lecture 14

a39 a38 a36 a37 CSE 30 3: Co nc epts and T o ols fo r S oft w a re Devel o p ment Hal P e rkins Winte r 2009 Lec tu re 14? Mak efile s & Compila tion Mana ge me n t CSE 3 03 W in ter 20 09, Lectur e 14 1 a39 a38 a36 a37 Where a re W e ? Onto to ols. . . ? Ba sic s of m a k e, pa rtic u la r the conce p ts ? Some fancier m a k e featur e s (rev enge of fun ky cha racte rs) Besides the slid e s a nd on line U nix do cs, th e Sta nfo rd CSLi b note s on Un ix P rogra m ming T o ols h as a nice ove rv ie w of m a k e and oth e r to ols: ? http: //c slib ra ry .sta nfo rd .e d u/107/U nixProgr amm in gT o ols .p d f CSE 3 03 W in ter 20 09, Lectur e 14 2 a39 a38 a36 a37 On to to ols Th e la ngua ge -implem entation (p re p ro ce ss o r, compiler, link er, stand a rd -lib ra ry) is h a rd ly the only useful th ing fo r deve lop ing soft w a re. Th e rest of the c ou rse : ? T o ols (re compila tion m a nagers, ve rsion control, d e b ugge rs, p rofilers) ? Sof tw a re -e n ginee ring is sues ? A taste of C+ + ? Concur renc y ? So c ietal implication s CSE 3 03 W in ter 20 09, Lectur e 14 3 a39 a38 a36 a37 mak e make is a c la ssic p rogra m fo r controllin g wha t gets (r e )com p ile d a nd ho w. Many other su c h p rograms exis t (e.g., ant , maven , ?p roj e cts ? in IDEs , . . . ) make ha s tons of fa ncy fe a tu res , b ut on ly tw o ba sic ideas: 1. Scrip ts fo r exe cuting com mand s 2. De p e n dencie s fo r a voiding un nec es sa ry w o rk T o a void ?ju st te a c h ing m a k e featur e s? (b o rin g a nd n a rro w), let ?s fo c u s m o re on the conce p ts. . . CSE 3 03 W in ter 20 09, Lectur e 14 4 a39 a38 a36 a37 Bui ld scriptin g Progr amm ers sp e n d a lot of time ?b uildi ng? (c re a ting p rogra m s from source co de) ? Progr ams they wri te ? Progr ams other p eople w rite Progr amm ers automate re p e titive ta sks. T rivia l example: gcc -Wall -g -o myprog foo.c bar.c baz.c If you: ? Ret yp e this e very tim e: ?sha m e, shame ? ? Use u p-a rr o w o r h ist o ry : ?sha m e? (re typ e af te r logou t) ? Have a n alia s o r ba sh script: ?go o d -th inkin ? ? Have a Ma k e file: y ou ?re a head of us CSE 3 03 W in ter 20 09, Lectur e 14 5 a39 a38 a36 a37 ?Real? bu ild p ro cess es On la rge r p roje cts, you can? t o r don ?t w an t to have one bi g (set of ) com mand (s) th at re d o es e verythin g eve ry time you c h ange anythi ng. 1. If gcc did n?t c ombin e ste ps b ehin d y ou r back, you c oul d ne ed to p rep ro c es s an d c ompile each file, th e n call the link e r. 2. If a nother p rogr am (e.g., sed ) c re a te d som e C files, you w ould nee d a n ?e a rlier? step. 3. If you ha ve other outpu ts fo r the same sour c e files (e.g., javadoc ), it?s unp le a sa nt to typ e th e source files multiple tim es . 4. If you w a nt to d is tr ibute sou rc e c o d e to b e b uilt b y oth e r users. 5. If you ha ve 10 5 to 10 7 lin e s of sou rc e c o d e , you don ?t w ant to rec ompil e them all eve ry time y ou cha nge som ethin g. A sim p le sc ript ha ndles 1?4 (u se a va ria ble fo r the fi le na m es fo r 3), b ut 5 is trickier. CSE 3 03 W in ter 20 09, Lectur e 14 6 a39 a38 a36 a37 Rec o mp ilation m a n a geme nt Th e ?theo ry? b ehind a voiding un nec es sa ry com p ilation is a ?dep end e n c y dag?: ? T o create a ta rget t , you ne ed source s s 1 ,s 2 ,. . . ,s n an d a com mand c (tha t d irec tly o r indir e ctly u ses th e sou rce s) ? If t is new er tha n e very sou rc e (file -mo dification time s), assum e there is no reason to re b uild it. ? Rec u rsive bui lding: If some source s i is itself a ta rget fo r some other sou rce s, see if it needs to b e re b uilt. Etc . ? Cycle s ?m a k e no sense ? CSE 3 03 W in ter 20 09, Lectur e 14 7 a39 a38 a36 a37 Theo ry a p pli ed to C An othe r whol e le ctur e on lin king is in our fu ture (w ell, a c tu ally , w e did som e of it ea rli e r) , b ut here is w ha t you need to kn o w to da y fo r C: ? Compilin g a .c cre a te s a .o an d dep ends on all in c lu de d files (recursive