+(defmacro make-alien (type &optional size &environment env)
+ #!+sb-doc
+ "Allocate an alien of type TYPE and return an alien pointer to it. If SIZE
+is supplied, how it is interpreted depends on TYPE. If TYPE is an array type,
+SIZE is used as the first dimension for the allocated array. If TYPE is not an
+array, then SIZE is the number of elements to allocate. The memory is
+allocated using ``malloc'', so it can be passed to foreign functions which use
+``free''."
+ (let ((alien-type (if (alien-type-p type)
+ type
+ (parse-alien-type type env))))
+ (multiple-value-bind (size-expr element-type)
+ (if (alien-array-type-p alien-type)
+ (let ((dims (alien-array-type-dimensions alien-type)))
+ (cond
+ (size
+ (unless dims
+ (error
+ "cannot override the size of zero-dimensional arrays"))
+ (when (constantp size)
+ (setf alien-type (copy-alien-array-type alien-type))
+ (setf (alien-array-type-dimensions alien-type)
+ (cons (constant-form-value size) (cdr dims)))))
+ (dims
+ (setf size (car dims)))
+ (t
+ (setf size 1)))
+ (values `(* ,size ,@(cdr dims))
+ (alien-array-type-element-type alien-type)))
+ (values (or size 1) alien-type))
+ (let ((bits (alien-type-bits element-type))
+ (alignment (alien-type-alignment element-type)))
+ (unless bits
+ (error "The size of ~S is unknown."
+ (unparse-alien-type element-type)))
+ (unless alignment
+ (error "The alignment of ~S is unknown."
+ (unparse-alien-type element-type)))
+ ;; This is the one place where the %SAP-ALIEN note is quite
+ ;; undesirable, in most uses of MAKE-ALIEN the %SAP-ALIEN
+ ;; cannot be optimized away.
+ `(locally (declare (muffle-conditions compiler-note))
+ (%sap-alien (%make-alien (* ,(align-offset bits alignment)
+ ,size-expr))
+ ',(make-alien-pointer-type :to alien-type)))))))
+