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5.4 Defining Bindings

 (require ffi/unsafe/define)

(define-ffi-definer define-id ffi-lib-expr
  option ...)
option = #:provide provide-id
  | #:define core-define-id
  | #:default-make-fail default-make-fail-expr
Binds define-id as a definition form to extract bindings from the library produced by ffi-lib-expr. The syntax of define-id is

(define-id id type-expr
  bind-option ...)
bind-option = #:c-id c-id
  | #:wrap wrap-expr
  | #:make-fail make-fail-expr
  | #:fail fail-expr

A define-id form binds id by extracting a binding with the name c-id from the library produced by ffi-lib-expr, where c-id defaults to id. The other options support further wrapping and configuration:

If provide-id is provided to define-ffi-definer, then define-id also provides its binding using provide-id. The provide-protected form is usually a good choice for provide-id.

If core-define-id is provided to define-ffi-definer, then code-define-id is used in place of define in the expansion of define-id for each binding.

If default-make-fail-expr is provided to define-ffi-definer, it serves as the default #:make-fail value for define-id.

For example,

(define-ffi-definer define-gtk gtk-lib)

binds define-gtk to extract FFI bindings from gtk-lib, so that gtk_rc_parse could be bound as

(define-gtk gtk_rc_parse (_fun _path -> _void))

If gtk_rc_parse is not found, then define-gtk reports an error immediately. If define-gtk is instead defined with

(define-ffi-definer define-gtk gtk-lib
   #:default-make-fail make-not-available)

then if gtk_rc_parse is not found in gtk-lib, an error is reported only when gtk_rc_parse is called.

(make-not-available name)  (#:rest list? -> any/c)
  name : symbol?
Returns a procedure that takes any number of arguments and reports an error message from name. This function is intended for using with #:make-fail or #:default-make-fail in define-ffi-definer

(provide-protected provide-spec ...)
Equivalent to (provide (protect-out provide-spec ...)). The provide-protected identifier is useful with #:provide in define-ffi-definer.