Makefile for a simple C project

I recently wrote down a short introduction to GNU make (in French). If you already understand the rules of the following Makefile, it’s actually not worth reading it ;-) But here is the practical use case:

SRC = *.c
OBJ = $(SRC:.c=.o)
BIN = mybin
CFLAGS = -Wall -O2

all: $(BIN)

$(BIN): $(OBJ)
    gcc $^ $(CFLAGS) -o $@

%.o: %.c
    gcc -c $^ $(CFLAGS) -o $@

This simple Makefile will look for all C files in its directory, compile them to intermediate object files, then gather all these object files into one binary called mybin. Assuming you put the Makefile and C files together in the same folder, all you have to do is run:

$ make

This will call the default all rule, which depends on the binary, triggering the $(BIN) rule, which depends on all object files. Since there is a generic rule to compile %.o files from %.c files, Make will automatically infer what it should do, compile the source files into objects, then bind them all into the binary. Mission accomplished.

I hope this template can be as handy for you as it is for me. I always forget the special variables ($^ and $@) required to write down the generic rule, so I keep the template here and come back to copy-paste it once in a while ;-)


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