Support host builds using clang toolchain (#2798)

This PR adds the `CLANG_BUILD` for host builds. The toolchain detection logic is in the main build.mk file as there might be future support for clang toolchains for actual devices. It's also a revision to the existing logic which checks GCC compiler version.

Try it out using `make SMING_SOC=host CLANG_BUILD=1`.
To build with a specific (installed) version of clang, for example clang-15, use `CLANG_BUILD=15` .
Further customisation can be made by editing `Sming/Arch/Host/build.mk`.

Clang-tidy support (#2648) is also improved as there are some compiler flag differences between GCC and clang which are now shared between CLANG_TIDY and CLANG_BUILD operation.

An extra CI build has been added using clang.

Further to #2773, the default toolchain for macos is a version of clang (Apple Clang). This PR doesn't quite support that because there are other issues to address, but it's a step in the right direction.

.github/workflows/ci.yml

@@ -13,11 +13,16 @@ jobs:
       matrix:
         os: [ubuntu-latest, windows-latest]
         variant: [esp8266, host, rp2040]
+        toolchain: [gcc]
         include:
           - variant: esp8266
             arch: Esp8266
           - variant: host
             arch: Host
+          - os: ubuntu-latest
+            variant: host
+            arch: Host
+            toolchain: clang
           - variant: rp2040
             arch: Rp2040
 
@@ -30,6 +35,7 @@ jobs:
     env:
       SMING_ARCH: ${{ matrix.arch }}
       SMING_SOC: ${{ matrix.variant }}
+      CLANG_BUILD: ${{ matrix.toolchain == 'clang' && '15' || '0' }}
 
     steps:
     - name: Fix autocrlf setting

.github/workflows/library.yml

@@ -24,11 +24,16 @@ jobs:
         os: [ubuntu-latest, windows-latest]
         variant: [esp8266, host, esp32, esp32s2, esp32c3, esp32s3, esp32c2, rp2040]
         idf_version: ["4.4", ""] # "" denotes default, currently 5.2
+        toolchain: [gcc]
         include:
           - variant: esp8266
             arch: Esp8266
           - variant: host
             arch: Host
+          - os: ubuntu-latest
+            variant: host
+            arch: Host
+            toolchain: clang
           - variant: esp32
             arch: Esp32
           - variant: esp32s2
@@ -61,6 +66,7 @@ jobs:
       SMING_ARCH: ${{ matrix.arch }}
       SMING_SOC: ${{ matrix.variant }}
       INSTALL_IDF_VER: ${{ matrix.idf_version }}
+      CLANG_BUILD: ${{ matrix.toolchain == 'clang' && '15' || '0' }}
 
     steps:
     - name: Fix autocrlf setting

Sming/Arch/Host/README.rst

@@ -25,6 +25,9 @@ Ensure you are using relatively recent compilers, with 32-bit libraries availabl
 For Linux, you may require the ``gcc-multilib`` and ``g++-multilib``
 packages to build 32-bit executables on a 64-bit OS.
 
+MacOS comes pre-installed with ``Apple Clang`` as the standard toolchain.
+This should be sufficient to build Sming in Host mode.
+
 For Windows, make sure your ``MinGW`` distro is up to date.
 See :doc:`/getting-started/windows/index` for further details.
 
@@ -58,6 +61,16 @@ Configuration
 
    Note: These settings are not 'sticky'
 
+
+.. envvar:: CLANG_BUILD
+
+   0: Use GCC (default)
+   1: Use standard ``clang``
+   N: Use specific installed version, ``clang-N``
+
+   Note: This setting is not 'sticky'
+
+
 Components
 ----------
 

Sming/Arch/Host/build.mk

@@ -8,6 +8,25 @@ CPPFLAGS	+= -DARCH_HOST
 
 TOOLSPEC 	:=
 
+ifndef CLANG_BUILD
+override CLANG_BUILD := 0
+endif
+
+ifneq ($(CLANG_BUILD),0)
+ifeq ($(CLANG_BUILD),1)
+CLANG_VER :=
+else
+CLANG_VER := -$(CLANG_BUILD)
+endif
+AS		:= $(TOOLSPEC)clang$(CLANG_VER)
+CC		:= $(TOOLSPEC)clang$(CLANG_VER)
+CXX		:= $(TOOLSPEC)clang++$(CLANG_VER)
+AR		:= $(TOOLSPEC)ar
+LD		:= $(TOOLSPEC)clang++$(CLANG_VER)
+NM		:= $(TOOLSPEC)nm
+OBJCOPY		:= $(TOOLSPEC)objcopy
+OBJDUMP		:= $(TOOLSPEC)objdump
+else
 AS		:= $(TOOLSPEC)gcc
 CC		:= $(TOOLSPEC)gcc
 CXX		:= $(TOOLSPEC)g++
@@ -16,6 +35,8 @@ LD		:= $(TOOLSPEC)g++
 NM		:= $(TOOLSPEC)nm
 OBJCOPY		:= $(TOOLSPEC)objcopy
 OBJDUMP		:= $(TOOLSPEC)objdump
+endif
+
 GDB		:= $(TOOLSPEC)gdb
 
