Abstract
In this post you will find one way, namely thanks to
CEDET, of turning your Emacs into an IDE offering features for
semantic browsing and refactoring assistance similar to what you
can find in major IDE like Visual Studio or Eclipse.
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Introduction
Emacs is a tool of choice for the developer: it is very powerful,
highly configurable and has a wealth of so called modes to improve
many aspects of daily work, especially when editing code.
The point, as you might have realised in case you have already worked
with an IDE like Eclipse or Visual Studio, is that Emacs (code)
browsing abilities are quite rudimentary... at least out of the box!
In this post I will walk through one way to configure Emacs + CEDET
which works for me. This is by far not the only way to get to it but
finding this path required several days of wandering between
inconsistent resources, distribution pitfall and the like.
I will try to convey relevant parts of what I have learnt on the
way, to warn about some pitfalls and also to indicate some interesting
direction I haven't followed (be it by choice or necessity) and
encourage you to try. Should you try to push this adventure further,
your experience will be very much appreciated... and in any case your
feedback on this post is also very welcome.
The first part gives some deemed useful background to understand
what's going on. If you want to go straight to the how-to please
jump directly to the second part.
Sketch map of the jungle
This all started because I needed a development environment to do work
remotely on a big, legacy C++ code base from quite a lightweight
machine and a weak network connection.
My former habit of using Eclipse CDT and compiling locally was not
an option any longer but I couldn't stick to a bare text editor
plus remote compilation either because of the complexity of the code
base. So I googled emacs IDE code browser and started this journey
to set CEDET + ECB up...
I quickly got lost in a jungle of seemingly inconsistent options and I
reckon that some background facts are welcome at this point as to why.
Up to this date - sept. 2013 - most of the world is in-between two
major releases of Emacs. Whereas Emacs 23.x is still packaged in many
stable Linux distribution, the latest release is Emacs 24.3. In this
post we will use Emacs 24.x which brings lots of improvements,
two of those are really relevant to us:
the introduction of a package manager, which is great and (but)
changes initialisation
the partial integration of some version of CEDET into Emacs
since version 23.2
Emacs 24 initialisation
Very basically, Emacs used to read the user's Emacs config
(~/.emacs or ~/.emacs.d/init.el) which was responsible
for adapting the load-path and issuing the right (require 'stuff)
commands and configuring each library in some appropriate sequence.
Emacs 24 introduces ELPA, a new package system and official
packages repository. It can be extended by other packages
repositories such as Marmalade or MELPA
By default in Emacs 24, the initialisation order is a bit more complex
due to packages loading: the user's config is still read but should
NOT require the libraries installed through the package system:
those are automatically loaded (the former load-path adjustment and
(require 'stuff) steps) after the ~/.emacs or
~/.emacs.d/init.el has finished. This makes configuring the
loaded libraries much more error-prone, especially for libraries
designed to be configured the old way (as of today most libraries,
notably CEDET).
Here is a good analysis of the situation and possible options.
And for those interested in the details of the new initialisation
process, see following sections of the manual:
http://www.gnu.org/software/emacs/manual/html_node/emacs/Package-Installation.html
http://www.gnu.org/software/emacs/manual/html_node/emacs/Init-File.html#Init-File
I first tried to stick to the new-way, setting up hooks in
~/.emacs.d/init.el to be called after loading the various libraries,
each library having its own configuration hook, and praying for the
interaction between the package manager load order and my hooks to be
ok... in vain. So I ended up forcing the initialisation to the old
way (see Emacs 24 below).
What is CEDET ?
CEDET is a Collection of Emacs Development Environment Tools. The
major word here is collection, do not expect it to be an
integrated environment. The main components of (or coupled with)
CEDET are:
Semantic
Extract a common semantic from source code in different languages
(e)ctags / GNU global
Traditional (exhuberant) CTags or GNU global can be used as a
source of information for Semantic
SemanticDB
SemanticDB provides for caching the outcome of semantic analysis
in some database to reduce analysis overhead across several
editing sessions
Emacs Code Browser
This component uses information provided by Semantic to offer a
browsing GUI with windows for traversing files, classes,
dependencies and the like
EDE
This provides a notion of project analogous to most IDE. Even if
the features related to building projects are very
Emacs/ Linux/ Autotools-centric (and thus not necessarily very
helful depending on your project setup), the main point of EDE is
providing scoping of source code for Semantic to analyse and
include path customisation at the project level.
AutoComplete
This is not part of CEDET but Semantic can be configured as a
source of completions for auto-complete to propose to the user.
and more...
Senator, SRecode, Cogre, Speedbar, EIEIO, EAssist are other
components of CEDET I've not looked at yet.
To add some more complexity, CEDET itself is also undergoing heavy
changes and is in-between major versions. The last standalone
release is 1.1 but it has the old source layout and activation
method. The current head of development says it is version 2.0, has
new layout and activation method, plus some more features but is not
released yet.
