1

ctags, cscope

제 15 강 : ctages, cscope

2

src

include sysvmnet

sys.h inode.h user.h driver.c stream.c hd.cvm.h file.h error.h intrp.c signal.c strategy.ccdev.h bdev.h type.h read.c write.c sleep.cinit.h flt.h mount.h nfs.c super.c win.cobj.h text.h abs.h ftp.c telnet.c fill.c . . . . . . . .

. . . . .

3

#include "user.h"#include "sys.h"#include "type.h"

int sys_read (pst)struct buf *pst;{char ps[MAX];int index;

while (i ... ){ ... }

Reading Codes . . . read.c src

sysvmnet

sys.h inode.h user.h driver.c stream.c hd.cvm.h file.h error.h intrp.c signal.c strategy.ccdev.h bdev.h type.h read.c write.c sleep.cinit.h flt.h mount hnfs.c super.c win.cobj.h text.h abs.h ftp.c telnet.c fill.c . . . . . . . .

. . . . .

ex cd linux-practice/srccd lions/usr/syslscd kenvi fio.c

4

#include "user.h"#include "sys.h"#include "type.h"

int sys_read (pst) ---- who calls this?struct buf *pst; -- what is “buf”?{char ps[MAX];int index;

while ((index < MAX ) && (read (temp) != LEVEL) ) {. . . .

------------ where is read()? what does it perform?}

src

kendmr buf.h

bio

dir

Reading Codes . . . read.c

5

Looking for identifier

• grep s f -- search string• regular expression -- too much

output• Awk -- search, what next?• find -- too many directories

• Still too slow – read entire source in disk – physical limit– eg 100 men 1 year 5 minutes (1 pass)

6

Where is read() function? index file (tags file: UNIX)

from all files make index file

. . .apple p. 41orange p. 77

read file/line/patternMAX file/line/pattern

index: tags file:

word page where word is defined

Indexage 173AI 31apple 65bit 891

id file/line where id is defined

7

ctags command• man ctags

– generate tags file– used by editor– ctags –R files …

• “tag”– language objects– function name, var name, type name

• tags file– each line: (1) tag, (2) file, (3) line # or RE– eg

ex cd linux-practice cd lionsctags –Rvi tags

src

kendmr buf.h

bio

dir

8

generating tags file- awk exercise -

cd linux-practice/src/lions/usr/sys/kenlsawk ‘$0~/read\(/ {print $0}’ *.cawk '$0~/^read\(/ {print FILENAME $0}'

*.cawk '$0~/^read\(/ {print FILENAME " " NR " "

$0}' *.c

9

• [using tags index]– vi -t read when starting vi– :ta read at vi colon mode– ctrl-] to go, at vi command mode– ctrl-t to return, at vi command mode

<example> vi –t read

goto rdwr ^]goto FPIPE ^]^t

• Try long command to create my tags file for #define:

find /lions/src/usr/sys -name “*.h”

-exec awk '$0~/#define/{print FILENAME “ ” $0}' > my_tags_file {} \;

lions/src/usr/sys

kendmr buf.h ino.h

10

• [Specify which tags file]– if many tags file (projects) exist– need to tell vi which tags file to use– [on login]

• .bashrc file: export TAGPATH=/usr/src/linux/tags

– [when starting vi]• .exrc file: set tags= /usr/src/linux/tags

– [to change tags within vi]• vi• :set tags= /usr/src/linux/tags

ex try with your vi

ex does not work on this system!

ex try with your .exrc

vi –t read|

vi process looks for tags file

|which tags file?

|vi (sh var)

orsh (env var)

lions/src/usr/sys

kendmr buf.h ino.h

11

• Caveat– pathname-- use absolute pathname!

• $ ctags -R• $ ctags -R /usr/src/linux/kernel/*• $ ctags -R `pwd`/*• 3 pathnames

– Where I ran ctags (past)– Where I stored tags (many)– Where I run vi (now)

– sort -- check the version• some versions do not sort automatically

– nesting level• some versions have limits on the level of

nesting

vi searches tags file|

fetch file pathname (from tags)

|cd pathname

|relative pathname?

(./src / file.c)

12

main(){ float x, y;

x = sin(y); /*where is sin()?*/....

