Subject: Fixnum procedures can be made to return non-fixnums

From: Göran Weinholt <[email-masked]>
Date: Sat, 20 Jul 2013 07:56:21 +0200

Hello schemers,

the fxdiv procedure from (rnrs) fails to check that its result is
representable as a fixnum:

scheme@(guile-user)> (import (rnrs))
scheme@(guile-user)> (fxdiv (least-fixnum) -1)
$1 = 2305843009213693952

It should raise an &implementation-restriction. Here are a few other
examples of the same problem:

scheme@(guile-user)> (fxdiv-and-mod (least-fixnum) -1)
$2 = 2305843009213693952
$3 = 0
scheme@(guile-user)> (fxdiv0 (least-fixnum) -1)
$4 = 2305843009213693952
scheme@(guile-user)> (fxdiv0-and-mod0 (least-fixnum) -1)
$5 = 2305843009213693952
$6 = 0
scheme@(guile-user)> (fxarithmetic-shift-left (greatest-fixnum) 1)
$7 = 4611686018427387902
scheme@(guile-user)> (fxarithmetic-shift (greatest-fixnum) 1)
$8 = 4611686018427387902

Tested with Guile 2.0.9.40-824b-dirty on an amd64 system.

Regards,

-- 
Göran Weinholt <[email-masked]>
"Detta skall jag visa dig medelst ett stort papper som jag har fyllt
med faktiska upplysningar!" -- August Strindberg