Instead of the flat structure my code currently has, I want to organize it into modules contained in sub-folders (and perhaps sub-sub folders if the modules get big enough).
Each module will have one or more translation units which will each produce a .o file. The final target would be to mash up all these object files into a static library (for now).
I am using plain 'make' and it is already complicated enough.
Is there a system in which the specified model comes naturally or with much less effort compared to writing makefiles by hand ?
(If you are going to recommend cmake, I need some hints as I have already tried and could not come up with a good solution.)
Some paraphrased bits from my current project's makefile that may help you out with good old fashioned GNU make:
SOURCEDIR := dir1 dir2/subdir1 dir3 dir4 dir5/subdir1 dir6/subdir1
SOURCES := $(foreach srcdir,$(SOURCEDIR),$(wildcard $(srcdir)/*.c))
OBJECTS := $(patsubst %.c,build/%.o,$(SOURCES))
OBJDIRS := $(addprefix build/,$(SOURCEDIR))
MAKEDEPS := $(patsubst %.c,build/%.d,$(SOURCES))
all: example
$(OBJDIRS):
-mkdir -p $@
build: $(OBJDIRS)
build/%.o : %.c | build
cc -MMD -c -o $@ $<
example: $(OBJECTS)
cc -o $@ $(OBJECTS)
-include $(MAKEDEPS)
In essence, it builds all of the source files found in the designated directories into object files located in subdirectories of the build directory in a hierarchy that parallels their source directory layout (important if multiple source files have the same name) and then links the results into an executable example.
As a bonus, dynamic dependency generation and inclusion via the MAKEDEPS variable and clang's -MMD flag.