 GCC_UPGRADE_URL := https://sming.readthedocs.io/en/latest/arch/host/host-emulator.html\#c-c-32-bit-compiler-and-libraries

Sming/build.mk

@@ -30,6 +30,7 @@ ifdef CLANG_TIDY
 ifneq (Host,$(SMING_ARCH))
   $(error CLANG_TIDY supported only for Host architecture.)
 endif
+USE_CLANG := 1
 endif
 
 export SMING_ARCH
@@ -157,18 +158,10 @@ endif
 
 # Common C/C++ flags passed to user libraries
 CPPFLAGS = \
-	-Wl,-EL \
 	-finline-functions \
 	-fdata-sections \
 	-ffunction-sections \
-	-D_POSIX_C_SOURCE=200809L
-
-# Required to access peripheral registers using structs
-# e.g. `uint32_t value: 8` sitting at a byte or word boundary will be 'optimised' to
-# an 8-bit fetch/store instruction which will not work; it must be a full 32-bit access.
-CPPFLAGS += -fstrict-volatile-bitfields
-
-CPPFLAGS += \
+	-D_POSIX_C_SOURCE=200809L \
 	-Wall \
 	-Wpointer-arith \
 	-Wno-comment \
@@ -216,9 +209,41 @@ include $(ARCH_BASE)/build.mk
 
 ifndef MAKE_CLEAN
 
-# Detect compiler version
-DEBUG_VARS			+= GCC_VERSION
-GCC_VERSION			:= $(shell $(CC) -dumpversion)
+# Detect compiler version and name
+DEBUG_VARS				+= COMPILER_VERSION_FULL COMPILER_VERSION COMPILER_NAME
+COMPILER_VERSION_FULL	:= $(shell $(CC) -v 2>&1 | $(AWK) -F " version " '/ version /{ a=$$1; gsub(/ +/, "-", a); print a, $$2}')
+COMPILER_NAME			:= $(word 1,$(COMPILER_VERSION_FULL))
+COMPILER_VERSION		:= $(word 2,$(COMPILER_VERSION_FULL))
+
+ifndef USE_CLANG
+# Required to access peripheral registers using structs
+# e.g. `uint32_t value: 8` sitting at a byte or word boundary will be 'optimised' to
+# an 8-bit fetch/store instruction which will not work; it must be a full 32-bit access.
+ifeq ($(COMPILER_NAME),gcc)
+CPPFLAGS += -fstrict-volatile-bitfields
+COMPILER_VERSION_MIN := 8
+else
+ifeq (,$(findstring clang,$(COMPILER_NAME)))
+$(error Compiler '$(COMPILER_VERSION_FULL)' not recognised. Please install GCC tools.)
+endif
+COMPILER_VERSION_MIN := 15
+ifndef COMPILER_NOTICE_PRINTED
+$(info Note: Building with $(COMPILER_NAME) $(COMPILER_VERSION).)
+COMPILER_NOTICE_PRINTED := 1
+endif
+USE_CLANG := 1
+endif
+endif
+
+ifdef USE_CLANG
+CPPFLAGS += \
+	-Wno-vla-extension \
+	-Wno-unused-private-field \
+	-Wno-bitfield-constant-conversion \
+	-Wno-unknown-pragmas \
+	-Wno-initializer-overrides
+endif
+
 
 # Use c11 by default. Every architecture can override it
 DEBUG_VARS			+= SMING_C_STD
@@ -227,21 +252,17 @@ CFLAGS				+= -std=$(SMING_C_STD)
 
 # Select C++17 if supported, defaulting to C++11 otherwise
 DEBUG_VARS			+= SMING_CXX_STD
-ifeq ($(GCC_VERSION),4.8.5)
-SMING_CXX_STD		?= c++11
-else
 SMING_CXX_STD		?= c++17
-endif
 CXXFLAGS			+= -std=$(SMING_CXX_STD)
 
