Emacs C debug help function?

["Stephen J. Turnbull" <stephen@xemacs.org>]

Shenli Zhu writes:

 > Is there any help function to display form, etc?

Yes.  Type "help user" to gdb for an annotated list.  If you don't
understand how to use them from that list, or need help interpreting
results, please ask specifically.

 > And is there any instruction files on hacking C files?

For advice on writing code, as far as I know there is a little bit in
the Emacs Lisp Reference, and for the general structure of C support
for Lisp, online there's

    http://www.xemacs.org/Documentation/21.5/html/internals.html

Warning: Emacs and XEmacs redisplays are completely different, as are
text properties and extents.  The Lisp language implementation is
pretty similar, as are the buffer and string structures.  (You need to
be a little careful with text as XEmacs still uses Mule code
internally, but it has the same formal properties, eg, finding
character boundaries in O(1), etc, and many of the same higher-level
APIs for actually handling encoding as used in Emacs.)

For the style you should use in writing code, there is the GNU coding
standard, which I believe is distributed somewhere with Emacs.  If
not, you can install XEmacs and throw away everything except the
"standards.info" file. :-)  (Sorry, we don't provide an online
version.  Probably somewhere on the GNU site?)