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7 Foreign Function Calling

— Macro: %foreign-funcall name {arg-type arg}* &optional result-type => object
— Macro: %foreign-funcall-pointer ptr {arg-type arg}* &optional result-type => object

Invoke a foreign function called name in the foreign source code.

Each arg-type is a foreign type specifier, followed by arg, Lisp data to be converted to foreign data of type arg-type. result-type is the foreign type of the function's return value, and is assumed to be :void if not supplied.

%foreign-funcall-pointer takes a pointer ptr to the function, as returned by foreign-symbol-pointer, rather than a string name.


     ;; Calling a standard C library function:
     (%foreign-funcall "sqrtf" :float 16.0 :float) => 4.0
     ;; Dynamic allocation of a buffer and passing to a function:
     (with-foreign-ptr (buf 255 buf-size)
       (%foreign-funcall "gethostname" :pointer buf :size buf-size :int)
       ;; Convert buf to a Lisp string using MAKE-STRING and %MEM-REF or
       ;; a portable CFFI function such as CFFI:FOREIGN-STRING-TO-LISP.