[cffi-devel] Problem with SDL_Init using CFFI with Clisp in Windows 98

[Jeremy Smith]

Hi,

I'm posting this to the CFFI discussion group, I previously posted it to
the Lisp Application Builder list.

Anyway, the L/AB people have made an SDL module that lets CFFI-supported
Lisps use SDL (it's a very portable gaming library).

I use Clisp exclusively, so I wanted to see SDL work properly with it,
just so I can develop my application using it. At first I wrote my own
SDL header module using ah2cl.lisp, but later I came across the L/AB
module, and used that instead.

What I'm getting to is, I read on comp.lang.lisp that the CFFI-based SDL
module does not work on Windows 98 under Clisp. I just tested it on my
Windows 98 laptop (P166 :-) and it says the same thing. "FFI:
FOREIGN-LIBRARY-FUNCTION: No dynamic object named 'SDL_Init' in library
:DEFAULT"

My hack that uses FFI (not CFFI) to run SDL works fine on Windows 98, so
the issue is definitely part of CFFI.

I did a little bit of detective work:

Clisp's top-level view shows the scope, at the time of the above error
as (from src/cffi-clisp.lisp):

      `(funcall
        (load-time-value
         (ffi::foreign-library-function
          ,name (ffi::foreign-library :default)
          nil (ffi:parse-c-type ',ctype)))
        , at fargs))))

The FFI documentation says nothing about a load-time-value, and
ffi::foreign-library is not mentioned either. Strange!

My best guess is that CFFI is doing something strange with CLisp's FFI
that has a better alternative. This feature of FFI that the CFFI
developers chose may be broken on Windows 98.

For a comparison, here is my SDL header code, which does work on Windows
98:

(ffi:def-call-out SDL_Init
                  (:name "SDL_Init")
                  (:library "sdl.dll")
                  (:return-type ffi:int)
                  (:arguments (flags Uint32)))

Okay, I could say "it works this way, but CFFI does it another way that
is broken", but I don't know the ins and outs of CFFI, and why the
developers chose to use the load-time-vaue macro (or whatever it is), so
I won't comment on a better way to do it. But maybe CFFI's CLisp module
could use a different feature of FFI to do its run-time DLL calls.

Anyway, CFFI is a great project, and I had no headaches setting it up,
so I'm very pleased with it. I don't even use Windows 98 (I'm on Windows
XP), but it seems best to fix things so that my application and others
will run on that platform, without people cursing Lisp.

Cheers,

Jeremy.
-- 
| Jeremy Smith BSc (Hons)
| Chief Scientist, Decompiler Technologies
| Member, British Computer Society
| England