Conditional Compilation in Makefile

makefile

Solution

If you are using GNU make then you can use directives such as `if` and similar.

See Conditional Parts of Makefiles in the documentation.

If you case you could do it like this:

C_SRC +=  \
CMSIS/CM3/CoreSupport/core_cm3.c \
....
led.c \
trace.c

ifeq ($(SPECIAL),"")
C_SRC += main.c
else
C_SRC += main_special.c
endif

The when calling `make` on the command line, if you set the variable `SPECIAL` then the file `main_special.c` will be used, otherwise `main.c` will be used.

Command line for using `main_special.c`:

$ make SPECIAL=1

Problem

I currently have a make file, part of which looks like the following. ``` #################################################################### # Files # #################################################################### C_SRC += \ CMSIS/CM3/CoreSupport/core_cm3.c \ CMSIS/CM3/DeviceSupport/EnergyMicro/EFM32/system_efm32.c \ efm32lib/src/efm32_assert.c \ efm32lib/src/efm32_system.c \ efm32lib/src/efm32_gpio.c \ efm32lib/src/efm32_cmu.c \ efm32lib/src/efm32_usart.c \ efm32lib/src/efm32_i2c.c \ efm32lib/src/efm32_dma.c \ efm32lib/src/efm32_timer.c \ efm32lib/src/efm32_int.c \ efm32lib/src/efm32_emu.c \ efm32lib/src/efm32_adc.c \ efm32lib/src/efm32_rtc.c \ radio.c \ led.c \ trace.c \ main.c S_SRC += \ CMSIS/CM3/DeviceSupport/EnergyMicro/EFM32/startup/cs3/startup_efm32.s #################################################################### # Rules # #################################################################### C_FILES = $(notdir $(C_SRC) ) S_FILES = $(notdir $(S_SRC) ) #make list of source paths, sort also removes duplicates C_PATHS = $(sort $(dir $(C_SRC) ) ) S_PATHS = $(sort $(dir $(S_SRC) ) ) C_OBJS = $(addprefix $(OBJ_DIR)/, $(C_FILES:.c=.o)) S_OBJS = $(addprefix $(OBJ_DIR)/, $(S_FILES:.s=.o)) C_DEPS = $(addprefix $(OBJ_DIR)/, $(C_FILES:.c=.d)) vpath %.c $(C_PATHS) vpath %.s $(S_PATHS) # Default build is debug build all: debug debug: CFLAGS += -DDEBUG -O0 -g3 debug: $(OBJ_DIR) $(LST_DIR) $(EXE_DIR) $(EXE_DIR)/$(PROJECTNAME).bin release: CFLAGS += -DNDEBUG -O3 release: $(OBJ_DIR) $(LST_DIR) $(EXE_DIR) $(EXE_DIR)/$(PROJECTNAME).bin base: CFLAGS += -DDEBUG -O0 -g3 base: $(OBJ_DIR) $(LST_DIR) $(EXE_DIR) $(EXE_DIR)/$(PROJECTNAME).bin ``` Essentially what I want to do is if it is run with the base target then I want to change the main.c file in `C_SRC` with mainbase.c I have tried for hours and hours now and have gotten no where with it. Any advice? Thanks!

Original source