guile/HACKING

Here are some guidelines for members of the Guile developers team.

CVS conventions ======================================================

- We use CVS to manage the Guile sources.  The repository lives on
egcs.cygnus.com, in /egcs/carton/cvsfiles; you will need an account on
that machine to access the repository.  Also, for security reasons,
egcs presently only supports CVS connections via the SSH protocol, so
you must first install the SSH client.  Then, you should set your
CVS_RSH environment variable to ssh, and use the following as your CVS
root:

	:ext:USER@egcs.cygnus.com:/egcs/carton/cvsfiles

Either set your CVSROOT environment variable to that, or give it as
the value of the global -d option to CVS when you check out a working
directory.

For more information on SSH, see http://www.cs.hut.fi/ssh.

The Guile sources live in several modules:

  - guile-core --- the interpreter, QuickThreads, and ice-9
  - guile-doc --- documentation in progress.  When complete, this will
	be incorporated into guile-core.
  - guile-tcltk --- the Guile/Tk interface
  - guile-tk --- the new Guile/Tk interface, based on STk's modified Tk
  - guile-rgx-ctax --- the Guile/Rx interface, and the ctax implementation
  - guile-scsh --- the port of SCSH to guile, talk to Gary Houston
  - guile-comp --- the Hobbit compiler (talk to mdj)
  - guile-emacs --- Guile/Emacs interface (talk to mdj)
  - guile-oops --- The Guile Object-Oriented Programming System (talk to mdj)
  - guile-www --- A Guile module for making HTTP requests.

- We check Makefile.in and configure files into CVS, as well as the
files they are built from (Makefile.am, configure.in); we do not check
in Makefiles or header files generated by configuration scripts.  The
general rule is that you should be able to check out a working
directory of Guile from CVS, and then type "configure" and "make",
without running any other tools.

- Make sure your changes compile and work, at least on your own
machine, before checking them into the main branch of the Guile
repository.  If you really need to check in untested changes, make a
branch.

- Include each log entry in both the ChangeLog and in the CVS logs.
If you're using Emacs, the pcl-cvs interface to CVS has features to
make this easier; it checks the ChangeLog, and generates good default
CVS log entries from that.


Coding standards =====================================================

- As for any part of Project GNU, changes to Guile should follow the
GNU coding standards.  The standards are available via anonymous FTP
from prep.ai.mit.edu, as /pub/gnu/standards/standards.texi and
make-stds.texi.

- The Guile tree should compile without warnings under the following
GCC switches, which are the default in the current configure script:
    -O2 -Wall -Wpointer-arith -Wmissing-prototypes
The only exceptions are the warnings about variables being clobbered
by longjmp/vfork in eval.c.  (Tho' if you can figure out how to get
rid of those, too, I'd be happy.)

Note that the warnings generated vary from one version of GCC to the
next, and from one architecture to the next (apparently).  To provide
a concrete common standard, Guile should compile without warnings from
GCC 2.7.2.3 in a Red Hat 5.0 i386 Linux machine.  Furthermore, each
developer should pursue any additional warnings noted by on their
compiler.  This means that people using more stringent compilers will
have more work to do, and assures that everyone won't switch to the
most lenient compiler they can find.  :)

- When you make a user-visible change (i.e. one that should be
documented, and appear in NEWS, put an asterisk in column zero of the
start of the ChangeLog entry, like so:

Sat Aug  3 01:27:14 1996  Gary Houston  <ghouston@actrix.gen.nz>

*	* fports.c (scm_open_file): don't return #f, throw error.

When you've written a NEWS entry and updated the documentation, go
ahead and remove the asterisk.  I will use the asterisks to find and
document changes that haven't been dealt with before a release.

- There's no need to keep a change log for documentation files.  This
is because documentation is not susceptible to bugs that are hard to
fix.  Documentation does not consist of parts that must interact in a
precisely engineered fashion; to correct an error, you need not know
the history of the erroneous passage.  (This is copied from the GNU
coding standards.)

- Make sure you have papers from people before integrating their
changes or contributions.  This is very frustrating, but very
important to do right.  From maintain.texi, "Information for
Maintainers of GNU Software":

    When incorporating changes from other people, make sure to follow the
    correct procedures.  Doing this ensures that the FSF has the legal
    right to distribute and defend GNU software.

    For the sake of registering the copyright on later versions ofthe
    software you need to keep track of each person who makes significant
    changes.  A change of ten lines or so, or a few such changes, in a
    large program is not significant.

    *Before* incorporating significant changes, make sure that the person
    has signed copyright papers, and that the Free Software Foundation has
    received them.

If you receive contributions you want to use from someone, let me know
and I'll take care of the administrivia.  Put the contributions aside
until we have the necessary papers.

- When you make substantial changes to a file, add the current year to
the list of years in the copyright notice at the top of the file.


Helpful hints ========================================================

- [From Mikael Djurfeldt] When working on the Guile internals, it is
quite often practical to implement a scheme-level procedure which
helps you examine the feature you're working on.

Examples of such procedures are: pt-size, debug-hand and
current-pstate.

I've now put #ifdef GUILE_DEBUG around all such procedures, so that
they are not compiled into the "normal" Guile library.  Please do the
same when you add new procedures/C functions for debugging purpose.

You can define the GUILE_DEBUG flag by passing --enable-guile-debug to
the configure script.

- You'll see uses of the macro SCM_P scattered throughout the code;
those are vestiges of a time when Guile was meant to compile on
pre-ANSI compilers.  Guile now requires ANSI C, so when you write new
functions, feel free to use ANSI declarations, and please provide
prototypes for everything.  You don't need to use SCM_P in new code.


Jim Blandy