Integration of CEDET into Emacs
Since Emacs 23.2, CEDET is built into Emacs. More exactly parts of
some version of new CEDET are built into Emacs, but of course
this built-in version is older than the current head of new CEDET...
As for the notable parts not built into Emacs, ECB is the most
prominent! But it is packaged into Marmalade in a recent version
following head of development closely which, mitigates the
inconvenience.
My first choice was using built-in CEDET with ECB installed from the
packages repository: the installation was perfectly smooth but I was
not able to configure cleanly enough the whole to get proper
operation. Although I tried hard, I could not get Semantic to take into
account the include paths I configured using my EDE project for
example.
I would strongly encourage you to try this way, as it is
supposed to require much less effort to set up and less
maintenance. Should you succeed I would greatly appreciate some
feedback of you experience!
As for me I got down to install the latest version from the source
repositories following as closely as possible Alex Ott's advices and
using his own fork of ECB to make it compliant with most recent
CEDET:
Alex Ott's tutorial
ECB status and Alex Ott ECB fork
How to set up CEDET + ECB in Emacs 24
Emacs 24
Install Emacs 24 as you wish, I will not cover the various options
here but simply summarise the local install from sources I choose.
Get the source archive from http://ftpmirror.gnu.org/emacs/
Extract it somewhere and run the usual (or see the INSTALL file)
- configure --prefix=~/local,
- make,
- make install
Create your emacs personal directory and configuration file
~/.emacs.d/site-lisp/ and ~/.emacs.d/init.el and
put this inside the latter:
Useful Emacs packages
Using the emacs commands M-x package-list-packages interactively
or M-x package-install <package name>, you can install many
packages easily. For example I installed:
cmake-mode
cmake-project
python-mode
python-pylint
outline-magic
python-magic
color-theme-solarized
(https://github.com/sellout/emacs-color-theme-solarized)
Choose your own! I just recommend against installing ECB or other
CEDET since we are going to install those from source.
You can also insert or load your usual Emacs configuration here, simply
beware of configuring ELPA, Marmalade et al. packages after (package-initialize).
CEDET
Get the source and put it under ~/.emacs.d/site-lisp/cedet-bzr. You can either download a snapshot from http://www.randomsample.de/cedet-snapshots/ or check it out of the bazaar repository with:
Run make (and optionnaly make install-info) in cedet-bzr
or see the INSTALL file for more details.
Get Alex Ott's minimal CEDET configuration file to
~/.emacs.d/config/cedet.el for example
Adapt it to your system by editing the first lines as follows
Don't forget to load it from your ~/.emacs.d/init.el:
restart your emacs to check everything is OK; the --debug-init option
is of great help for that purpose.
ECB
Get Alex Ott ECB fork into ~/.emacs.d/site-lisp/ecb-alexott:
Run make in ecb-alexott and see the README file for more
details.
Don't forget to load it from your ~/.emacs.d/init.el:
Note
You can theoretically use (require 'ecb-autoloads)
instead of (require 'ecb) in order to load ECB by need. I
encountered various misbehaviours trying this option and finally dropped it,
but I encourage you to try it and comment on your experience.
restart your emacs to check everything is OK (you probably want to
use the --debug-init option).
Create a hello.cpp with you CEDET enable Emacs and say M-x
ecb-activate to check that ECB is actually installed.
Tune your configuration
Now, it is time to tune your configuration. There is no good recipe
from here onward... But I'll try to propose some snippets below. Some
of them are adapted from Alex Ott personal configuration
More Semantic options
You can use the following lines just before (semantic-mode 1) to
add to the activated features list:
You can also load additional capabilities with those lines after
(semantic-mode 1):
Auto-completion
If you want to use auto-complete you can tell it to interface with
Semantic by configuring it as follows (where AAAAMMDD.rrrr is the date.revision
suffix of the version od auti-complete installed by you package
manager):
and activating it in your cedet hook, for example:
Support for GNU global a/o (e)ctags
Using CEDET for development
Once CEDET + ECB + EDE is up you can start using it for actual
development. How to actually use it is beyond the scope of this
already too long post. I can only invite you to have a look at:
The Gentle Introduction
Semantic user manual
http://cxwangyi.wordpress.com/2010/08/21/using-cedet-with-emacs/
http://altom.ro/blog/emacs-python-ide-recipe
Conclusion
CEDET provides an impressive set of features both to allow your emacs
environment to "understand" your code and to provide powerful
interfaces to this "understanding". It is probably one of the very few
solution to work with complex C++ code base in case you can't or don't
want to use a heavy-weight IDE like Eclipse CDT.
But its being highly configurable also means, at least for now,
some lack of integration, or at least a pretty complex configuration. I
hope this post will help you to do your first steps with CEDET and
find your way to setup and configure it to you own taste.