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https://github.com/RIOT-OS/RIOT.git
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6dcd3bb8ff
clang/LLVM is a bit more finicky with what target triples it accepts compared to GCC. However, the GCC target triple is needed to properly locate the C libraries. In case a locally installed GCC toolchain uses a technically not fully correct target triple, it might be impossible to build with LLVM. The solution here is to allow specifying a TARGET_ARCH_LLVM target triple (which defaults to TARGET_ARCH), which is passed to clang. For locating the C lib, still TARGET_ARCH is used.
93 lines
3.4 KiB
Makefile
93 lines
3.4 KiB
Makefile
LLVMPREFIX ?= llvm-
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# Apple XCode doesn't prefix its tools with llvm-, but manually installed LLVM
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# on OSX might have the llvm- prefix, we can't simply test against uname -s.
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# Test if llvm-ar exists
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ifeq (,$(shell command -v $(LLVMPREFIX)ar 2>/dev/null))
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# fall back to system tools
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LLVMPREFIX :=
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endif
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CC = clang
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CXX = clang++
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CCAS ?= $(CC)
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AS = $(LLVMPREFIX)as
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AR = $(LLVMPREFIX)ar
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NM = $(LLVMPREFIX)nm
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# LLVM does have a linker, however, it is not entirely
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# compatible with GCC. For instance spec files as used in
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# `makefiles/libc/newlib.mk` are not supported. Therefore
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# we just use GCC for now.
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LINK = $(PREFIX)gcc
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LINKXX = $(PREFIX)g++
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# objcopy does not have a clear substitute in LLVM, use GNU binutils
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# OBJCOPY = $(LLVMPREFIX)objcopy
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_OBJCOPY := $(shell command -v $(PREFIX)objcopy || command -v gobjcopy || command -v objcopy)
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OBJCOPY ?= $(_OBJCOPY)
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ifeq ($(OBJCOPY),)
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$(warning objcopy not found. Hex file will not be created.)
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OBJCOPY = true
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endif
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# Default to the native (g)objdump, helps when using toolchain from docker
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_OBJDUMP := $(or $(shell command -v $(LLVMPREFIX)objdump || command -v gobjdump),objdump)
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OBJDUMP ?= $(_OBJDUMP)
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SIZE = $(LLVMPREFIX)size
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# LLVM lacks a binutils strip tool as well...
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#export STRIP = $(LLVMPREFIX)strip
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# We use GDB for debugging for now, maybe LLDB will be supported in the future.
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include $(RIOTMAKE)/tools/gdb.inc.mk
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# Include directories from gcc
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# $1: language <c|cpp>
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#
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# `realpath` is used instead of `abspath` to support Mingw32 which has issues
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# with windows formatted gcc directories
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#
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# CFLAGS_CPU is used to get the correct multilib include header.
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gcc_include_dirs = $(realpath \
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$(shell $(PREFIX)gcc $(CFLAGS_CPU) -v -x $1 -E /dev/null 2>&1 | \
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sed \
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-e '1,/\#include <...> search starts here:/d' \
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-e '/End of search list./,$$d' \
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-e 's/^ *//')\
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)
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ifneq (,$(TARGET_ARCH))
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TARGET_ARCH_LLVM ?= $(TARGET_ARCH)
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ifeq (,$(CFLAGS_CPU))
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$(error CFLAGS_CPU must have been defined to use `llvm`.)
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endif
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# Tell clang to cross compile
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CFLAGS += -target $(TARGET_ARCH_LLVM)
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CXXFLAGS += -target $(TARGET_ARCH_LLVM)
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# We currently don't use LLVM for linking (see comment above).
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# LINKFLAGS += -target $(TARGET_ARCH_LLVM)
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# Clang on Linux uses GCC's C and C++ headers and libstdc++ (installed with GCC)
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# Extract include directories from GCC
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GCC_C_INCLUDE_DIRS = $(call gcc_include_dirs,c)
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GCC_CXX_INCLUDE_DIRS = $(call gcc_include_dirs,c++)
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GCC_C_INCLUDES = $(addprefix -isystem ,$(GCC_C_INCLUDE_DIRS))
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GCC_CXX_INCLUDES = $(addprefix -isystem ,$(GCC_CXX_INCLUDE_DIRS))
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INCLUDES += $(GCC_C_INCLUDES)
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CXXINCLUDES += $(GCC_CXX_INCLUDES)
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endif
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# For bare metal targets the performance penalty of atomic operations being
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# implemented with library calls is totally insignificant. In case LTO is
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# is enabled, the overhead compared to manually disabling interrupts is fully
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# optimized out (unless atomic operations could be grouped together to a single
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# critical section). So there is - in our use case - no value in having the
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# warning
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CFLAGS += -Wno-atomic-alignment
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# For compatibility with older clang versions we also disable warnings on
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# unsupported warning flags:
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CFLAGS += -Wno-unknown-warning-option
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OPTIONAL_CFLAGS_BLACKLIST += -fno-delete-null-pointer-checks
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OPTIONAL_CFLAGS_BLACKLIST += -Wformat-overflow
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OPTIONAL_CFLAGS_BLACKLIST += -Wformat-truncation
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