake)
+include(${CMAKE_CURRENT_LIST_DIR}/common.cmake)
diff --git a/examples/build_system/cmake/toolchain/common.cmake b/examples/build_system/cmake/toolchain/common.cmake
new file mode 100644
index 000000000..688715914
--- /dev/null
+++ b/examples/build_system/cmake/toolchain/common.cmake
@@ -0,0 +1,64 @@
+include(CMakePrintHelpers)
+
+# ----------------------------------------------------------------------------
+# Common
+# ----------------------------------------------------------------------------
+set(CMAKE_SYSTEM_NAME Generic)
+set_property(GLOBAL PROPERTY TARGET_SUPPORTS_SHARED_LIBS FALSE)
+
+# Look for includes and libraries only in the target system prefix.
+set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
+set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
+set(CMAKE_FIND_ROOT_PATH_MODE_PACKAGE ONLY)
+set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
+
+# pass TOOLCHAIN_CPU to
+set(CMAKE_TRY_COMPILE_PLATFORM_VARIABLES CMAKE_SYSTEM_PROCESSOR)
+include(${CMAKE_CURRENT_LIST_DIR}/../cpu/${CMAKE_SYSTEM_PROCESSOR}.cmake)
+
+# ----------------------------------------------------------------------------
+# Compile flags
+# ----------------------------------------------------------------------------
+if (TOOLCHAIN STREQUAL "gcc")
+  list(APPEND TOOLCHAIN_COMMON_FLAGS
+    -fdata-sections
+    -ffunction-sections
+    -fsingle-precision-constant
+    -fno-strict-aliasing
+    )
+  list(APPEND TOOLCHAIN_EXE_LINKER_FLAGS
+    -Wl,--print-memory-usage
+    -Wl,--gc-sections
+    -Wl,--cref
+    )
+
+elseif (TOOLCHAIN STREQUAL "iar")
+  #list(APPEND TOOLCHAIN_COMMON_FLAGS)
+  list(APPEND TOOLCHAIN_EXE_LINKER_FLAGS
+    --diag_suppress=Li065
+    )
+
+elseif (TOOLCHAIN STREQUAL "clang")
+  list(APPEND TOOLCHAIN_COMMON_FLAGS
+    -fdata-sections
+    -ffunction-sections
+    -fno-strict-aliasing
+    )
+  list(APPEND TOOLCHAIN_EXE_LINKER_FLAGS
+    -Wl,--print-memory-usage
+    -Wl,--gc-sections
+    -Wl,--cref
+    )
+endif ()
+
+# join the toolchain flags into a single string
+list(JOIN TOOLCHAIN_COMMON_FLAGS " " TOOLCHAIN_COMMON_FLAGS)
+foreach (LANG IN ITEMS C CXX ASM)
+  set(CMAKE_${LANG}_FLAGS_INIT ${TOOLCHAIN_COMMON_FLAGS})
+  # optimization flags for LOG, LOGGER ?
+  #set(CMAKE_${LANG}_FLAGS_RELEASE_INIT "-Os")
+  #set(CMAKE_${LANG}_FLAGS_DEBUG_INIT "-O0")
+endforeach ()
+
+# Linker
+list(JOIN TOOLCHAIN_EXE_LINKER_FLAGS " " CMAKE_EXE_LINKER_FLAGS_INIT)
diff --git a/examples/build_system/cmake/toolchain/msp430_gcc.cmake b/examples/build_system/cmake/toolchain/msp430_gcc.cmake
index 6291ce5a4..73368adba 100644
--- a/examples/build_system/cmake/toolchain/msp430_gcc.cmake
+++ b/examples/build_system/cmake/toolchain/msp430_gcc.cmake
@@ -1,5 +1,3 @@
-set(CMAKE_SYSTEM_NAME Generic)
-
 if (NOT DEFINED CMAKE_C_COMPILER)
   set(CMAKE_C_COMPILER "msp430-elf-gcc")
 endif ()
@@ -14,39 +12,4 @@ set(CMAKE_SIZE "msp430-elf-size" CACHE FILEPATH "")
 set(CMAKE_OBJCOPY "msp430-elf-objcopy" CACHE FILEPATH "")
 set(CMAKE_OBJDUMP "msp430-elf-objdump" CACHE FILEPATH "")
 
