There exist multiple Emacs FFI implementations [1], [2].
None of them are included in Emacs though and that's the main issue. For something like FFI to be maximally useful, you do want it to be part of Emacs and not an additional -compiled- add-on.
The problem is not technical, but political. For years, RMS has opposed an Emacs FFI due to his belief that it could be used to subvert Emacs goals by making it possible to do proprietary extensions.
The problem is not technical, but political. For years, RMS has opposed an Emacs FFI due to his belief that it could be used to subvert Emacs goals by making it possible to do proprietary extensions.
[1] https://github.com/tromey/emacs-ffi
[2] https://github.com/skeeto/elisp-ffi