SDK_ROOT          ?= ../..
GNU_INSTALL_ROOT  ?= $(SDK_ROOT)/tools/gcc-arm-none-eabi-10.3-2021.10
GNU_VERSION       ?= 10.3.1

RM                 = rm -rf

## Selecting Core
CORTEX_M           = 0

## Toolchain commands
GNU_PREFIX         = arm-none-eabi
CC                 = $(GNU_INSTALL_ROOT)/bin/$(GNU_PREFIX)-gcc
CXX                = $(GNU_INSTALL_ROOT)/bin/$(GNU_PREFIX)-c++
AS                 = $(GNU_INSTALL_ROOT)/bin/$(GNU_PREFIX)-as
AR                 = $(GNU_INSTALL_ROOT)/bin/$(GNU_PREFIX)-ar -r
LD                 = $(GNU_INSTALL_ROOT)/bin/$(GNU_PREFIX)-ld
NM                 = $(GNU_INSTALL_ROOT)/bin/$(GNU_PREFIX)-nm
OBJDUMP            = $(GNU_INSTALL_ROOT)/bin/$(GNU_PREFIX)-objdump
OBJCOPY            = $(GNU_INSTALL_ROOT)/bin/$(GNU_PREFIX)-objcopy
SIZE               = $(GNU_INSTALL_ROOT)/bin/$(GNU_PREFIX)-size
STRIP              = $(GNU_INSTALL_ROOT)/bin/$(GNU_PREFIX)-strip


## library file
LIBFILES          ?= -lc_nano -lgcc -lnosys

## library path
LIBDIR            += -L $(GNU_INSTALL_ROOT)/lib/gcc/arm-none-eabi/$(GNU_VERSION)/thumb/v6-m/nofp
LIBDIR            += -L $(GNU_INSTALL_ROOT)/arm-none-eabi/lib/thumb/v6-m/nofp
LIBDIR            += -L $(SDK_ROOT)/drivers/lib

## include
INC                = $(GNU_INSTALL_ROOT)/arm-none-eabi/include

## Options for specific architecture
CORE               = CM$(CORTEX_M)
ARCH_FLAGS         = -mthumb -mcpu=cortex-m$(CORTEX_M)

## Startup code & linker script
STARTUP           ?= $(SDK_ROOT)/core/gnu/startup.S
LINKER_SCRIPT     ?= $(SDK_ROOT)/core/gnu/link_xip.ld

# Optimization flags
OPT               ?= -Os -g

## C flags common to all targets
CFLAGS            += $(OPT)
CFLAGS            += $(ARCH_FLAGS)
# Generate .d file
#CFLAGS            += -MP -MD 
CFLAGS            += -std=gnu11
CFLAGS            += -Wall
#CFLAGS            += -Werror
# close all warning
#CFLAGS           += -w
CFLAGS            += -msoft-float
# keep every function in a separate section, this allows linker to discard unused ones
CFLAGS            += -ffunction-sections -fdata-sections -fno-strict-aliasing
CFLAGS            += -fno-builtin -fshort-enums

## Assembler flags common to all targets
ASMFLAGS          += $(ARCH_FLAGS)
# support ARM/Thumb interworking
ASMFLAGS          += -mthumb-interwork

## Linker flags
LDFLAGS           += $(OPT)
LDFLAGS           += -T$(LINKER_SCRIPT) -nostdlib -EL
# Remove unused sections (on some targets)
LDFLAGS           += --gc-sections
# Reduce code size by using target specific optimizations
LDFLAGS           += --relax
# cross reference table
LDFLAGS           += --cref