-set_property(GLOBAL PROPERTY TARGET_SUPPORTS_SHARED_LIBS FALSE)
-
-# Look for includes and libraries only in the target system prefix.
-set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
-set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
-set(CMAKE_FIND_ROOT_PATH_MODE_PACKAGE ONLY)
-set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
-
-# pass TOOLCHAIN_CPU to
-set(CMAKE_TRY_COMPILE_PLATFORM_VARIABLES CMAKE_SYSTEM_PROCESSOR)
-
-include(${CMAKE_CURRENT_LIST_DIR}/../cpu/${CMAKE_SYSTEM_PROCESSOR}.cmake)
-
-# enable all possible warnings for building examples
-list(APPEND TOOLCHAIN_COMMON_FLAGS
-  -fdata-sections
-  -ffunction-sections
-  -fsingle-precision-constant
-  -fno-strict-aliasing
-  )
-
-list(APPEND TOOLCHAIN_EXE_LINKER_FLAGS
-  -Wl,--print-memory-usage
-  -Wl,--gc-sections
-  -Wl,--cref
-  )
-
-include(${CMAKE_CURRENT_LIST_DIR}/set_flags.cmake)
-
-# try_compile is cmake test compiling its own example,
-# pass -nostdlib to skip stdlib linking
-get_property(IS_IN_TRY_COMPILE GLOBAL PROPERTY IN_TRY_COMPILE)
-if (IS_IN_TRY_COMPILE)
-  set(CMAKE_C_LINK_FLAGS "${CMAKE_C_LINK_FLAGS} -nostdlib")
-  set(CMAKE_CXX_LINK_FLAGS "${CMAKE_CXX_LINK_FLAGS} -nostdlib")
-endif ()
+include(${CMAKE_CURRENT_LIST_DIR}/common.cmake)
diff --git a/examples/build_system/cmake/toolchain/set_flags.cmake b/examples/build_system/cmake/toolchain/set_flags.cmake
deleted file mode 100644
index 44930ef4d..000000000
--- a/examples/build_system/cmake/toolchain/set_flags.cmake
+++ /dev/null
@@ -1,17 +0,0 @@
-include(CMakePrintHelpers)
-
-# join the toolchain flags into a single string
-list(JOIN TOOLCHAIN_COMMON_FLAGS " " TOOLCHAIN_COMMON_FLAGS)
-
-foreach (LANG IN ITEMS C CXX ASM)
-  set(CMAKE_${LANG}_FLAGS_INIT ${TOOLCHAIN_COMMON_FLAGS})
-
-  #cmake_print_variables(CMAKE_${LANG}_FLAGS_INIT)
-
-  # optimization flags for LOG, LOGGER ?
-  #set(CMAKE_${LANG}_FLAGS_RELEASE_INIT "-Os")
-  #set(CMAKE_${LANG}_FLAGS_DEBUG_INIT "-O0")
-endforeach ()
-
-# Linker
-list(JOIN TOOLCHAIN_EXE_LINKER_FLAGS " " CMAKE_EXE_LINKER_FLAGS_INIT)
diff --git a/examples/build_system/make/cpu/cortex-m0.mk b/examples/build_system/make/cpu/cortex-m0.mk
index feb0f395b..c2c33a2ee 100644
--- a/examples/build_system/make/cpu/cortex-m0.mk
+++ b/examples/build_system/make/cpu/cortex-m0.mk
@@ -4,10 +4,18 @@ ifeq ($(TOOLCHAIN),gcc)
     -mcpu=cortex-m0 \
     -mfloat-abi=soft \
 
