Writing Makefiles

Pattern Rules

A pattern rule can be used to define a generic recipe for turning a file of type X into a file a type Y for example, compiling program.c into program.o. A pattern rule can be defined as follows

%.o: %.c
	$(CC) -c $(CFLAGS) $< -o $@

• %.o/%.c Will match files of the form *.o and *.c respectively
• $< can be used to reference all the dependencies of the target, in this case the *.c file.
• $@ can be used to reference the target itself, in this case the $@ file

Example

.POSIX:

CC = gcc
CFLAGS = -Wall $(shell pkg-config --cflags xcb-image)
LDLIBS = $(shell pkg-config --libs xcb-image)

default: main

debug: CFLAGS += -g
debug: main

main: main.o
	$(CC) $< -o $@ $(LDLIBS)

%.o: %.c
	$(CC) -c $(CFLAGS) $< -o $@

Links

• Automatic Variables
• Pattern Rules
• Writing Portable Makefiles