2011 2-25

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6, 自动生成依赖性

编译器的 -M 选项，gnu compiler则要 -MM

%d: %.c

@set -e; rm -f $@ /

$(CC) -MM $(CPPFLAGS) $< > $@.$$$$;/

sed 's, /($*/)/.o[ :]*,/1.o $@ : ,g' <$@.$$$ > $@; /

rm -f $@.$$$$

# $$$$ 自动生成的四位随机数

********************************************************************************

WRITE COMMAND

1, display the command

@echo compiling module xxx

(just print the content, not the command and the content)

make -n (or --just-print)

(This is useful to debug our makefile)

2, command error

We could add '-' before a command to ask make ignore the error returned from the command.

Or, add option "-i" or "--ignore-errors"

If a rule is the target of ".IGNORE", make will ignore all the errors from the command subtree.

If we use "-k" or "--keep-going" option, make won't break if it meet error.

3, execute make imbededly

subsystem:

cd subdir && $(MAKE)

It's equal to:

subsystem:

$(MAKE) -C subdir

4, variable export

export variable

# This is means the other makefile which is invoked by this makefile can use this variable.

export

# Export all variables of the makefile

There are two variables is constantly passed to sub makefile: SHELL & MAKEFLAGES

and of course, there is some OPTIONs could not passed to sub makefile: -C -W -f -h -o

"-w" is "--print-directory" is very useful when imbededly call makefile

If we use -C to start make sub makefile, -w is be defined defaultly.

But if we defined -s "--silent", -w is always undefined.

5, define command list

e.g:

define run-yacc

yacc $(firstword $^)

mv y.tab.c $@

endef

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USING VARIABLE

1, Basement of variable

Using variable $(var) or ${var} ($$ stand for '$')

2, Variable defined variable

The difference between '=' and ':=' (hint: recursive call)

nullstring :=

space := nullstring #mark the end of the defination

3, variable substitute

foo := a.o b.o c.o

bar := $(foo:.o=.c) is equal to

静态模式-- bar := $(foo:%.o=%.c)

4, +=

+= inherited from the pre-define of a variable.

e.g:

var := a

var += b is equal to

var := $(var) b

var = a

var += b is equal to

var = $(var) b

5, override ??

override the variable which is defined before.

Strongly substitute the variable setting from command line.

6, define

7, env

recommend: define CFLAGS, CPPFLAGS，to compile anything in the same way.

8, target based variable

<target ...>: <variable-assignment> or

<target ...>: override <variable-assignment>

e.g:

prog: CFLAGS = -g

Prog: prog.o foo.o bar.o

When compile prog module, -g flag will be used,

even when compile the sub module of prog

9, pattern variable

<pattern ...>: override <variable-assignment>

e.g:

%.o:CFLAGS = -O

********************************************************************************

CONDITION AND JUDGEING

1, Key words: ifeq else endif ifneq

Those keywords must be the head of a line.

2, make 在读取makefile时计算条件表达式，因此在条件表达式中不能出现自动化变量

因为自动化变量在运行时赋值。

********************************************************************************

USING FUNCTION

1,Grammar

$(<funciton> <arguments>) or

${<funciton> <arguments>}

2, string processing functions:

subst arg1,arg2,arg3

find substring arg1 from arg3 and substitute arg2

e.g:

$(subst ee,EE,feet on the street)

fEEt on the strEEt

patsubst <pattern>, <replacement>, <text>

pattern based string substitution

e.g:

$(patsubst %.c,%.o,x.c.c bar.c)

x.c.o bar.o

the same as

src = x.c.c bar.c

$(src:.c=.o)

override CFLAGS += $(patsubst %, -I%, $(subst :, ,$(VPATH)))

strip <string>

remove whitespace in the string from head and end.

$(strip a b c )

a b c

findstring <find>,<in>

$(findstring a, a b c ) is equal to a

$(findstring a, b c) is equal to " "

filter <pattern...>, <text>

source := x.c b.c z.s g.h

$(filter %c %s, $(source)) is equal to x.c b.c z.s

filter-out <pattern...>, <text>

filter-out is not filter

sort <list>

$(sort foo bar lose) -> bar foo lose

word <n>, <text>

get the nth word from the text

$(word 2, foo bar baz) -> bar

wordlist <s>, <e>, <text>

get a word list from the sth to eth of the text

$(wordlist 2,3,hello world is yours) -> world is

words <text>

Get the word number of text

$(words hello world!) ->2

firstword <text>

Get the first word form the text.

$(firstword hello world!) --> hello

File name operation

1, dir <names ...>

$(dir src/foo.c hacks) returns src/ ./

2, notdir <names ...>

$(notdir src/foo.c hacks) returns foo.c hacks

3, suffix <names ...>

$(suffix src/foo.c hacks) returns .c

4, basename <names ...>

$(basename src/foo.c hacks) returns src/foo hacks

5, addsuffix <suffix>, <names ...>

$(addsuffix .c, foo bar) returns foo.c bar.c

6, addprefix <prefix>, <names ...>

$(addprefix src/, foo bar) returns src/foo src/bar

7, join <list1>, <list2>

$(join aaa bbb, 111 222 333) returns

aaa111 bbb222 333

8, foreach <var>, <list>, <text>

names := a b c d

files := $(foreach n, $(names), $(n).o) returns

a.o b.o c.o d.o

9, if <condition>, <then-part> (optional), <else-part>

10, call <expression>, <parm1>, <parm2>, ...

reverse = $(2) $(1)

foo = $(call reverse,a,b)

then, foo is b,a

11, origin <variable>

Tell me where the variable borns from.

This function may return:

undefined default file "command line" override automatic environment

ifdef bletch

ifeq "$(origin bletch)" "environment

bletch = barf, gag, etc.

endif

12, shell

contents := $(shell cat foo)

files := $(shell echo *.c)

--------------------------------------------------------------------------------

CONTROL MAKE

1, error <text ...>

report an error message and break the make process.

2, warning <text ...>

report an warning message but keep going on

********************************************************************************

RUNNING MAKE

1, Return code

0: return success

1: error happend

2: Using option '-q' and some target don't need to update.

2, specified makefile "-f"

make -f (or --file --makefile) makefilename

3, specified target

MAKECMDGOALS variable is used to save the make's terminal target.

content = foo bar

sources = $(addsuffix .c,$(content))

ifneq ( $(MAKECMDGOALS), clean)

include $(sources:.c=.d)

endif

the .PHONY target list:

all

clean

install

tar

dist