CC = arm-none-eabi-gcc

CFLAGS = -mcpu=cortex-m4 -mthumb -mfloat-abi=hard -mfpu=fpv4-sp-d16
CFLAGS += -Wall -Werror -Wpedantic -Wextra
# Remove unused code and data; https://gcc.gnu.org/onlinedocs/gnat_ugn/Compilation-options.html
CFLAGS += -ffunction-sections -fdata-sections
# Don't include memcpy
CFLAGS += -fno-builtin
# "-fno-common ... specifies that the compiler places uninitialized global variables in the BSS section of the object file."
CFLAGS += -fno-common

DEBUG ?= 1
ifeq ($(DEBUG), 0)
	# Optimize for size
	CFLAGS += -Os
else
	CFLAGS += -O0 -g3 -ggdb
endif

LDFLAGS = -T link.ld -nostartfiles -nostdlib --specs nano.specs -lc -lgcc -Wl,--gc-sections -Wl,-Map=$@.map

SRC_DIR = src
BUILD_DIR = build
TARGET = final

SRC_FILES := $(wildcard $(SRC_DIR)/*.c)
PREP_FILES := $(patsubst $(SRC_DIR)/%.c,$(BUILD_DIR)/%.i,$(SRC_FILES))
ASM_FILES := $(patsubst $(BUILD_DIR)/%.i,$(BUILD_DIR)/%.S,$(PREP_FILES))
OBJ_FILES := $(patsubst $(BUILD_DIR)/%.S,$(BUILD_DIR)/%.o,$(ASM_FILES))

.PHONY: build
build: builddir preprocess compile assemble $(BUILD_DIR)/$(TARGET).elf

$(BUILD_DIR)/$(TARGET).elf: $(OBJ_FILES)
	$(CC) $(LDFLAGS) $^ -o $@

$(BUILD_DIR)/%.i: $(SRC_DIR)/%.c
	$(CC) $(CFLAGS) -E $^ -o $@

$(BUILD_DIR)/%.S: $(BUILD_DIR)/%.i
	$(CC) $(CFLAGS) -S $^ -o $@

$(BUILD_DIR)/%.o: $(BUILD_DIR)/%.S
	$(CC) $(CFLAGS) -c $^ -o $@

.PHONY: builddir
builddir:
	mkdir $(BUILD_DIR)

.PHONY: preprocess
preprocess: $(PREP_FILES)

.PHONY: compile
compile: preprocess $(ASM_FILES)

.PHONY: assemble
assemble: compile $(OBJ_FILES)

.PHONY: clean
clean:
	rm -rf $(BUILD_DIR)