`makefile` not working as expected

Question

How can I have it so that when I run make that:

• prog.s is created then prog is created if prog.s and prog does not exist
• prog.s is created if prog.s is newer than prog.c (eg. after manually modifying prog.s)
• prog.s then prog is created if prog.c is newer than prog

In other words, have make create the files it needs to build prog, if the dependencies have been modified

My current makefile:

CC = gcc
CFLAGS =
TARGET = prog

all: $(TARGET).s $(TARGET).c


$(TARGET).c: $(TARGET).s
    $(CC) $(CFLAGS) $(TARGET).s -o $(TARGET)

$(TARGET).s:
    $(CC) $(CFLAGS) -S -o $(TARGET).s $(TARGET).c


clean:
    $(RM) $(TARGET)
    $(RM) $(TARGET).s

It works if I have:

• only prog.c
• manually modified prog.s

but does not work if I have manually modified prog.c
(make: Nothing to be done for 'all'.)

Answer 1

You define your target: source in the reversed order. For instance, your assembly code depends on your C code, you must write:

$(TARGET).s: $(TARGET).c

however, you have written (wrong order)

$(TARGET).c: $(TARGET).s

Here is the version with the right order for "target: sources" :

CC = gcc
CFLAGS =
TARGET = prog

all: $(TARGET)


$(TARGET): $(TARGET).s
    $(CC) $(CFLAGS) $(TARGET).s -o $(TARGET)

$(TARGET).s: $(TARGET).c
    $(CC) $(CFLAGS) -S -o $(TARGET).s $(TARGET).c


clean:
    $(RM) $(TARGET)
    $(RM) $(TARGET).s