I'm beginning with C and makefiles.

I'm trying to compile a list of C files with GNU Make.

My code should compile all the C files in the folder into .o files along with few flags and then use these .o files to compile an executable file 'main'.

and my code is this

FLAGS=-l./-O3 -Wall -c
CFILES:=$(shell ls | grep .c)

	$(CC) $(OBJS) -o main


Don't laugh please. This is not going to work as make is not going to compile each C file separately to build the final file main.

So please help.

Thanks in advance.

7 Years
Discussion Span
Last Post by nezachem

To compile individual files you have to either write an individual rule for each object, or use a generic rule as

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

(refer to automatic variables chapter in info make for the meaning of @ and <). Put this rule in place of lines 10-11.
Also be advised that your makefile does not know that main is really a target, so it would rebuild main each time, even if nothing changed. Replace all at line 7 with main.
Another recommendation is to explicitly list the source files at line 3. If you really really want make to figure that list out, use $(wildcard *.c).
Finally, you need to spell out the objfiles dependencies on .h headers (otherwise the project wouldn't rebuild on a header modification). Add a generic rule:

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

a definition of generated .d fragments:

DEPS := $(CFILES:%.c=%.d)

and include them all:

-include $(DEPS)

After that you are pretty much set. There is still a room to perfect it.

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