defcfun (name-and-options return-type &body args)

foreign-name -- A string denoting a foreign function.
arg-name -- A symbol.
return-type, arg-type -- A foreign type.
convention -- One of :cdecl (default) or :stdcall.
library -- A symbol designating a foreign library.
docstring -- A documentation string.

A symbol naming the Lisp function to be created.

The defcfun macro provides a declarative interface for defining Lisp functions that call foreign functions.

When one of lisp-name or foreign-name is omitted, the other is automatically derived using the following rules:

• Foreign names are converted to Lisp names by uppercasing and replacing underscores with hyphens.
• Lisp names are converted to foreign names by lowercasing and replacing hyphens with underscores.

If you place the symbol &rest in the end of the argument list after the fixed arguments, defcfun will treat the foreign function as a variadic function. The variadic arguments should be passed in a way similar to what foreign-funcall would expect. Unlike foreign-funcall though, defcfun will take care of doing argument promotion. Note that in this case defcfun will generate a Lisp macro instead of a function and will only work for Lisps that support foreign-funcall.

  (defcfun "strlen" :int
    "Calculate the length of a string."
    (n :string))


  CFFI> (strlen "123")
  => 3


  (defcfun ("abs" c-abs) :int (n :int))


  CFFI> (c-abs -42)
  => 42  

Function without arguments:

  (defcfun "rand" :int)


  CFFI> (rand)
  => 1804289383  

Variadic function example:

  (defcfun "sprintf" :int
    (str :pointer)
    (control :string)
    &rest)


  CFFI> (with-foreign-pointer-as-string (s 100)
          (sprintf s "%c %d %.2f %s" :char 90 :short 42 :float pi
                   :string "super-locrian"))
  => "A 42 3.14 super-locrian"