Makefile Demo案例

# Comments can be written like this.# File should be named Makefile and then can be run as `make <target>`.
# Otherwise we use `make -f "filename" <target>`.# Warning - only use TABS to indent in Makefiles, never spaces!#-----------------------------------------------------------------------
# Basics
#-----------------------------------------------------------------------# Rules are of the format
# target: <prerequisite>
# where prerequisites are optional.# A rule - this rule will only run if file0.txt doesn't exist.
file0.txt:
    echo "foo" > file0.txt
    # Even comments in these 'recipe' sections get passed to the shell.
    # Try `make file0.txt` or simply `make` - first rule is the default.# This rule will only run if file0.txt is newer than file1.txt.
file1.txt: file0.txt
    cat file0.txt > file1.txt
    # use the same quoting rules as in the shell.
    @cat file0.txt >> file1.txt
    # @ stops the command from being echoed to stdout.
    -@echo 'hello'
    # - means that make will keep going in the case of an error.
    # Try `make file1.txt` on the commandline.# A rule can have multiple targets and multiple prerequisites
file2.txt file3.txt: file0.txt file1.txt
    touch file2.txt
    touch file3.txt# Make will complain about multiple recipes for the same rule. Empty
# recipes don't count though and can be used to add new dependencies.#-----------------------------------------------------------------------
# Phony Targets
#-----------------------------------------------------------------------# A phony target. Any target that isn't a file.
# It will never be up to date so make will always try to run it.
all: maker process# We can declare things out of order.
maker:
    touch ex0.txt ex1.txt# Can avoid phony rules breaking when a real file has the same name by
.PHONY: all maker process
# This is a special target. There are several others.# A rule with a dependency on a phony target will always run
ex0.txt ex1.txt: maker# Common phony targets are: all make clean install ...#-----------------------------------------------------------------------
# Automatic Variables & Wildcards
#-----------------------------------------------------------------------process: file*.txt    #using a wildcard to match filenames
    @echo $^    # $^ is a variable containing the list of prerequisites
    @echo $@    # prints the target name
    #(for multiple target rules, $@ is whichever caused the rule to run)
    @echo $<    # the first prerequisite listed
    @echo $?    # only the dependencies that are out of date
    @echo $+    # all dependencies including duplicates (unlike normal)
    #@echo $|    # all of the 'order only' prerequisites# Even if we split up the rule dependency definitions, $^ will find them
process: ex1.txt file0.txt
# ex1.txt will be found but file0.txt will be deduplicated.#-----------------------------------------------------------------------
# Patterns
#-----------------------------------------------------------------------# Can teach make how to convert certain files into other files.%.png: %.svg
    inkscape --export-png $^# Pattern rules will only do anything if make decides to create the
# target.# Directory paths are normally ignored when matching pattern rules. But
# make will try to use the most appropriate rule available.
small/%.png: %.svg
    inkscape --export-png --export-dpi 30 $^# make will use the last version for a pattern rule that it finds.
%.png: %.svg
    @echo this rule is chosen# However make will use the first pattern rule that can make the target
%.png: %.ps
    @echo this rule is not chosen if *.svg and *.ps are both present# make already has some pattern rules built-in. For instance, it knows
# how to turn *.c files into *.o files.# Older makefiles might use suffix rules instead of pattern rules
.png.ps:
    @echo this rule is similar to a pattern rule.# Tell make about the suffix rule
.SUFFIXES: .png#-----------------------------------------------------------------------
# Variables
#-----------------------------------------------------------------------
# aka. macros# Variables are basically all string typesname = Ted
name2="Sarah"echo:
    @echo $(name)
    @echo ${name2}
    @echo $name    # This won't work, treated as $(n)ame.
    @echo $(name3) # Unknown variables are treated as empty strings.# There are 4 places to set variables.
# In order of priority from highest to lowest:
# 1: commandline arguments
# 2: Makefile
# 3: shell environment variables - make imports these automatically.
# 4: make has some predefined variablesname4 ?= Jean
# Only set the variable if environment variable is not already defined.override name5 = David
# Stops commandline arguments from changing this variable.name4 +=grey
# Append values to variable (includes a space).# Pattern-specific variable values (GNU extension).
echo: name2 = Sara # True within the matching rule
    # and also within its remade recursive dependencies
    # (except it can break when your graph gets too complicated!)# Some variables defined automatically by make.
echo_inbuilt:
    echo $(CC)
    echo ${CXX)}
    echo $(FC)
    echo ${CFLAGS)}
    echo $(CPPFLAGS)
    echo ${CXXFLAGS}
    echo $(LDFLAGS)
    echo ${LDLIBS}#-----------------------------------------------------------------------
# Variables 2
#-----------------------------------------------------------------------# The first type of variables are evaluated each time they are used.
# This can be expensive, so a second type of variable exists which is
# only evaluated once. (This is a GNU make extension)var := hello
var2 ::=  $(var) hello
#:= and ::= are equivalent.# These variables are evaluated procedurally (in the order that they
# appear), thus breaking with the rest of the language !# This doesn't work
var3 ::= $(var4) and good luck
var4 ::= good night#-----------------------------------------------------------------------
# Functions
#-----------------------------------------------------------------------# make has lots of functions available.sourcefiles = $(wildcard *.c */*.c)
objectfiles = $(patsubst %.c,%.o,$(sourcefiles))# Format is $(func arg0,arg1,arg2...)# Some examples
ls:    * src/*
    @echo $(filter %.txt, $^)
    @echo $(notdir $^)
    @echo $(join $(dir $^),$(notdir $^))#-----------------------------------------------------------------------
# Directives
#-----------------------------------------------------------------------# Include other makefiles, useful for platform specific code
include foo.mksport = tennis
# Conditional compilation
report:
ifeq ($(sport),tennis)
    @echo 'game, set, match'
else
    @echo "They think it's all over; it is now"
endif# There are also ifneq, ifdef, ifndeffoo = trueifdef $(foo)
bar = 'hello'
endif