2011 2-25

 

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

 

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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 ...>: <variable-assignment>

<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。

 

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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

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

print

tar

dist

TAGS

check test

 

4, Checking rule

-n --just-print --dry-run --recon

Just print the command, no matter whether the targets needs to be update. Often used to debug makefile

 

-t --touch

Just update the update time of targets, and do not compile the targets.

 

-q --question

If the target didn't exist, print an error message, else do nothing.

 

-W <file>  --what-if=<file> --assum-new=<file> --new-file=<file>

Just show the command path if specified file updated.

 

5, Parameters of make

-b or -m:

ignore the compatibility to other versions.

 

-B --always-make:

Rebuild all

 

-C <dir> --directory=<dir>

Specify the directory of makefile to run

 

--debug[=<options>]

Output the debug info of make. We could specify following options:

a: output all debug info.

b: output basic debug info.

v: verbose

i: output implicit rules

j: output the detail info like PID, return code, etc.

m: output the info of reading, updating, executing makefile.

 

-d

Equal to --debug=a

 

-e --environment-overrides

Specify the env's value to override the value defined in makefile

 

-f=<file> --file=<file>

Specify the makefile to run

 

-h --help

Show help info.

 

-i --ignore-errors

Ignore errors when running a makefile

 

-I <dir> --include-dir=<dir>

Specify a directory to search when running makefile

 

-j [<jobsnum>]  --jobs[=<jobsnum>]

Specify how namy sub-shell make can invoke

 

-k --keep-going

Go even error happens

 

-l <load> --load-average[=<load] --max-load[=<load>]

Specify the load when make is running

 

-o <file> --old-file=<file> --assume-old=<file>

Do not update specified file, even the prerequisite file is newer than it.

 

-p --print-data-base

 

-r --no-builtin-rules

Forbiden all the implicit rules.

 

-R --no-builtin-variables

Forbiden all the implicit rules on variable

 

-s --silent --quiet

 

-S --no-keep-going --stop

 

-t --touch

 

-v --version

 

-w --print-directory

 

--no-print-directory

forbiden -w option

 

--warn-undefined-variables

 

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IMPLICIT RULE

 

1, Pattern Rule Introduction

<target pattern>: <prerequist pattern>

command list

 

<target pattern>: <prerequist pattern>; command list

 

e.g:

%.o: %.c

$(CC) -c $(CFLAGS) $(CPPFLAGS) $< -o $@

 

2, Auto-variable

 

$@ target files

 

$% target files only when the target is a library file

 

$< the first prerequisit file

 

$? all the prerequisit files which is newer than target, seperated by whitespace

 

$^ all the prerequisit files, seperated by whitespace, and remove the repeated file name

 

$+ like $^,but don't remove the repeated file name.

 

$* The pattern part of the target string.

 

D: directory F: file

e.g:

if $(@) is bin/run.exe

$(@F) is run.exe

$(@D) is bin/