Question

Suppose we have client-server application, compiling by one makefile. Server uses libtask for parallel clients serving. Client uses ncurses for some graphic.
directory tree looks like this:

./
--bin/
--obj/
--src/
----client/*.c
----server/*.c
--makefile

So, here is makefile. Can we simplify it? I read some related questions on stackoverflow and I think it almost ideal, except of linking binaries, when we can see repeated commands. Some suggestions for style/cross-platform working will be useful. Thank you!

.PHONY: all clean

TASKLIB = -ltask
CURSESLIB = -lncurses
CFLAGS = -Wall -Werror -pedantic

bin = server client
obj_dir = obj
bin_dir = bin
ssource := src/server
csource := src/client
search_wildcard s := $(addsuffix /*.c, $(ssource))
search_wildcard c := $(addsuffix /*.c, $(csource))
sobjs = $(addprefix $(obj_dir)/, $(patsubst %.c, %.o, $(notdir $(wildcard $(search_wildcard s)))))
cobjs = $(addprefix $(obj_dir)/, $(patsubst %.c, %.o, $(notdir $(wildcard $(search_wildcard c)))))

all: $(bin)
    @echo "done!"

server: CFLAGS+=$(TASKLIB)
client: CFLAGS+=$(CURSESLIB)

clean:
    rm $(sobjs) $(cobjs) $(obj_dir)/*.d $(bin_dir)/client $(bin_dir)/server

VPATH := $(ssource) $(csource)

server: $(sobjs)
    @test -d $(bin_dir) || mkdir $(bin_dir)
    @echo "Linking $(@F)..."
    @$(CC) $< $(CFLAGS) -o $(bin_dir)/$@

client: $(cobjs)
    @test -d $(bin_dir) || mkdir $(bin_dir)
    @echo "Linking $(@F)..."
    @$(CC) $< $(CFLAGS) -o $(bin_dir)/$@

$(obj_dir)/%.o: %.c
    @test -d $(obj_dir) || mkdir $(obj_dir)
    @echo "Compiling $(@F)..."
    @$(CC) $< $(CFLAGS) -c -MD -o $@

include $(wildcard $(obj_dir)/*.d)

Answer 1

You’re probably more general than you need to be: For example, I wouldn’t make the directories configurable – that only makes sense for destinations of an install target.

Anyway, this is how I would write your makefile (untested):

CFLAGS := -Wall -Werror -pedantic
RM := rm -f
MKDIR := mkdir -p

BINARIES := bin/server bin/client
SERVER_OBJECTS := $(patsubst src/%.c, obj/%.o, $(wildcard src/server/*.c))
CLIENT_OBJECTS := $(patsubst src/%.c, obj/%.o, $(wildcard src/client/*.c))
OBJECTS := $(SERVER_OBJECTS) $(CLIENT_OBJECTS)

.PHONY : build clean realclean

build : $(BINARIES)

clean :
    $(RM) $(OBJECTS) $(OBJECTS:%.o=%.d)

realclean : clean
    $(RM) $(BINARIES)

bin/server : LDLIBS := -ltask
bin/client : LDLIBS := -lncurses

bin/server : $(SERVER_OBJECTS)
bin/client : $(CLIENT_OBJECTS)

$(BINARIES) :
    @$(MKDIR) $(dir $@)
    $(CC) $(CFLAGS) -o $@ $^ $(LDLIBS)

include $(wildcard obj/*.d)

$(OBJECTS) : obj/%.o : src/%.c
    @$(MKDIR) $(dir $@)
    $(CC) $(CFLAGS) -c -MD -o $@ $<