+else ifeq ($(TOOLCHAIN),clang)
+  CFLAGS += \
+	  --target=arm-none-eabi \
+	  -mcpu=cortex-m0 \
+
 else ifeq ($(TOOLCHAIN),iar)
   # IAR Flags
   CFLAGS += --cpu cortex-m0
   ASFLAGS += --cpu cortex-m0
+
+else
+  $(error "TOOLCHAIN is not supported")
 endif
 
 # For freeRTOS port source
diff --git a/examples/build_system/make/cpu/cortex-m0plus.mk b/examples/build_system/make/cpu/cortex-m0plus.mk
index b416b7a4a..fe8feb227 100644
--- a/examples/build_system/make/cpu/cortex-m0plus.mk
+++ b/examples/build_system/make/cpu/cortex-m0plus.mk
@@ -4,10 +4,18 @@ ifeq ($(TOOLCHAIN),gcc)
     -mcpu=cortex-m0plus \
     -mfloat-abi=soft \
 
+else ifeq ($(TOOLCHAIN),clang)
+  CFLAGS += \
+	  --target=arm-none-eabi \
+	  -mcpu=cortex-m0plus \
+
 else ifeq ($(TOOLCHAIN),iar)
   # IAR Flags
   CFLAGS += --cpu cortex-m0+
   ASFLAGS += --cpu cortex-m0+
+
+else
+  $(error "TOOLCHAIN is not supported")
 endif
 
 # For freeRTOS port source
diff --git a/examples/build_system/make/cpu/cortex-m23.mk b/examples/build_system/make/cpu/cortex-m23.mk
index 29542d8e8..7ab758352 100644
--- a/examples/build_system/make/cpu/cortex-m23.mk
+++ b/examples/build_system/make/cpu/cortex-m23.mk
@@ -4,10 +4,18 @@ ifeq ($(TOOLCHAIN),gcc)
     -mcpu=cortex-m23 \
     -mfloat-abi=soft \
 
+else ifeq ($(TOOLCHAIN),clang)
+  CFLAGS += \
+	  --target=arm-none-eabi \
+	  -mcpu=cortex-m23 \
+
 else ifeq ($(TOOLCHAIN),iar)
   # IAR Flags
   CFLAGS += --cpu cortex-m23
   ASFLAGS += --cpu cortex-m23
+
+else
+  $(error "TOOLCHAIN is not supported")
 endif
 
 # For freeRTOS port source
diff --git a/examples/build_system/make/cpu/cortex-m3.mk b/examples/build_system/make/cpu/cortex-m3.mk
index 7a34b9e04..b6325313f 100644
--- a/examples/build_system/make/cpu/cortex-m3.mk
+++ b/examples/build_system/make/cpu/cortex-m3.mk
@@ -4,13 +4,18 @@ ifeq ($(TOOLCHAIN),gcc)
     -mcpu=cortex-m3 \
     -mfloat-abi=soft \
 
+else ifeq ($(TOOLCHAIN),clang)
+  CFLAGS += \
+	  --target=arm-none-eabi \
+	  -mcpu=cortex-m3 \
+
 else ifeq ($(TOOLCHAIN),iar)
   # IAR Flags
-  CFLAGS += \
-    --cpu cortex-m3 \
+  CFLAGS += --cpu cortex-m3
+  ASFLAGS += --cpu cortex-m3
 
-  ASFLAGS += \
-     --cpu cortex-m3
+else
+  $(error "TOOLCHAIN is not supported")
 endif
 
 # For freeRTOS port source
diff --git a/examples/build_system/make/cpu/cortex-m33-nodsp-nofp.mk b/examples/build_system/make/cpu/cortex-m33-nodsp-nofp.mk
index c65f24376..405053dd0 100644
--- a/examples/build_system/make/cpu/cortex-m33-nodsp-nofp.mk
+++ b/examples/build_system/make/cpu/cortex-m33-nodsp-nofp.mk
@@ -1,16 +1,24 @@
 ifeq ($(TOOLCHAIN),gcc)
-	CFLAGS += \
+  CFLAGS += \
 	-mthumb \
 	-mcpu=cortex-m33+nodsp \
 	-mfloat-abi=soft \
 
