You can use the C interface to call ___alloc_scmobj with the first argument equal to the processor state, or call ##still-copy to make a still copy of an existing u8vector:


;; this code is specific to the C backend

(define (make-u8vector-still len)
  (let ((result
         ((c-lambda
              (unsigned-int)
              scheme-object
            "___SCMOBJ result = ___EXT(___alloc_scmobj) (___ps, ___sU8VECTOR, ___arg1);
             if (!___FIXNUMP(result))
               ___still_obj_refcount_dec (result);
             ___return(result);
            ")
          len)))
    (if (##fixnum? result)
        (begin
          (##raise-heap-overflow-exception)
          (make-u8vector-still len))
        result)))

(define still?
  (c-lambda
      (scheme-object)
      bool
    "___return(___HD_TYP(___HEADER(___arg1)) == ___STILL);"))


(pp (still? (make-u8vector 1000))) ;; #f (small objects are movable)

(pp (still? (make-u8vector 3000))) ;; #t (large objects are still)

(pp (still? (##still-copy (make-u8vector 10)))) ;; #t (make a still copy)

(pp (still? (make-u8vector-still 10))) ;; #t (allocated as still even if small)


Marc



> On Nov 15, 2019, at 3:39 AM, Dimitris Vyzovitis <vyzo@hackzen.org> wrote:
>
> What's the magic incantation to allocate a still u8vector?
> I can't seem to find any primitive procedure (in scheme or in C) for this.
>
> -- vyzo
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