ly /tr ansitively). ? Creatin g a n e xec u tabl e (?linki ng?) dep ends on .o files . ? So if on e .c file cha nge s, ju st nee d to rec re a te one .o file a nd relink . ? If a h e a der-file c h an ge s, m a y nee d to rebui ld m o re. ? Of course , th is is on ly th e sim p le st situa tion. CSE 3 03 W in ter 20 09, Lectur e 14 8 a39 a38 a36 a37 An a lg o rith m What w ou ld a p rogr am (e.g., a shell scrip t) th at did this fo r you lo ok lik e? It w ou ld tak e : ? a bu nch of tripl e s: ta rget , sour c es , com man d(s) ? a ?curr e n t ta rge t to b uild? It w ou ld c ompute w h at c omm a nds ne eded to b e exe cuted, in what o rder, a nd do it. (It w oul d de tec t c ycles an d give an err o r.) Th is is e xa c tly w h at p rogra m s lik e make , ant , an d things integrated into IDEs do! CSE 3 03 W in ter 20 09, Lectur e 14 9 a39 a38 a36 a37 ma ke basi cs Th e ?trip le s? a re typ e d in to a ?mak efi le ? lik e this: target: sources command Example: foo.o: foo.c foo.h bar.h gcc -Wall -o foo.o -c foo.c Syn tax got cha s: ? Th e colon af ter the ta rge t is re q uired. ? Comm a nd lin e s must sta rt with a T AB NO T SP A CE S ? Y ou c a n actuall y ha ve multiple c omm a nds (e xec u te d in o rd e r); if one c omm a nd span s lin e s y ou must end the p rev ious lin e with \ . ? Which sh e ll-la ngua ge interp re ts the c omm a nds? (T yp ic a lly b ash, to b e sur e se t the S H ELL va riab le in your mak e file.) CSE 3 03 W in ter 20 09, Lectur e 14 1 0 a39 a38 a36 a37 Usin g ma ke A t the p rom pt: prompt% make -f nameOfMakefile aTarget De fau lts : ? If n o -f sp ec ified, use a file named Makefile . ? If n ot ta rge t sp ec ified, use the fi rst one in th e file. T oge th e r: Y ou c a n do wnload a ta rba ll, e xtr act it, typ e make (f our cha ra c ters) and eve rything should w o rk. Actua lly , there?s typically a ?configure? step to o, fo r findi ng th ings lik e ?where is th e com pi le r? tha t gene rates the Makefile (bu t w e w on ?t get in to tha t). CSE 3 03 W in ter 20 09, Lectur e 14 1 1 a39 a38 a36 a37 Basics Sum ma ry So fa r, enough fo r h om ew o rk 4 an d basic u se. ? A to ol tha t com b ines sc ri pting with d e p e n dency a nalysis to avoid un nec es sa ry recom pi lation. ? Not la ngua ge o r to ol-s p ec ific: ju st ba sed on file -mo dification time s an d sh e ll -com man ds. Bu t there?s so m u c h mo re you w a nt to do so th at y ou r Mak e files a re : ? Sh o rt a nd mo du la r ? Easy to reuse (with differe n t fla gs , pl atfo rms, e tc.) ? Useful fo r man y ta sks ? Au tom a tic a lly main tain e d with res p e ct to dep end e n c ies . Also, read ing others? mak efile s c a n b e tou gh b ec a use of a ll th e featu res : se e info make o r e n tire b o oks. CSE 3 03 W in ter 20 09, Lectur e 14 1 2 a39 a38 a36 a37 Pr e cise review A Mak efile ha s a b unch of thes e: target: source_1 ... source_n shell_command Run nin g make target do e s th is : ? F o r each sou rce , if it is a ta rge t in the Ma k e file, p ro ces s it rec u rsive ly ? Th e n : ? If some sou rce do es n ot exis t, erro r. ? If some sou rce is n e w e r tha n the ta rge t (o r ta rget d o e s not ex ist), ru n shell_command (p re sumabl y up da te s target , bu t tha t is up to y ou ). CSE 3 03 W in ter 20 09, Lectur e 14 1 3 a39 a38 a36 a37 mak e v a riable s Y ou c a n defi n e va ri ables in a M a k e file. E xa m p le : CC = gcc CFLAGS = -Wall foo.o: foo.c foo.h bar.h $(CC) $(CFLAGS) -c foo.c -o foo.o Why d o th is ? ? Easy to chan ge thin gs once an d affe ct man y com man ds. ? Ca n c ha nge va riab le s on the com man d-line (overr ides definitions in file). (F o r e xa m p le make CFLAGS=-g .) ? Easy to reuse mos t of a Ma k efile from one ?home w o rk? to the next. ? Ca n use c on ditiona ls to se t va ria bles (using in he rite d envir onm ent va ri ables). . . . CSE 3 03 W in ter 20 09, Lectur e 14 1 4 a39 a38 a36 a37 mak e co n ditionals EXE= ifdef WINDIR # assume we are on a Windows machine EXE=.exe endif myprog$(EXE): foo.o bar.o $(CC) $(CFLAGS) -o myprog$(EXE) foo.o bar.o Other fo rms of condi tionals e xist (e .g. , a re tw o strings e q ual) CSE 3 03 W in ter 20 09, Lectur e 14 1 5 a39 a38 a36 a37 mo re va ri a b les It?s also c omm on to use va ri ables to hold list of file n ame s: OBJFILES = foo.o bar.o baz.o myprog: $(OBJFILES) gcc -o myprog $(OBJFILES) clean: rm $(OBJFILES) myprog clean is a c on v ention : re move a ny genera te d files , to ?s ta rt ov er? an d ha ve ju st the sour c e. It?s ?fun ny? b ec a use the ta rge t do e sn?t e xist and th e re a re n o sour c es, bu t tha t?s ok a y: ? If ta rge t do esn?t e xist, it must b e ?r e made? so ru n the com man ds ? Th e se ?p hony? ta rgets ha ve se veral uses , a nother is a n ?all? ta rget. . . . CSE 3 03 W in ter 20 09, Lectur e 14 1 6 a39 a38 a36 a37 ?a ll? exampl e all: prog B.class someLib.a # notice no commands this time prog: foo.o bar.o main.o gcc -o prog foo.o bar.o main.o B.class: B.java javac B.java someLib.a: foo.o baz.o ar r foo.o baz.o foo.o: foo.c foo.h header1.h header2.h gcc -c -Wall foo.c ... (similar targets for bar.o, main.o, baz.o) ... CSE 3 03 W in ter 20 09, Lectur e 14 1 7 a39 a38 a36 a37 Reven g e o f fu nny c ha racters UNIX ha c k ers just c a n?t ge t e nou gh of funn y me tacha racte rs c a n th e y? In com man ds: ? $@ fo r ta rge t ? $^ fo r a ll sou rc es ? $< fo r left-m ost sou rce ? . . . Examples : myprog$(EXE): foo.o bar.o $(CC) $(CFLAGS) -o $@ $^ foo.o: foo.c foo.h bar.h $(CC) $(CFLAGS) -c $< CSE 3 03 W in ter 20 09, Lectur e 14 1 8 a39 a38 a36 a37 Mo re fanc y stuff ? Th e re a re a lot of ?built-in? ru le s. E.g., make ju st ?kno ws ? to cre a te foo.o b y c a lling $(CC) $(CFLAGS) on foo.c . (Opin ion: mo re c on fu sin g th an helpf ul. YMMV ) ? Th e re a re ?s u ffix? rules an d ?pattern? ru le s. Example: %.class: %.java javac $< # Note we need $< here ? Rem em b e r you can pu t a ny sh e ll com man d on th e com mand -line, ev en whole scripts ? Y ou c a n rep eat ta rget n ame s to ad d m o re de p endencie s (use ful with automatic de p endency generation ). Often this stuff is mo re useful fo r re a ding mak e files th an writing your o w n (until som e d a y. . . ) CSE 3 03 W in ter 20 09, Lectur e 14 1 9 a39 a38 a36 a37 Dep end ency g en era tion So fa r, w e a re still listing dep endencies m a nu ally , e.g.: foo.o: foo.c foo.h bar.h If you fo rge t, sa y, bar.h , you c a n intro d uce subtle b ugs in y ou r p rogr am (o r if y ou ?re lucky , ge t confu sin g err o rs). Th is is not m a k e?s p roblem: It ha s no un derstand ing of differe n t p rogr amm in g langu ages , com man ds, etc ., just file-m o d times . Bu t it do es see m to o erro r-p ro n e an d busy-w o rk to have to rem emb er to up d ate d e p e n denc ie s, so there a re often lan gua ge -s p ec ific to ol s tha t do it fo r you. . . CSE 3 03 W in ter 20 09, Lectur e 14 2 0 a39 a38 a36 a37 Dep end ency- g en era to r exa m ple gcc -M ? Actua lly lots of use ful va ria nts, includin g -MM an d -MG . See man gcc ? Au tom a tic a lly creates a ru le fo r you. ? Th e n include the re sultin g file in y ou r Mak efile . ? T ypically ru n v ia a phon y depend ta rget, e .g.: depend: $(PROGRAM_C_FILES) gcc -M $^ ? Th e p rogr am makedepend com bi ne s m a ny of thes e steps; a gain it is C -sp ecific but som e oth e r la ngua ge s have th e ir o wn. CSE 3 03 W in ter 20 09, Lectur e 14 2 1 a39 a38 a36 a37 Bui ld- script summ a ry Alw a ys script c ompli c a ted tasks. Alw a ys a utomate ?wha t needs rebu ildin g? via d e p e n dency a nalysis. make is a text- b ase d p rogra m with lots of b e lls and whistles fo r d oing this. It is not lan gua ge -s p ec ific. U se it. With langu age- sp e cific to ols, y ou can a utomate dep e nd e n c y gene ration . make files ha ve this w a y of sta rting sim p le an d e nd ing up u nread able. It is w o rth k e eping them cle a n. Th e re a re c on v ention s lik e make all an d make clean com mon w h e n distrib uting source co de. CSE 3 03 W in ter 20 09, Lectur e 14 2 2