+else ifeq ($(TOOLCHAIN),clang)
+  CFLAGS += \
+	  --target=arm-none-eabi \
+	  -mcpu=cortex-m33 \
+	  -mfpu=softvp \
+
 else ifeq ($(TOOLCHAIN),iar)
-	CFLAGS += \
+  CFLAGS += \
 		--cpu cortex-m33+nodsp \
 
-	ASFLAGS += \
+  ASFLAGS += \
 		--cpu cortex-m33+nodsp \
 
+else
+  $(error "TOOLCHAIN is not supported")
 endif
 
 FREERTOS_PORTABLE_SRC ?= $(FREERTOS_PORTABLE_PATH)/ARM_CM33_NTZ/non_secure
diff --git a/examples/build_system/make/cpu/cortex-m33.mk b/examples/build_system/make/cpu/cortex-m33.mk
index fe5b7b380..47b0eaecd 100644
--- a/examples/build_system/make/cpu/cortex-m33.mk
+++ b/examples/build_system/make/cpu/cortex-m33.mk
@@ -5,15 +5,23 @@ ifeq ($(TOOLCHAIN),gcc)
     -mfloat-abi=hard \
     -mfpu=fpv5-sp-d16 \
 
+else ifeq ($(TOOLCHAIN),clang)
+  CFLAGS += \
+	  --target=arm-none-eabi \
+	  -mcpu=cortex-m33 \
+	  -mfpu=fpv5-sp-d16 \
+
 else ifeq ($(TOOLCHAIN),iar)
-	CFLAGS += \
+  CFLAGS += \
 		--cpu cortex-m33 \
 		--fpu VFPv5-SP \
 
-	ASFLAGS += \
+  ASFLAGS += \
 		--cpu cortex-m33 \
 		--fpu VFPv5-SP \
 
+else
+  $(error "TOOLCHAIN is not supported")
 endif
 
 FREERTOS_PORTABLE_SRC ?= $(FREERTOS_PORTABLE_PATH)/ARM_CM33_NTZ/non_secure
diff --git a/examples/build_system/make/cpu/cortex-m4.mk b/examples/build_system/make/cpu/cortex-m4.mk
index d8776b5d8..4e16819d1 100644
--- a/examples/build_system/make/cpu/cortex-m4.mk
+++ b/examples/build_system/make/cpu/cortex-m4.mk
@@ -5,9 +5,18 @@ ifeq ($(TOOLCHAIN),gcc)
     -mfloat-abi=hard \
     -mfpu=fpv4-sp-d16 \
 
+else ifeq ($(TOOLCHAIN),clang)
+  CFLAGS += \
+	  --target=arm-none-eabi \
+	  -mcpu=cortex-m4 \
+	  -mfpu=fpv4-sp-d16 \
+
 else ifeq ($(TOOLCHAIN),iar)
   CFLAGS += --cpu cortex-m4 --fpu VFPv4
   ASFLAGS += --cpu cortex-m4 --fpu VFPv4
+
+else
+  $(error "TOOLCHAIN is not supported")
 endif
 
 FREERTOS_PORTABLE_SRC ?= $(FREERTOS_PORTABLE_PATH)/ARM_CM4F
diff --git a/examples/build_system/make/cpu/cortex-m7.mk b/examples/build_system/make/cpu/cortex-m7.mk
index 0e3461787..3e6116179 100644
--- a/examples/build_system/make/cpu/cortex-m7.mk
+++ b/examples/build_system/make/cpu/cortex-m7.mk
@@ -5,6 +5,12 @@ ifeq ($(TOOLCHAIN),gcc)
     -mfloat-abi=hard \
     -mfpu=fpv5-d16 \
 