}

float sin(float a);{ /* ...... main body of sin() ....... }

vi editor moves to target page (using tags file)

13

• In terms of number of disk block accesses– size of (index file) << size of (entire

source)

• vi editor accesses index file (tags)

• In UNIX:– ctags command: creates tags file (index file)– vi editor: look for the identifier in the tags

file and display the new file content

14

File B

x = x + 1;

z = z + 5;

y = y - 1;

File A File C

id(tag) File loc in file

X A 133

Y B 24

Z C 177

index file (tags)

editor accesses

vi -t Y

15

Awk is ….

• Script– Awk –f X read program from awk

script file

• Example– Given *.c *.h files– Awk program– tags

file

16

Productivity• Time to find read() function?

1 second? 1 minute? productivity 10 minutes?

• Repeated hundreds, thousands of times per day no matter who/project/language/…

• Goal of timesharing system (UNIX)– Program Development Efficiency– C/UNIX mature environment (still changing ...)– java, web need more time to mature

17

Summary• Disk speed, Separate compile• Many files, directories• source code working• Need to move quickly to read()

– string search -- regular expression, grep

– traverse subtrees -- find– more faster -- ctags

18

More on Ctags

19

Ctags (Unix)

• Creates tags from – C, C++, Yacc, Lex, Pascal, Fortran,

Lisp, …

• tags : sorted index locations of object declarations

• Objects include – functions, procedures, global variables,

macros, structs, typedefs, yacc tokens, methods and classes

– Still changing (you must check ctags version …)

20

Exuberant Ctags• Less fooled by code containing #if • Included in RedHat Linux 5.2• Can find all types of C language tags, including

– macro definitions– enumerated values(the values inside enum{…})– method definitions– external function prototypes– typedef names– ….

• Compiles on UNIX, QNX, MS-DOS, NT, Windows 95, OS/2 and the Amiga

21

Linux Cross-Reference (lxr)

• General hypertext cross-referencing tool• Versatile cross-referencing tool for

relatively large code repositories• Based on stock web technology, so

the codeview client may be chosen from the full range of available web browsers

• Main Features– the ability to jump easily to the declaration

of any global identifier(even all references to global identifiers are indexed

22

http://lxr.linux.no/source

click here

23

type any symbollike sys_fork

24

25

(Cont’d)

– quick access to function declarations, data(type) definitions and preprocessor macros -> makes code browsing more convenient

– at-a-glance overview(e.g. which code areas that will be affected by changing a function or type definition)

– hypertextual sugar, such as e-mail and include file links, are provided as well

26

cscope• symbol DB

– Rebuilds the DB only if a source file has changed– or the list of source files is different

• displays the following input fields :– Find this C symbol– Find this definition– Find functions called by this function– Find functions calling this function– Find assignments to

27

preperation for cscope

• find ….. > cscope.files /* files to parse*/

• cscope –R /* parses ALL subdirectories*/• default DB is “cscope.out”

– cscope –b /*rebuild DB, not start cscope GUI*/– or cscope –b –q /* for large DB, quick search*/

• set env variable CSCOPE_DB • set env variable EDITOR (my favorite

editor)

lions/src/usr/sys

kendmr buf.h ino.h

28

29

sys_fork

30

31

32

using cscope DB• [Method 1] Simply say “cscope” (ctrl-d to exit)

– you are inside cscope GUI (try man cscope)• “arrow” move between search types • “tab” switch between search type / result

– cscope searches & launches favorite editor ($EDITOR)

• [Method 2] Vim– you are inside Vim, then invoke cscope within Vim

• Inside vim– ctrl-] (to go) ctrl-t (to return)– ctrl-\s menu at bottom (uses of symbols)– ctrl-spacebar s repeat same search – (new window for 2nd search)

33

cscope & unwanted directories

Removing unwanted files/directories HERE=/home/my/src cd / find $HERE -path "$HERE/arch/*" ! -path "$HERE/arch/386*“ -

prune -o \ -path "$HERE/include/asm/*" ! -path "$HERE/include/asm/386/*" -

prune -o \ -name "*.[chxs]“ -print >

/home/my/cscope/cscope.files

Generating cscope database. cd /home/my/cscope # directory with 'cscope.files' cscope -b -q -k # k means “don’t include user level info.--

it is kernel”

read: http://cscope.sourceforge.net/large_projects.html

src

arch dev

386 mips

34

man find-path pattern To ignore a whole directory tree, use -

prune. For example, to skip the directory

'src/junk' and all files and directories under it,

and print the names of the other files found, use following command :

find . -path ! /src/junk‘ –prune -o -print