You can look up both functions using foreign-symbol-pointer to decide which one to call. You'd usually call the right one using foreign-funcall-pointer, but perhaps you can defcfun both and call the right one based on the lookup.

defcfun-ing non-existent functions will yield runtime warnings on some implementations (notably SBCL) so perhaps you might want to implement both the foreign-funcall-pointer and defcfun approaches and conditionalise them accordingly.

HTH,
Luís


On Mon, May 29, 2017, 02:56 Anton Vodonosov <avodonosov@yandex.ru> wrote:
Hello,
 
OpenSSL renamed function SSLeay to OpenSSL_version_num.
So, so depending on what version of library we work with we
need to call either SSLeay or OpenSSL_version_num.
 
What is the best way to do it?
 
The following is one approach:
 
(or (ignore-errors
      (cffi:foreign-funcall "OpenSSL_version_num" :long))
    (ignore-errors
      (cffi:foreign-funcall "SSLeay" :long)))
 
 
but it won't work on Corman Lisp because it doesn't
support cffi:foreign-funcall.
 
I would like to be fully portable. Is there a better way?
 
Best regards,
- Anton