[Ctags-devel] [Proposal] Combining of Exuberant Ctags and GNU GLOBAL.
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[Ctags-devel] [Proposal] Combining of Exuberant Ctags and GNU GLOBAL.
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From: Shigio Y. <sh...@gn...> - 2012-10-27 06:16:09
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Hello ctags hackers, I'm a developer of GNU GLOBAL source code tagging system. <http://www.gnu.org/software/global/> Exuberant Ctags is a great tool. I wish to use it in combination with GNU GLOBAL. Here is a proposal for combining them. Sorry for a long sentence. This mail is sent to 'Exuberant Ctags developer mailing list' with Cc: 'GNU GLOBAL bug mailing list'. [Notes for people of bug-global mailing list] Please note that you can not post a message to the ctags mailing list without subscription. ------------------------------------------------------------------- Combining of Exuberant Ctags and GNU GLOBAL by Shigio YAMAGUCHI 2012/Oct/27 0. Introduction GNU GLOBAL is a source code tagging system that works the same way across diverse environments (emacs, vi, less, bash, web browser, etc). The feature of it is an ability to treat not only definitions but also references. Though it can be used in combination with Exuberant Ctags, still it is not enough. This proposal is a thing about the method of better combination of the two tools. 1. Current Status Now, you can replace the built-in parser of GNU GLOBAL by Exuberant Ctags. With some setup, gtags invokes ctags with the --format=1 and --filter option, and read tag records from it. The concrete setup method is as follows. (Installation of GLOBAL-5.8.1 or later) $ ./configure --with-exuberant-ctags=/usr/local/bin/ctags $ sudo make install (Execution of GLOBAL) $ export GTAGSCONF=/usr/local/share/gtags/gtags.conf $ export GTAGSLABEL=exuberant-ctags $ gtags # invokes ctags internally $ global -x func # locates tags func 5 test.c func() { $ _ This means that GLOBAL already supports 41 programming languages supported by Exuberant Ctags. But it cannot generate reference tags, because Exuberant Ctags does not pick up them. My proposal is to bury this lack. 2. Adding a type string to the cross reference format How about adding --gtags option to Exuberant Ctags? The --gtags option adds a type string to the cross reference format of ctags. This enables GLOBAL to treat references. <a type string> <cross reference format (level 1 or 2)> ^ | one or more blanks Type strings: (explained later) "D": definition "R": other than definition Examples -------- $ ctags -x --format=1 --gtags test.c D func 5 test.c func() { $ ctags -x --format=2 --gtags test.c D func function 5 test.c func() { We should be able to consider the type string does not belong to the cross reference format. 3. How to use a type string. Please assume the following source code. [test.c] +--------------------- 1 |sub() { 2 | ... 3 | return 1; 4 |} 5 |func() { 6 | strcpy(...); 7 | if (sub()) { 8 | ... 9 | } 10 |} +--------------------- Now, Exuberant Ctags with the --format=1 option generates the following output. $ ctags -x --format=1 test.c func 5 test.c func() { sub 1 test.c sub() { Please care about that the following symbols are ignored, since they are not a definition. 'strcpy' in the 6th line 'sub' in the 7th line When the --gtags option is specified, Exuberant Ctags may pick up reference tags with a type string like follows. $ ctags -x --format=1 --gtags test.c D func 5 test.c func() { R strcpy 6 test.c strcpy(...); <== ADD D sub 1 test.c sub() { R sub 7 test.c if (sub()) { <== ADD Algorithm of the parser may be like this. foreach of all tokens { if (symbol?) if (definition?) Put a record with "D" else Put a record with "R" <== ADD } GLOBAL can use the type string for classification of tags. Rewriting GLOBAL to accept above format, GLOBAL commands will work like follows. $ gtags # make tag files $ global -xd sub sub 1 test.c sub() { # show definitions $ global -xr sub sub 7 test.c if (sub()) { # show references $ global -xs strcpy strcpy 6 test.c strcpy(...); # show other symbols $ _ [-d] shows definitions -r shows references (defined in other places) -s shows other symbols (not defined anywhere) Please note that definitions, references and other symbols are treated separately. This means that Exuberant Ctags become a perfect parser of GLOBAL. 4. For parsers which don't support reference tags. The treatment of parsers which don't generate reference tags is easy. What is necessary is just to add a "D" string unconditionally at the head of all the records when the --gtags option is specified. $ ctags -x --format=1 --gtags test.c D func 5 test.c func() { D sub 1 test.c sub() { Though such output don't have "R" records, it is no problem. 5. Is this combination useful? for GLOBAL ---------- Although GLOBAL's language support is very poor, we can conquer the weak point by the combination. for Exuberant Ctags ------------------- Although it is difficult for Exuberant Ctags to realize reference tag support independently, it becomes easy by the combination. for parser writers ------------------ Parser writers can write a common parser which is applicable to both of Exuberant Ctags and GLOBAL. This reduces the time and efforts of them. for users --------- Users obtain the third choice, that is, Exuberant Ctags (1st), GNU GLOBAL(2nd), and Exuberant Ctags through GNU GLOBAL(3rd). 6. Postscript Of course, even if this combination is realized, parsers do not necessarily increase automatically. But it will become an infrastructure for those who try to write a new parser. Originally, GNU GLOBAL was developed as a framework for adapting ctags to large projects. Exuberant Ctags and GNU GLOBAL are complement partners, I believe. What do you think? -- End of proposal ------------------------------------------------------------------- That's all. Please ask me, if there is an unclear point. Thank you for reading a long letter. Best Regards, Shigio -- Shigio YAMAGUCHI <sh...@gn...> PGP fingerprint: D1CB 0B89 B346 4AB6 5663 C4B6 3CA5 BBB3 57BE DDA3 |
