# vim:syntax=make:ts=8:noet:sts=8:sw=8
.SECONDEXPANSION:

programs::
.PHONY: programs clean

# Provide a way to echo (or not) depending on the flags passed to make:
# Turn off echos for -s (user asked for silence) and -n (in this context,
# it's just noise)
ifeq "$(findstring s,$(MAKEFLAGS))$(findstring n,$(MAKEFLAGS))" ""
DOECHO=@echo $(1)
DOVECHO=echo $(1)
else
DOECHO=
DOVECHO=
endif

# Certain targets are "trivial": when they are the only targets, it is not
# necessary to include (and therefore generate) dependency information.
TRIVIAL_TARGET_NAMES += clean
ifeq ($(MAKECMDGOALS),)
TRIVIAL_BUILD:=no
else
ifeq ($(filter-out $(TRIVIAL_TARGET_NAMES),$(MAKECMDGOALS)),)
TRIVIAL_BUILD:=yes
else
TRIVIAL_BUILD:=no
endif
endif

TOOBJS = $(patsubst %.c,.obj/%.o,$(1))
TODEPS = $(patsubst %.c,.obj/%.d,$(1))

# $(eval ...) allows creation of new rules, so when nothing else quite fits,
# this is your escape valve -- though probably declare_program could also be
# done with secondary expansion if it was thought through
PROGRAM = $(eval $(call declare_program,$(1),$(2)))

define declare_program
ifneq ($(CFLAGS_$(1)),)
$(1): CFLAGS := $(CFLAGS_$(1))
endif
ifneq ($(LFLAGS_$(1)),)
$(1): LFLAGS := $(LFLAGS_$(1))
endif
$(1): $(call TOOBJS, $(SRCS_$(1)))
	$$(call DOECHO,Linking $$@)
	@$(CC) -o $$@ $$^ $$(LFLAGS) 
ifneq ($(TRIVIAL_BUILD),yes)
-include $(call TODEPS, $(SRCS_$(1)))
endif
clean::
	-rm -f $(1)
programs:: $(1)
endef

%/.exists:
	@if [ ! -d $* ]; then $(call DOVECHO,Creating output directory $*;) true; fi
	@mkdir -p $*
	@touch "$@"
.PRECIOUS: %/.exists

# second expansion makes a dependency file depend on the .exists of its output
# directory, so that make creates the directory just once, instead of once per
# target as I've seen (and written!) in other systems
.obj/%.d: %.c $$(dir $$@).exists
	$(call DOECHO,Depending $<)
	@mkdir -p $(dir $@)
	@$(CC) $(CFLAGS) $(DEPCFLAGS) -MM -MT "$@ $(patsubst %.d,%.o,$@)" $< -o $@.tmp \
		&& mv $@.tmp $@

.obj/%.o: %.c $$(dir $$@).exists
	$(call DOECHO,Compiling $<)
	@$(CC) $(CFLAGS) -c $< -o $@

clean::
	-rm -rf .obj

$(foreach p,$(PROGRAMS), $(call PROGRAM,$(p)))