Can elisp call C functions without recompilation of emacs?
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From: Fren Zeee on 28 Jun 2010 01:34 In 1996, Stephen Eglin asked the following question which was never answered but is of interest to people in C , Lisp and users of Emacs : http://groups.google.com/group/gnu.emacs.help/browse_thread/thread/a89c2d3ddd89768d/a2368ff6f5ea1b7b?q=%22Writing+Emacs+Primitives%22 Newsgroups: comp.emacs, gnu.emacs.help From: steph...(a)cogs.susx.ac.uk (Stephen Eglen) Date: 1996/04/10 Subject: Can elisp call C functions without recompilation of emacs? Reply to author | Forward | Print | Individual message | Show original | Report this message | Find messages by this author Can elisp call functions written in C without recompilation of emacs? 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, steph...(a)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/ |