Eliminating duplication in a Makefile - makefile

Question

This is the same Makefile as in Makefile command substitution problem, but a different question.
REBAR=./rebar
REBAR_DEBUG=$(REBAR) -C rebar.debug.config
REBAR_COMPILE=$(REBAR) get-deps compile
LAST_CONFIG:=$(shell cat config.tmp)
PLT=dialyzer/sqlite3.plt
all: config_normal compile
compile:
$(REBAR_COMPILE)
test:
$(REBAR_COMPILE) eunit
clean:
-rm -rf deps ebin priv doc/* .eunit c_src/*.o
docs:
$(REBAR_COMPILE) doc
static: config_debug
$(REBAR_DEBUG) get-deps compile
ifeq ($(wildcard $(PLT)),)
dialyzer --build_plt --apps kernel stdlib erts --output_plt $(PLT)
else
dialyzer --plt $(PLT) -r ebin
endif
cross_compile: config_cross
$(REBAR_COMPILE) -C rebar.cross_compile.config
valgrind: clean
$(REBAR_DEBUG) get-deps compile
valgrind --tool=memcheck --leak-check=yes --num-callers=20 ./test.sh
ifeq ($(LAST_CONFIG),normal)
config_normal:
echo "$(LAST_CONFIG) == normal"
else
config_normal: clean
echo "$(LAST_CONFIG) != normal"
rm -f config.tmp
echo "normal" > config.tmp
endif
ifeq ($(LAST_CONFIG),debug)
config_debug: ;
else
config_debug: clean
rm -f config.tmp
echo "debug" > config.tmp
endif
ifeq ($(LAST_CONFIG),cross)
config_cross: ;
else
config_cross: clean
rm -f config.tmp
echo "cross" > config.tmp
endif
.PHONY: all compile test clean docs static valgrind config_normal config_debug config_cross
How can I eliminate (or significantly decrease) the duplication between config_normal, config_debug, and config_cross?

Answer 1

If you are using at least version 3.80 of GNU make, you can use $(eval) to create the rules from a template, like this:
define templ
ifeq ($$(LAST_CONFIG),$(config))
config_$(config):
echo "$$(LAST_CONFIG) == $(config)"
else
config_$(config):
echo "$$(LAST_CONFIG) != $(config)"
rm -f config.tmp
echo "$(config)" > config.tmp
endif
endef
$(foreach config,normal debug cross,$(eval $(templ)))