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From: "Óscar Fuentes" <ofv@wanadoo.es>
To: help-gnu-emacs@gnu.org
Subject: Re: A guide on setting up C/C++ development environment for Emacs
Date: Wed, 27 Aug 2014 20:31:24 +0200	[thread overview]
Message-ID: <877g1taio3.fsf@wanadoo.es> (raw)
In-Reply-To: 657f2c39-422b-4289-a02e-3d03dc386166@googlegroups.com

solidius4747@gmail.com writes:

> Because real parsing takes time and such a task, while possible using
> Emacs Lisp, but is too much for current Emacs implementation. CEDET
> does some nice optimizations to speed it up as fast as it can: idle
> parsing, caching and incremental parsing to reduce computational time.
> Consider someone using Clang to generate tag database:
> https://github.com/drothlis/clang-ctags#performance:
>
> "Running clang-ctags over a much larger input, such as the entire llvm
> C/C++ sources (7k files, 1.8 million lines of code) took 98 minutes
> and a peak memory usage of 140MB."
>
> It's just 1.8 million lines of code. And that's Clang.

That's a problem of clang-ctags being slow, not Clang being *so* slow,
because Clang can compile its own sources on a fraction of time of those
98 minutes (15 minutes here on a 6 year old 4core machine, for an
optimized build.)

> GNU Global only
> needs a few minutes to generate tag database for Linux kernel, which
> is more than 14 million lines of code and more than 40k files. Do you
> say Clang is worse than GNU Global?

I'll say that parsing those 1.8 MLoc of C++ code is much more demanding
than parsing 14 MLoc of C code. And the level of analysis GNU Global
does is incomparable with a real compiler and it is a long stretch to
put it on the same tool category as Clang (or even Semantic's own
parser.)

GNU Global has its uses, but C++ auto completion needs Clang, which is
accurate but slow. I can't see how CEDET could be acceptably fast and
accurate at the same time.




  reply	other threads:[~2014-08-27 18:31 UTC|newest]

Thread overview: 59+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-08-27  7:05 A guide on setting up C/C++ development environment for Emacs solidius4747
2014-08-27 12:48 ` Dmitriy Igrishin
2014-08-27 13:18   ` Tu Hoang Do
2014-08-27 14:15     ` Dmitriy Igrishin
     [not found]       ` <CAMd9FiKzwc1QKa3KtZPFpTGs86bupRptFqL_WwCSE3kPGARXfg@mail.gmail.com>
2014-08-27 14:53         ` Fwd: " Tu Hoang Do
     [not found]           ` <CAAfz9KNL25WboPXG87Azd_6yVr8zrx6hNrCsmuWs6w_XTvdspQ@mail.gmail.com>
     [not found]             ` <CAMd9FiJyjk78a-3yMatvca3qp+pr4O+GmDp03ZqFSkpAEoxhGw@mail.gmail.com>
2014-08-27 18:14               ` Tu Hoang Do
2014-08-27 18:15                 ` Jai Dayal
2014-08-27 18:37                   ` Óscar Fuentes
2014-08-27 18:42                     ` Jai Dayal
2014-08-27 18:42                       ` Jai Dayal
2014-08-27 18:52                         ` Óscar Fuentes
2014-08-27 19:05                           ` Jai Dayal
2014-08-27 19:28                             ` Óscar Fuentes
2014-08-27 19:32                               ` Jai Dayal
2014-08-27 20:06                                 ` Óscar Fuentes
2014-08-27 20:11                                   ` Jai Dayal
2014-08-27 20:57                                     ` Óscar Fuentes
2014-08-27 23:17                                       ` Jai Dayal
2014-08-27 23:47                                         ` Óscar Fuentes
     [not found]                                       ` <mailman.7678.1409181490.1147.help-gnu-emacs@gnu.org>
2014-08-28  3:30                                         ` Rusi
2014-08-28  3:33                                           ` Jai Dayal
2014-08-28  4:29                                           ` Óscar Fuentes
     [not found]                                           ` <mailman.7693.1409200204.1147.help-gnu-emacs@gnu.org>
2014-08-28  5:39                                             ` Rusi
2014-08-28 12:27                                               ` Jai Dayal
     [not found]                                               ` <mailman.7714.1409228889.1147.help-gnu-emacs@gnu.org>
2014-08-28 15:53                                                 ` solidius4747
2014-08-28 21:22                                                   ` Óscar Fuentes
2014-08-28 22:24                                                     ` Stefan Monnier
2014-08-28 23:28                                                       ` Dmitry
2014-08-29  0:02                                                       ` Óscar Fuentes
     [not found]                                                       ` <mailman.7793.1409270604.1147.help-gnu-emacs@gnu.org>
2014-08-29  3:35                                                         ` Stefan Monnier
2014-08-29  6:06                                                     ` David Engster
2014-08-29 13:09                                                       ` Óscar Fuentes
2014-08-29 13:16                                                         ` Jai Dayal
2014-08-29 13:45                                                           ` Óscar Fuentes
2014-08-29 13:52                                                         ` David Engster
2014-08-29 14:16                                                           ` Óscar Fuentes
     [not found]                                                     ` <mailman.7808.1409292429.1147.help-gnu-emacs@gnu.org>
2014-08-29 13:15                                                       ` Rusi
2014-08-28 17:08                                                 ` Rusi
2014-08-28 17:13                                                   ` Jai Dayal
2014-08-28 19:43                                                     ` Marcin Borkowski
2014-08-28 19:47                                                       ` Jai Dayal
2014-08-28 20:15                                                         ` Marcin Borkowski
     [not found]                                                   ` <mailman.7743.1409246061.1147.help-gnu-emacs@gnu.org>
2014-08-28 17:26                                                     ` Rusi
2014-08-28 23:01                                                   ` Thorsten Jolitz
2014-08-27 18:45                     ` Óscar Fuentes
2014-08-27 14:39     ` Thien-Thi Nguyen
     [not found]     ` <mailman.7608.1409150189.1147.help-gnu-emacs@gnu.org>
2014-08-27 15:01       ` solidius4747
2014-08-27 18:31         ` Óscar Fuentes [this message]
     [not found] <mailman.127014.1409321829.1146.help-gnu-emacs@gnu.org>
2014-08-29 14:33 ` Tory S. Anderson
2014-08-29 17:21   ` Jai Dayal
2014-08-29 18:11     ` Marcin Borkowski
2014-08-29 18:15       ` Jai Dayal
2014-08-29 18:27       ` Marcin Borkowski
2014-08-29 18:34         ` Jai Dayal
2014-08-29 19:17           ` Marcin Borkowski
     [not found]     ` <mailman.7863.1409335908.1147.help-gnu-emacs@gnu.org>
2014-08-30  3:43       ` Rusi
2014-08-30  7:24         ` Thien-Thi Nguyen
2014-08-30 21:27         ` Jai Dayal
     [not found]         ` <mailman.7951.1409434065.1147.help-gnu-emacs@gnu.org>
2014-08-31  1:53           ` Rusi

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