export GDBPREFIX  ?= $(PREFIX)
export LLVMPREFIX ?= llvm-
export CC          = clang
export CXX         = clang++
export LINK        = $(CC)
export AS          = $(LLVMPREFIX)as
export AR          = $(LLVMPREFIX)ar
export NM          = $(LLVMPREFIX)nm
# There is no LLVM linker yet, use GNU binutils.
#export LINKER      = $(LLVMPREFIX)ld
# objcopy does not have a clear substitute in LLVM, use GNU binutils
#export OBJCOPY     = $(LLVMPREFIX)objcopy
export OBJCOPY     = $(PREFIX)objcopy
export OBJDUMP     = $(LLVMPREFIX)objdump
export SIZE        = $(LLVMPREFIX)size
export DBG         = $(GDBPREFIX)gdb
# LLVM lacks a binutils strip tool as well...
#export STRIP      = $(LLVMPREFIX)strip

# Clang on Linux uses GCC's C++ headers and libstdc++ (installed with GCC)
# Ubuntu and Debian use /etc/alternatives/gcc-$(TARGET_ARCH)-include/c++/$(GCC_VERSION)
# Arch uses /usr/$(TARGET_ARCH)/include/c++/$(GCC_VERSION)
# Gentoo uses /usr/lib/gcc/$(TARGET_ARCH)/$(GCC_VERSION)/include/g++-v5
GCC_CXX_INCLUDE_PATTERNS ?= \
  /etc/alternatives/gcc-$(TARGET_ARCH)-include/c++/*/ \
  /usr/$(TARGET_ARCH)/include/c++/*/ \
  /usr/lib/gcc/$(TARGET_ARCH)/*/include/g++-v5 \
  #

# Try to find the proper multilib directory using GCC, this may fail if a cross-
# GCC is not installed.
ifeq ($(GCC_MULTI_DIR),)
  GCC_MULTI_DIR := $(shell $(PREFIX)gcc -print-multi-directory $(CFLAGS) 2>/dev/null)
endif

# Tell clang to cross compile
export CFLAGS     += -target $(TARGET_ARCH)
export CXXFLAGS   += -target $(TARGET_ARCH)
export LINKFLAGS  += -target $(TARGET_ARCH)

# Use the wildcard Makefile function to search for existing directories matching
# the patterns above. We use the -isystem gcc/clang argument to add the include
# directories as system include directories, which means they will not be
# searched until after all the project specific include directories (-I/path)
# We sort the list of found directories and take the last one, it will likely be
# the most recent GCC version. This avoids using old headers left over from
# previous tool chain installations.
GCC_CXX_INCLUDES ?= \
    $(addprefix \
        -isystem $(lastword $(sort \
            $(foreach pat, $(GCC_CXX_INCLUDE_PATTERNS), $(wildcard $(pat))))), \
        /. /$(TARGET_ARCH)/$(GCC_MULTI_DIR) /backward \
    )

export INCLUDES += $(GCC_CXX_INCLUDES)