Prepending (w/out newlines) to an auto-generated dependency list for Makefiles.

Question

Not sure if the title makes sense... so I'll elaborate a bit.

I'm toying with this makefile that uses gcc's auto-dependency list generator.

At the same time, I wanted to keep a nice sorted directory structure that separates source, headers, and resources.

The layout's nice and simple like so

• MAIN
  • src
  • include
  • objects
  • dependencies

Now, the makefile dependency list generator atm is this:

$(DEP_PATH)%.d : $(SRC_PATH)%.c
    @${CC} $(CFLAGS) -MM -c $(INCLUDE) $< > $(DEP_PATH)$*.d
include $@

The idea here being that we generate the dependency rule, then include it to the make build.

and the result for say, foo1.o is:

foo1.o: src/foo1.c include/foo1.h include/foo2.h include/foo3.h

This would work fine if I labled all my objects to be found in the main directory... however since they in /main/objects instead... the make says it can't find the rule for /main/objects/foo1.o

Now, I tried this:

@echo "$(OBJ_PATH)" > $(DEP_PATH)$*.d
@${CC} $(CFLAGS) -MM -c $(INCLUDE) $< >> $(DEP_PATH)$*.d

Which the > feeds the object path to the new/overwritten file, then concatenates the GCC auto-dependency rule generation to it... but it adds the newline between the two sets.

I tried cat'ing two separate files with said info as well... but they also get the newlines.

Is there a nice way to prepend the dependency file w/out adding the newline?

Also, if you've got any real nice tutorials on makefiles, cat, and echo, I'd really appreciate it.

Thanks for any and all responses.

Answer 1

The answer to the question you asked is sed:

@${CC} blah blah blah | sed 's|^|$(OBJ_PATH)|' > $(DEP_PATH)$*.d

But you're going to have a different problem with this part:

include $@

The include directive is for Make itself, it is not a shell command (like $(CC)...). And $@ is an automatic variable, defined within the rule, not available to directives outside the rule. Instead, try something like this:

include $(DEP_PATH)/*.d

and take a look at Advanced Auto-Dependency Generation.