Comment 8 for bug 1305266

On 03.05.2014 21:01, Stas Boukarev wrote:
> I get a different result:
> (SB-GMP:MPZ-POW -15546163094340153687 11)
>
  [...]
>
> Which
>
> is equal to (ldb (byte 704 0) (expt -15546163094340153687 11)), so,
> there's a problem with sign extension.
>

Yes, replace with the follow macro; I haven't committed yet, because of
the strange results when requiring the test-suite:

(defmacro with-gmp-mpz-results (resultvars &body body)
   (loop for gres in resultvars
         for res = (gensym "RESULT")
         for size = (gensym "SIZE")
         collect size into sizes
         collect `(,gres (struct gmpint)) into declares
         collect `(__gmpz_init (addr ,gres)) into inits
         collect `(,size (1+ (abs (slot ,gres 'mp_size))))
           into resinits
         collect `(when (> ,size (1- sb-bignum::maximum-bignum-length))
                    (error "Size of result exceeds maxim bignum
length")) into checks
         collect `(,res (%allocate-bignum (1+ ,size)))
           into resallocs
         collect `(setf ,res (if (minusp (slot ,gres 'mp_size)) ; check
for negative result
                                 ;(gmp-z-to-bignum-neg (slot ,gres
'mp_d) ,res ,size)
                                 (negate-bignum (gmp-z-to-bignum (slot
,gres 'mp_d) ,res ,size) nil)
                                 (gmp-z-to-bignum (slot ,gres 'mp_d)
,res ,size)))
           into copylimbs
         collect `(__gmpz_clear (addr ,gres)) into clears
         collect res into results
         finally (return
                   `(with-alien ,declares
                      ,@inits
                      ,@body
                      (let ,resinits
                        (declare (type bignum-index ,@sizes))
                        ,@checks
                        (let ,resallocs
                        ;; copy GMP limbs into result bignum
                          (sb-sys:with-pinned-objects ,results
                            ,@copylimbs)
                          ,@clears
                          (values ,@results)))))))