Can elisp call C functions without recompilation of emacs?
Stephen Eglen
I think what I am asking is not possible, but here goes anyway...
Here at Sussex we have an environment called POP-11, which is a lisp
style interactive AI programming environment. One of its main
features is that you can call C functions from POP-11 after the shared
object files containing the C functions have been loaded into POP-11.
This can be done interactively, and does not require either POP-11 to
be recompiled or for the C functions to be compiled with any special
options. So for example, if I write a function called add(x,y) in C,
and then compile it into a shared object, I can then call this C
function from POP-11 once I have loaded in the object file storing the
add function. Of course,one of the restrictions made on the POP:C
interface is that I think the arguments to a c function must be ints,
floats, doubles and chars, rather than abstract c data types.
This is a very useful facility, especially when debugging c functions,
since you can write the test functions in POP-11, which is an
interactive language, and so only the C functions need compiling, and
not the test functions. (I'm not sure exactly how the mechanism works
in POP-11, but I think it uses some form of incremental compiler?)
My question therefore is does emacs offer this facility of calling c
functions from elisp? I notice in the elisp info files (Writing Emacs
Primitives) that of course some emacs primitives are written in c, but
am I right in thinking that once the c function has been written, the
whole of emacs needs recompiling? If this is the case, then I guess
the compile time of emacs would be a big overhead, and probably not
worth it. Also, it looks like the c functions have to be written
especially with elisp in mind (eg use of the DEFUN macros.)
I only have access to emacs 19.27 at the moment, but if it works for
other versions, I would be interested in hearing about them.
Thanks in advance, Stephen Eglen.
--
Stephen Eglen, DPhil Student, step...@cogs.susx.ac.uk
School of Cognitive and Computing Sciences, Fax: +44-(0)1273 671320
University of Sussex, Phone: +44-(0)1273-678524
Falmer, BRIGHTON, BN1 9QH, UK http://www.cogs.susx.ac.uk/users/stephene/