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GNU GLOBAL source code tagging system

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89 pointspmoriarty20 comments

For me, the most useful information was the "Comparison with Similar Tools" table (in the OpenGrok project wiki), which was linked-to from the GNU GLOBAL page: https://github.com/OpenGrok/OpenGrok/wiki/Comparison-with-Si...

As a Vim user, the comparisons to Ctags and cscope were informative.

And the list of supported languages is impressive! Awk, Dos batch, COBOL, C, C++, C#, Erlang, Fortran, Java, JavaScript, Lisp, Lua, Pascal, Perl, PHP, Python, Ruby, Matlab, OCaml, Scheme, Tcl, TeX, Verilog, Vhdl and Vim.

The fancy language support is provided by exuberant ctags, so look into that if that excites you. As for cscope, GNU global is very similar; it's a bit slower for some things and a bit faster for others. Global can only find references, not callers/callees like cscope can. And the Debian maintainer of GNU Global thinks that the GNU Global maintainer is an idiot, and a consequence of this is that on Debian and derived distros the GNU Global package is ancient. But cscope is so similar, it doesn't really matter. Oh, and the gtags-cscope frontend global gives you is pretty much compatible with cscope, so any frontend that uses cscope will just work with gtags-cscope.

Can you elaborate on the difference between finding references (in GLOBAL) and finding callers/callees (in cscope)?

The cscope caller/callee search is apparently still just text search in the code (rather than unambiguous call-graph resolution by compilation).

Both cscope and GNU global are "just text search", but cscope's C parsing is fancier. Among other things, you can ask cscope

1. Where is symbol "foo" mentioned? 2. Where is function "foo" called? 3. What other functions does function "foo" call?

GNU global can do #1, but not #2 or #3.

Well, it seems like GNU Global while can only do #1, but does it better: http://www.farseer.cn/config/2013/11/26/ctags-cscope-gtags/

Heh? That post says its show-me-where-foo-is-defined functionality is broken sometimes, but it doesn't show it (and presumably they never filed a bug upstream either). I compared the two at some point last year, and they did produce slightly different results, with cscope being slightly more correct about something, but I don't recall exactly; they were VERY similar.

But GNU Global is being maintained, while cscope was abandoned. With GNU Global, you can actually update your database without recreating your tag database again. This is very useful for editor integration when you finish editing a file and save it.

Try helm-gtags it supports callers/callees better than scope.

Why would I do that? cscope works great.

Hmmm… JavaScript wasn't supported last time I tried GNU GLOBAL, two years ago. I'll have to check it out.

I have been using Global for about 6 years now. Mostly I use it in emacs (though at times I use the CLI version).

I use it in Linux and Windows. I mostly work on C/C++ (Linux kernel, Windows drivers etc) and also have used it for few C# projects (via exuberant ctags backend).

One real advantage I get: I switch platforms between Linux and Windows (the place I work for has both). So I use emacs in both platforms and same gtags customization works out of box in both platforms. This relieves me in learning/using new editor/tagging system for each platform.

FWIW: my dot emacs https://github.com/surki/dotemacs/blob/master/init.org

For C/C++ code that you can compile I highly recommend rtags.

It uses clang (llvm) to figure out all the cross-refs so doesn't have false positives from fuzzy matching.

rtags - https://github.com/Andersbakken/rtags vim plugin - https://github.com/lyuts/vim-rtags

Doesn't seem to run on Windows, though.

I'm all for FOSS tools, and have (and still) use ctags / cscope (mainly in vim), however the best source code referencing tool I've ever used is Understand - https://scitools.com Yes, it's commercial, however it beats anything free that I've found so far.

But can it resolve method calls (in C++, or really any language) to the correct methods, rather than just listing all methods with the same name implemented for any class?

I doubt it, since this basically requires a C++ compiler and GLOBAL does not seem to have that. Yet that is what, after years now, I'm still looking for for Vim...

Incidentally I remember there was a work in progress code navigation system posted to HN semi-recently (written in Go?), but its name eludes me. Anyone want to point me to it? I'm curious how it's progressed since it was posted.

Have you taken a look at clang complete?

And the latest available version on the most recent ubuntu and debian releases is... 5.7.1 from 6 years ago!!

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=574947

https://bugs.launchpad.net/ubuntu/+source/global/+bug/127502...

Wow. That explains dima55's comment above:

https://news.ycombinator.com/item?id=8617027

I use etags in Emacs to navigate our C source code, which is so much more effective than the brute force search I often see people use. I don't have as good a handle on our C++, C#, and Java, so I'll give this a try.

I listed several methods for navigating C/C++ source code here in my guide: http://tuhdo.github.io/c-ide.html

Hope it help.

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