[Sbcl-help] alien type declarations

[rif <rif@MIT.EDU>]

Suppose I declare an alien structure (assume (use-package :sb-alien)
thoroughout):

(define-alien-type a-struct (struct a-struct (foo unsigned-int)))

and an accessor:

(defun get-a-struct-foo (a-struct)
  (declare (type (alien (* (struct a-struct (foo (unsigned 32))))) a-struct))
  (slot a-struct 'foo))

This generates fast, efficient, non-consing code.  If I remove the
declaration, I get calls to naturalize, which compiles up closures
every time I call get-a-struct-foo, and call to get-a-struct-foo ends
up consing about 250,000 bytes.

My question is, is there any better, more concise way to write the
type declaration?  Preferably something that involves just saying I've
got a pointer to an a-struct, rather than having to actually write out
the nested list structure for the type.  This is a very simple
example, and when wrapping real libraries, I often get nested
structures with many fields, leading to enormous declarations.  Any
thoughts or ideas?

Cheers,

rif