Makefile C subdirectory rule to make obj

Question

I am running a simple Makefile with no problems:

CC=gcc
CFLAGS= -std=c99 -ggdb -Wall -I.
DEPS = hellomake.h
OBJ = hellomake.o hellofunc.o 

%.o: %.c $(DEPS)
    $(CC) -c -o $@ $< $(CFLAGS)

hellomake: $(OBJ)
    gcc -o $@ $^ $(CFLAGS)

The files are in the main project's directory:

./project/Makefile
./project/hellomake.c
./project/hellomake.h

Then I tried to organized the files, and put things like:

./project/Makefile
./project/src/hellomake.c
./project/include/hellomake.h

and extra subdirectories directories:

./project/lib
./project/obj

Then the new version of the Makefile:

IDIR =include
CC=gcc
CFLAGS= -std=c99 -ggdb -Wall -I$(IDIR)

ODIR=obj
LDIR =lib

LIBS=-lm

_DEPS = hellomake.h
DEPS = $(patsubst %,$(IDIR)/%,$(_DEPS))

_OBJ = hellomake.o hellofunc.o 
OBJ = $(patsubst %,$(ODIR)/%,$(_OBJ))


$(ODIR)/%.o: %.c $(DEPS)
    $(CC) -c -o $@ $< $(CFLAGS)

hellomake: $(OBJ)
    gcc -o $@ $^ $(CFLAGS) $(LIBS)

.PHONY: clean

clean:
    rm -f $(ODIR)/*.o *~ core $(INCDIR)/*~ 

I am compiling on Linux using Emacs with the gcc compiler:

$ gcc --version
gcc (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3

Then, I run on Emacs:

<Esc> 
x
compile
make

And it gives the message:

"./project/src/" -*-
make: *** No rule to make target `obj/hellomake.o', needed by `hellomake'.  Stop.
Compilation exited abnormally with code 2 at Wed Oct  3 17:10:01

What rule should be missing to be included in the Makefile file?

All comments and suggestions are highly appreciated.

---

Thanks for your suggestion, it is added to the code. Then the compiler complains:

make -k 
make: *** No rule to make target `src/hellomake.c', needed by `obj/hellomake.o'.
make: *** No rule to make target `../include/hellomake.h', needed by `obj/hellomake.o'.
make: Target `obj/hellomake.o' not remade because of errors

Some other suggestion?

Thanks in advance!

Answer 1

To fix the error make: *** No rule to make target 'obj/hellomake.o', needed by 'hellomake'. Stop.

Change this line:

$(ODIR)/%.o: %.c $(DEPS) 

To:

$(OBJ): $(ODIR)/%.o: src/%.c $(DEPS)

This creates a rule for all objects in the $(OBJ) variable. The second parameter ('$(ODIR)/%.o') extracts the file name from the full path in order to pass just the file name to the third parameter ('src/%.c').