+else ifeq ($(TOOLCHAIN),clang)
+  CFLAGS += \
+	  --target=arm-none-eabi \
+	  -mcpu=cortex-m7 \
+	  -mfpu=fpv5-d16 \
+
 else ifeq ($(TOOLCHAIN),iar)
   CFLAGS += \
   	--cpu cortex-m7 \
@@ -14,6 +20,8 @@ else ifeq ($(TOOLCHAIN),iar)
 		--cpu cortex-m7 \
 		--fpu VFPv5_D16 \
 
+else
+  $(error "TOOLCHAIN is not supported")
 endif
 
 FREERTOS_PORTABLE_SRC ?= $(FREERTOS_PORTABLE_PATH)/ARM_CM7/r0p1
diff --git a/examples/build_system/make/cpu/msp430.mk b/examples/build_system/make/cpu/msp430.mk
index 06340d23b..6daa2c38d 100644
--- a/examples/build_system/make/cpu/msp430.mk
+++ b/examples/build_system/make/cpu/msp430.mk
@@ -1,7 +1,11 @@
 ifeq ($(TOOLCHAIN),gcc)
   # nothing to add
+else ifeq ($(TOOLCHAIN),clang)
+  # nothing to add
 else ifeq ($(TOOLCHAIN),iar)
   # nothing to add
+else
+  $(error "TOOLCHAIN is not supported")
 endif
 
 # For freeRTOS port source
diff --git a/examples/build_system/make/make.mk b/examples/build_system/make/make.mk
index 772befca4..a78f4130d 100644
--- a/examples/build_system/make/make.mk
+++ b/examples/build_system/make/make.mk
@@ -2,6 +2,24 @@
 # Common make definition for all examples
 # ---------------------------------------
 
+#-------------------------------------------------------------
+# Toolchain
+# Can be changed via TOOLCHAIN=gcc|iar or CC=arm-none-eabi-gcc|iccarm|clang
+#-------------------------------------------------------------
+
+ifneq (,$(findstring clang,$(CC)))
+  TOOLCHAIN = clang
+else ifneq (,$(findstring iccarm,$(CC)))
+  TOOLCHAIN = iar
+else ifneq (,$(findstring gcc,$(CC)))
+  TOOLCHAIN = gcc
+endif
+
+# Default to GCC
+ifndef TOOLCHAIN
+  TOOLCHAIN = gcc
+endif
+
 #-------------- TOP and CURRENT_PATH ------------
 
 # Set TOP to be the path to get from the current directory (where make was invoked) to the top of the tree.
@@ -15,6 +33,8 @@ TOP = $(abspath $(subst make.mk,../../..,$(THIS_MAKEFILE)))
 # Set CURRENT_PATH to the relative path from TOP to the current directory, ie examples/device/cdc_msc_freertos
 CURRENT_PATH = $(subst $(TOP)/,,$(abspath .))
 
+#-------------- Linux/Windows ------------
+
 # Detect whether shell style is windows or not
 # https://stackoverflow.com/questions/714100/os-detecting-makefile/52062069#52062069
 ifeq '$(findstring ;,$(PATH))' ';'
@@ -26,13 +46,18 @@ CMDEXE := 1
 SHELL := cmd.exe
 endif
 
-# Handy check parameter function
-check_defined = \
-    $(strip $(foreach 1,$1, \
-    $(call __check_defined,$1,$(strip $(value 2)))))
-__check_defined = \
-    $(if $(value $1),, \
-    $(error Undefined make flag: $1$(if $2, ($2))))
+ifeq ($(CMDEXE),1)
+  CP = copy
+  RM = del
+  MKDIR = mkdir
+  PYTHON = python
+else
+  CP = cp
+  RM = rm
+  MKDIR = mkdir
+  PYTHON = python3
+endif
+
 
 # Build directory
 BUILD := _build/$(BOARD)
@@ -44,8 +69,8 @@ BIN := $(TOP)/_bin/$(BOARD)/$(notdir $(CURDIR))
 
 # Board without family
 ifneq ($(wildcard $(TOP)/hw/bsp/$(BOARD)/board.mk),)
-BOARD_PATH := hw/bsp/$(BOARD)
-FAMILY :=
+  BOARD_PATH := hw/bsp/$(BOARD)
+  FAMILY :=
 endif
 
