[logilab] Emacs turned into a IDE with CEDET

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

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.

1. Get the source archive from http://ftpmirror.gnu.org/emacs/
2. 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:

;; this is intended for manually installed libraries
(add-to-list 'load-path "~/.emacs.d/site-lisp/")

;; load the package system and add some repositories
(require 'package)
(add-to-list 'package-archives
             '("marmalade" . "http://marmalade-repo.org/packages/"))
(add-to-list 'package-archives
             '("melpa" . "http://melpa.milkbox.net/packages/") t)

;; Install a hook running post-init.el *after* initialization took place
(add-hook 'after-init-hook (lambda () (load "post-init.el")))

;; Do here basic initialization, (require) non-ELPA packages, etc.

;; disable automatic loading of packages after init.el is done
(setq package-enable-at-startup nil)
;; and force it to happen now
(package-initialize)
;; NOW you can (require) your ELPA packages and configure them as normal

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:

  ~/.emacs.d/site-lisp$ bzr checkout --lightweight \
  bzr://cedet.bzr.sourceforge.net/bzrroot/cedet/code/trunk cedet-bzr
  

• 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

  (setq cedet-root-path
      (file-name-as-directory (expand-file-name
          "~/.emacs.d/site-lisp/cedet-bzr/")))
  (add-to-list 'Info-directory-list
          "~/projects/cedet-bzr/doc/info")
  

• Don't forget to load it from your ~/.emacs.d/init.el:

  ;; this is intended for configuration snippets
  (add-to-list 'load-path "~/.emacs.d/")
  ...
  (load "config/cedet.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:

  ~/.emacs.d/site-lisp$ git clone --depth 1  https://github.com/alexott/ecb/
  

• 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:

  (add-to-list 'load-path (expand-file-name
        "~/.emacs.d/site-lisp/ecb-alexott/"))
  (require 'ecb)
  ;(require 'ecb-autoloads)
  

  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

(add-to-list 'semantic-default-submodes 'global-semantic-decoration-mode)
(add-to-list 'semantic-default-submodes 'global-semantic-idle-local-symbol-highlight-mode)
(add-to-list 'semantic-default-submodes 'global-semantic-idle-scheduler-mode)
(add-to-list 'semantic-default-submodes 'global-semantic-idle-completions-mode)

(require 'semantic/ia)
(require 'semantic/bovine/gcc) ; or depending on you compiler
; (require 'semantic/bovine/clang)

;; Autocomplete
(require 'auto-complete-config)
(add-to-list 'ac-dictionary-directories (expand-file-name
             "~/.emacs.d/elpa/auto-complete-AAAAMMDD.rrrr/dict"))
(setq ac-comphist-file (expand-file-name
             "~/.emacs.d/ac-comphist.dat"))
(ac-config-default)

...
;; customisation of modes
(defun alexott/cedet-hook ()
...
    (add-to-list 'ac-sources 'ac-source-semantic)
) ; defun alexott/cedet-hook ()

;; if you want to enable support for gnu global
(when (cedet-gnu-global-version-check t)
  (semanticdb-enable-gnu-global-databases 'c-mode)
  (semanticdb-enable-gnu-global-databases 'c++-mode))

;; enable ctags for some languages:
;;  Unix Shell, Perl, Pascal, Tcl, Fortran, Asm
(when (cedet-ectag-version-check)
  (semantic-load-enable-primary-exuberent-ctags-support))