[Openmcl-devel] Executing CCL from within C/C++

[Pascal J. Bourguignon]

Josh Hamell <jhamell at sift.net> writes:

> Hi,
>
> We have had great experiences using CCL on a number of different
> projects in different capacities, and are now looking at a very niche
> use case.
>
> Within Linux, is it possible to compile a C/C++ program against
> lisp-kernel headers, link against the binary (lx86cl64), and execute
> arbitrary Lisp code as input char* s-expressions?  Naively, I can peruse
> the exposed functions using objdump, and would like to believe in a
> simple way to start the interpreter, load an existing heap image, and
> run, all through simple C.  This is sort of a "reverse CFFI" - our issue
> is that the C code needs to be the application entry point, without
> resorting to separate processes.
>
> We have looked at another Common Lisp implementation which supports this
> kind of interaction, but have come away with some serious issues which
> we do not have the resources to address on this project.

Have a look at:  http://www.xach.com/lisp/lispvan-2008-02-28.pdf


While it would be trivial to rename main into ccl_main, and to link it
as a library instead of an executable, it wouldn't be too useful given
that this "libccl" would still:
1- expect ccl_main to be called from the main thread,
2- preempt unix signals, 
3- manage the threads (and possibly the memory, I don't know),
in such a way that the rest of your C program would have a hard time
doing almost anything.


The problem is not the "entry point", but rather those questions of
threads and signals.  Some of the related resources are unique in a unix
process, so all the code must manage their shared access.  (Just to take
a single example, alarm(2) uses SIGALRM, and therefore only one single
alarm can be set up at a given time; so two "libraries" used in a
program cannot use it at the same time).


Finally,  you may consider ecl (libecl.so) which is already designed to
be used as a library in a C program.  

-- 
__Pascal Bourguignon__                 http://www.informatimago.com/
“The factory of the future will have only two employees, a man and a
dog. The man will be there to feed the dog. The dog will be there to
keep the man from touching the equipment.” -- Carl Bass CEO Autodesk