 # Board within family
@@ -68,31 +93,6 @@ else
   SRC_C += $(subst $(TOP)/,,$(wildcard $(TOP)/$(FAMILY_PATH)/*.c))
 endif
 
-#-------------- Toolchain  ------------
-
-# Supported toolchain: gcc, iar
-TOOLCHAIN ?= gcc
-
-# Can be set by board, default to ARM GCC
-CROSS_COMPILE ?= arm-none-eabi-
-
-ifeq ($(TOOLCHAIN),iar)
-CC := iccarm
-USE_IAR = 1
-endif
-
-ifeq ($(CMDEXE),1)
-  CP = copy
-  RM = del
-  MKDIR = mkdir
-  PYTHON = python
-else
-  CP = cp
-  RM = rm
-  MKDIR = mkdir
-  PYTHON = python3
-endif
-
 #-------------- Source files and compiler flags --------------
 # tinyusb makefile
 include $(TOP)/src/tinyusb.mk
@@ -124,7 +124,7 @@ endif
 
 # Logger: default is uart, can be set to rtt or swo
 ifneq ($(LOGGER),)
-	CMAKE_DEFSYM +=	-DLOGGER=$(LOGGER)
+  CMAKE_DEFSYM +=	-DLOGGER=$(LOGGER)
 endif
 
 ifeq ($(LOGGER),rtt)
@@ -143,3 +143,11 @@ endif
 
 # toolchain specific
 include ${TOP}/examples/build_system/make/toolchain/arm_$(TOOLCHAIN).mk
+
+# Handy check parameter function
+check_defined = \
+    $(strip $(foreach 1,$1, \
+    $(call __check_defined,$1,$(strip $(value 2)))))
+__check_defined = \
+    $(if $(value $1),, \
+    $(error Undefined make flag: $1$(if $2, ($2))))
diff --git a/examples/build_system/make/rules.mk b/examples/build_system/make/rules.mk
index 78fce49d2..7b6b339ed 100644
--- a/examples/build_system/make/rules.mk
+++ b/examples/build_system/make/rules.mk
@@ -24,7 +24,7 @@ vpath %.c . $(TOP)
 vpath %.s . $(TOP)
 vpath %.S . $(TOP)
 
-include ${TOP}/examples/build_system/make/toolchain/arm_$(TOOLCHAIN)_rules.mk
+include ${TOP}/examples/build_system/make/toolchain/$(TOOLCHAIN)_rules.mk
 
 # ---------------------------------------
 # Compiler Flags
diff --git a/examples/build_system/make/toolchain/arm_clang.mk b/examples/build_system/make/toolchain/arm_clang.mk
new file mode 100644
index 000000000..97face39c
--- /dev/null
+++ b/examples/build_system/make/toolchain/arm_clang.mk
@@ -0,0 +1,10 @@
+CC = clang
+CXX = clang++
+AS = $(CC) -x assembler-with-cpp
+LD = $(CC)
+
+GDB = $(CROSS_COMPILE)gdb
+OBJCOPY = llvm-objcopy
+SIZE = llvm-size
+
+include ${TOP}/examples/build_system/make/toolchain/gcc_common.mk
diff --git a/examples/build_system/make/toolchain/arm_gcc.mk b/examples/build_system/make/toolchain/arm_gcc.mk
index ed5ddc970..a8576f8ee 100644
--- a/examples/build_system/make/toolchain/arm_gcc.mk
+++ b/examples/build_system/make/toolchain/arm_gcc.mk
@@ -1,5 +1,8 @@
 # makefile for arm gcc toolchain
 
+# Can be set by family, default to ARM GCC
+CROSS_COMPILE ?= arm-none-eabi-
+
 CC = $(CROSS_COMPILE)gcc
 CXX = $(CROSS_COMPILE)g++
 AS = $(CC) -x assembler-with-cpp
@@ -9,73 +12,9 @@ GDB = $(CROSS_COMPILE)gdb
 OBJCOPY = $(CROSS_COMPILE)objcopy
 SIZE = $(CROSS_COMPILE)size
 