-GCC_MIN_MAJOR_VERSION := 8
-GCC_VERSION_COMPATIBLE := $(shell expr $$(echo $(GCC_VERSION) | cut -f1 -d.) \>= $(GCC_MIN_MAJOR_VERSION))
+COMPILER_VERSION_MAJOR := $(firstword $(subst ., ,$(COMPILER_VERSION)))
+COMPILER_VERSION_COMPATIBLE := $(shell expr $(COMPILER_VERSION_MAJOR) \>= $(COMPILER_VERSION_MIN))
 
-ifeq ($(GCC_VERSION_COMPATIBLE),0)
+ifeq ($(COMPILER_VERSION_COMPATIBLE),0)
 ifneq ($(GCC_UPGRADE_URL),)
 $(info Instructions for upgrading your compiler can be found here: $(GCC_UPGRADE_URL))
 endif
-$(error Please, upgrade your GCC compiler to version $(GCC_MIN_MAJOR_VERSION) or newer.)
+$(error Please upgrade your compiler to $(COMPILER_NAME) $(COMPILER_VERSION_MIN) or newer)
 endif
 endif
 

Sming/component-wrapper.mk

@@ -120,10 +120,6 @@ endif
 # Additional flags to pass to clang
 CLANG_FLAG_EXTRA ?=
 
-# Flags which clang doesn't recognise
-CLANG_FLAG_UNKNOWN := \
-	-fstrict-volatile-bitfields
-
 # $1 -> absolute source directory, no trailing path separator
 # $2 -> relative output build directory, with trailing path separator
 define GenerateCompileTargets
@@ -142,7 +138,7 @@ ifneq (,$(filter $1/%.c,$(SOURCE_FILES)))
 ifdef CLANG_TIDY
 $2%.o: $1/%.c
 	$(vecho) "TIDY $$<"
-	$(Q) $(CLANG_TIDY) $$< -- $(addprefix -I,$(INCDIR)) $$(filter-out $(CLANG_FLAG_UNKNOWN),$(CPPFLAGS) $(CFLAGS)) $(CLANG_FLAG_EXTRA)
+	$(Q) $(CLANG_TIDY) $$< -- $(addprefix -I,$(INCDIR)) $(CPPFLAGS) $(CFLAGS) $(CLANG_FLAG_EXTRA)
 else
 $2%.o: $1/%.c $2%.c.d
 	$(vecho) "CC $$<"
@@ -156,7 +152,7 @@ ifneq (,$(filter $1/%.cpp,$(SOURCE_FILES)))
 ifdef CLANG_TIDY
 $2%.o: $1/%.cpp
 	$(vecho) "TIDY $$<"
-	$(Q) $(CLANG_TIDY) $$< -- $(addprefix -I,$(INCDIR)) $$(filter-out $(CLANG_FLAG_UNKNOWN),$(CPPFLAGS) $(CXXFLAGS)) $(CLANG_FLAG_EXTRA)
+	$(Q) $(CLANG_TIDY) $$< -- $(addprefix -I,$(INCDIR)) $(CPPFLAGS) $(CXXFLAGS) $(CLANG_FLAG_EXTRA)
 else
 $2%.o: $1/%.cpp $2%.cpp.d
 	$(vecho) "C+ $$<"

Sming/project.mk

@@ -100,6 +100,7 @@ LIBS				:= $(EXTRA_LIBS)
 
 # Common linker flags
 LDFLAGS = \
+	-Wl,-EL \
 	-Wl,--gc-sections \
 	-Wl,-Map=$(basename $@).map
 

samples/Basic_Ota/app/application.cpp

@@ -218,14 +218,14 @@ void handleCommand(const String& str)
 void serialCallBack(Stream& stream, char arrivedChar, unsigned short availableCharsCount)
 {
 	switch(commandBuffer.process(stream, Serial)) {
-	case commandBuffer.Action::submit:
+	case LineBufferBase::Action::submit:
 		if(commandBuffer) {
 			handleCommand(String(commandBuffer));
 			commandBuffer.clear();
 		}
 		showPrompt();
 		break;
-	case commandBuffer.Action::clear:
+	case LineBufferBase::Action::clear:
 		showPrompt();
 		break;
 	default:;

samples/LiveDebug/app/application.cpp

@@ -123,10 +123,10 @@ void onDataReceived(Stream& source, char arrivedChar, unsigned short availableCh
 	}
 
 	switch(commandBuffer.process(source, Serial)) {
-	case commandBuffer.Action::clear:
+	case LineBufferBase::Action::clear:
 		showPrompt();
 		break;
-	case commandBuffer.Action::submit: {
+	case LineBufferBase::Action::submit: {
 		if(commandBuffer) {
 			handleCommand(String(commandBuffer));
 			commandBuffer.clear();