ECL's unstable version (in CVS) now contains means both to call C functions and to export functions to the C world (callbacks). Furthermore, this project, initiated by M. Goffioul, has led to an implementation that, at least on the Intel platform, does not rely on the C compiler, but on assembler code generated run time. We hope to port this to the remaining architectures: PPC, Sparc, x86_64
If you want to test it, save the code below in a file called "example.lsp" and load it in the interpreter (if on x86/Windows,Linux,FreeBSD) or compile it and load it (if on other platforms).
The output should look as follows: the first column is the input value, the second and fourth column are the output of either a callback or a C function (in this case "sin"). Other columns are provided to compare accuracy of the result.
0 1.0 1.0 0.0 0.0 1 2.0 2.0 .841470985 0.84147096 2 3.0 3.0 .909297427 0.9092974 3 4.0 4.0 .141120008 0.14112 4 5.0 5.0 -0.7568025 -0.7568025 5 6.0 6.0 -.95892427 -0.9589243 6 7.0 7.0 -0.2794155 -0.2794155 7 8.0 8.0 .656986599 0.6569866 8 9.0 9.0 .989358247 0.98935825 9 10.0 10.0 .412118485 0.4121185
;; Notice that the following example will work on all platforms if compiled
;; as in
;; (COMPILE-FILE "example.lisp")
;; (LOAD-FILE "example")
;; However, on the x86 platform (i.e. Intel running Linux, FreeBSD, Windows,
;; etc on 32 bit modes), this example also works when loaded from the
;; interpreter. In this case, assembly code is built at run-time and there
;; is no need to have a C compiler around. Ports to other architectures are
;; being developed and any kind of help is welcome.
;; This is a "callback", i.e. a function that can be called from the C world.
;; We can retreive a UFFI pointer to this function using #'FFI:CALLBACK, as
;; shown below.
(ffi:defcallback increment :double ((x :double))
;; This is a foreign function, i.e. a C function that can be called from the
;; lisp world. Here we do not need to handle pointers: a lisp function called
;; C-SIN is created that does the job of translating arguments for us. The
;; syntax here is pure UFFI.
(ffi:def-function ("sin" C-sin) ((x :double)) :returning :double :module :default)
(format t "Value 1+ (cback) lisp sin(cfun) lisp ~%")
(format t "=====================================================~%")
(dotimes (i 10)
(format t "~10D ~10f ~10f ~10f ~10f~%"
(si::call-cfun (ffi:callback 'increment) :double '(:double) (list i))