-CC_VERSION := $(shell $(CC) -dumpversion)
-CC_VERSION_MAJOR = $(firstword $(subst ., ,$(CC_VERSION)))
-
-# ---------------------------------------
-# Compiler Flags
-# ---------------------------------------
 CFLAGS += \
-  -MD \
-  -ggdb \
-  -fdata-sections \
-  -ffunction-sections \
   -fsingle-precision-constant \
-  -fno-strict-aliasing \
-  -Wall \
-  -Wextra \
-  -Werror \
-  -Wfatal-errors \
-  -Wdouble-promotion \
-  -Wstrict-prototypes \
-  -Wstrict-overflow \
-  -Werror-implicit-function-declaration \
-  -Wfloat-equal \
-  -Wundef \
-  -Wshadow \
-  -Wwrite-strings \
-  -Wsign-compare \
-  -Wmissing-format-attribute \
-  -Wunreachable-code \
-  -Wcast-align \
-  -Wcast-function-type \
-  -Wcast-qual \
-  -Wnull-dereference \
-  -Wuninitialized \
-  -Wunused \
-  -Wreturn-type \
-  -Wredundant-decls \
-
-# conversion is too strict for most mcu driver, may be disable sign/int/arith-conversion
-#  -Wconversion
-
-# Size Optimization as default
-CFLAGS_OPTIMIZED ?= -Os
-
-# Debugging/Optimization
-ifeq ($(DEBUG), 1)
-  CFLAGS += -O0
-  NO_LTO = 1
-else
-  CFLAGS += $(CFLAGS_OPTIMIZED)
-endif
-
-# ---------------------------------------
-# Linker Flags
-# ---------------------------------------
-LDFLAGS += \
-  -Wl,[email protected] \
-  -Wl,-cref \
-  -Wl,-gc-sections \
 
-# renesas rx does not support --print-memory-usage flags
-ifneq ($(FAMILY),rx)
-LDFLAGS += -Wl,--print-memory-usage
-endif
+LIBS += -lgcc -lm -lnosys
 
