How to add a library path to a makefile? - c

Question

I was making a makefile for cross-compilation between a host and arm based microcontroller. So how do I add a specific library to the recipe of the makefile?
include sources.mk
ifeq ($(PLATFORM),MSP432)
# Platform Overrides
# Architectures Specific Flags
LINKER_FILE = msp432p401r.lds
CPU = cortex-m4
ARCH = thumb
SPECS = nosys.specs
CPP = -mcpu=$(CPU) -m$(ARCH) --specs=$(SPECS) -DMSP432
# Compiler Flags and Defines
CC = arm-none-eabi-gcc
LD = arm-none-eabi-ld
endif
ifeq ($(PLATFORM),HOST)
CC = gcc
CPP= DHOST
endif
TARGET =c1m2
LDFLAGS = -Wl,-Map=$(TARGET).map -T $(LINKER_FILE)
CFLAGS = -Wall -Werror -g -O0 -$(CPP) -I/Desktop/ese-coursera-
course1/assessments/m2/include/common/platform.h
-std=c99
.PHONY: build
build: all
.PHONY: all
all: $(TARGET).out
.PHONY: clean
clean:
rm -f $(OBJS) $(TARGET).out $(TARGET).map
%.o : %.c
$(CC) -c $< $(CFLAGS) -o $#
OBJS = $(SOURCES:.c=.o)
$(TARGET).out: $(OBJS)
$(CC) $(OBJS) $(CFLAGS) $(LDFLAGS) -o $#
Is this the right way of doing it?(all the tabs and indents for the make file has been given properly, though it is not seen in the code here)
Iam getting this as the error
main.c:23:10: fatal error: platform.h: No such file or directory
#include "platform.h"
^~~~~~~~~~~~
compilation terminated.
Makefile:67: recipe for target 'main.o' failed
make: *** [main.o] Error 1
Also this is my source.mk file
SOURCES = Desktop/ese-coursera-course1/assessments/m2/src
# Add your include paths to this variable
INCLUDES = Desktop/ese-coursera-course1/assessments/m2/include/common/platform.h
Can anyone help me out?

Answer 1

First, try to make sure all paths you give are relative to the Makefile.
I'm surprised your compiler actually does anything since your SOURCES variable is a directory, not a list of .c files. It should probably look like:
SOURCES = src/main.c
this will make OBJS contain src/main.o and the implicit rule will be able to fire.
Next, the INCLUDES variable should reference a directory using the -I flag, like so:
INCLUDES = -Iinclude/common
You should then use it in the CFLAGS definition as follows:
CFLAGS = -Wall -Werror -g -O0 -$(CPP) $(INCLUDES) -std=c99
Other things I noticed:
Your LDFLAGS unconditionally uses the msp432p401r.lds linker script, even in the HOST case. This should probably be added conditionally in the ifeq block like so: LDFLAGS += -T msp432p401r.lds. You should be careful not to overwrite LDFLAGS later with LDFLAGS=, so it is best if you move the definition of CFLAGS and LDFLAGS to the top of the file or always use += to modify these variables.
Following on from that: if your link step uses the linker script, you should add an explicit rule that encodes this dependency: $(TARGET).out: $(LINKER_FILE).
The build -> all -> $(TARGET).out dependency chain is a bit redundant. Why not make build directly depend on $(TARGET).out?