-# from version 12
-ifeq ($(strip $(if $(CMDEXE),\
-               $(shell if $(CC_VERSION_MAJOR) geq 12 (echo 1) else (echo 0)),\
-               $(shell expr $(CC_VERSION_MAJOR) \>= 12))), 1)
-LDFLAGS += -Wl,--no-warn-rwx-segment
-endif
+include ${TOP}/examples/build_system/make/toolchain/gcc_common.mk
diff --git a/examples/build_system/make/toolchain/arm_iar.mk b/examples/build_system/make/toolchain/arm_iar.mk
index 04c9f22b3..17967b41a 100644
--- a/examples/build_system/make/toolchain/arm_iar.mk
+++ b/examples/build_system/make/toolchain/arm_iar.mk
@@ -1,4 +1,6 @@
 # makefile for arm iar toolchain
+
+CC = iccarm
 AS = iasmarm
 LD = ilinkarm
 OBJCOPY = ielftool --silent
diff --git a/examples/build_system/make/toolchain/clang_rules.mk b/examples/build_system/make/toolchain/clang_rules.mk
new file mode 100644
index 000000000..341f705b1
--- /dev/null
+++ b/examples/build_system/make/toolchain/clang_rules.mk
@@ -0,0 +1 @@
+include ${TOP}/examples/build_system/make/toolchain/gcc_rules.mk
diff --git a/examples/build_system/make/toolchain/gcc_common.mk b/examples/build_system/make/toolchain/gcc_common.mk
new file mode 100644
index 000000000..6986d8bba
--- /dev/null
+++ b/examples/build_system/make/toolchain/gcc_common.mk
@@ -0,0 +1,71 @@
+# ---------------------------------------
+# Compiler Flags
+# ---------------------------------------
+CFLAGS += \
+  -MD \
+  -ggdb \
+  -fdata-sections \
+  -ffunction-sections \
+  -fno-strict-aliasing \
+  -Wall \
+  -Wextra \
+  -Werror \
+  -Wfatal-errors \
+  -Wdouble-promotion \
+  -Wstrict-prototypes \
+  -Wstrict-overflow \
+  -Werror-implicit-function-declaration \
+  -Wfloat-equal \
+  -Wundef \
+  -Wshadow \
+  -Wwrite-strings \
+  -Wsign-compare \
+  -Wmissing-format-attribute \
+  -Wunreachable-code \
+  -Wcast-align \
+  -Wcast-function-type \
+  -Wcast-qual \
+  -Wnull-dereference \
+  -Wuninitialized \
+  -Wunused \
+  -Wreturn-type \
+  -Wredundant-decls \
+
+# conversion is too strict for most mcu driver, may be disable sign/int/arith-conversion
+#  -Wconversion
+
+# Size Optimization as default
+CFLAGS_OPTIMIZED ?= -Os
+
+# Debugging/Optimization
+ifeq ($(DEBUG), 1)
+  CFLAGS += -O0
+  NO_LTO = 1
+else
+  CFLAGS += $(CFLAGS_OPTIMIZED)
+endif
+
+# ---------------------------------------
+# Linker Flags
+# ---------------------------------------
+LDFLAGS += \
+  -Wl,[email protected] \
+  -Wl,--cref \
+  -Wl,-gc-sections \
+
+# renesas rx does not support --print-memory-usage flags
+ifneq ($(FAMILY),rx)
+LDFLAGS += -Wl,--print-memory-usage
+endif
+
+ifeq ($(TOOLCHAIN),gcc)
+CC_VERSION := $(shell $(CC) -dumpversion)
+CC_VERSION_MAJOR = $(firstword $(subst ., ,$(CC_VERSION)))
+
+# from version 12
+ifeq ($(strip $(if $(CMDEXE),\
+               $(shell if $(CC_VERSION_MAJOR) geq 12 (echo 1) else (echo 0)),\
+               $(shell expr $(CC_VERSION_MAJOR) \>= 12))), 1)
+LDFLAGS += -Wl,--no-warn-rwx-segment
+endif
+endif
diff --git a/examples/build_system/make/toolchain/arm_gcc_rules.mk b/examples/build_system/make/toolchain/gcc_rules.mk
index d295879d9..fc5225503 100644
--- a/examples/build_system/make/toolchain/arm_gcc_rules.mk
+++ b/examples/build_system/make/toolchain/gcc_rules.mk
@@ -21,8 +21,14 @@ ifneq ($(CFLAGS_SKIP),)
 CFLAGS := $(filter-out $(CFLAGS_SKIP),$(CFLAGS))
 endif
 
+ifeq ($(TOOLCHAIN),clang)
+CFLAGS += $(CFLAGS_CLANG)
+LDFLAGS += $(CFLAGS) $(LDFLAGS_CLANG)
+else
 LDFLAGS += $(CFLAGS) $(LDFLAGS_GCC)
+endif
 
+# TODO should be removed after all examples are updated
 ifdef LD_FILE
 LDFLAGS += -Wl,-T,$(TOP)/$(LD_FILE)
 endif
@@ -33,11 +39,7 @@ endif
 
 ASFLAGS += $(CFLAGS)
 
-LIBS_GCC ?= -lgcc -lm -lnosys
-
 # libc
-LIBS += $(LIBS_GCC)
-
 ifneq ($(BOARD), spresense)
 LIBS += -lc
 endif
diff --git a/examples/build_system/make/toolchain/arm_iar_rules.mk b/examples/build_system/make/toolchain/iar_rules.mk
index 2c066f6da..2c066f6da 100644
--- a/examples/build_system/make/toolchain/arm_iar_rules.mk
+++ b/examples/build_system/make/toolchain/iar_rules.mk