Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!ucsd!ucbvax!bloom-beacon!RPI.EDU!mckenney
From: mckenney@RPI.EDU (Bruce McKenney)
Newsgroups: comp.lang.scheme.c
Subject: Apparent bug with "*" for range 0xffc0-0xffff (R6.1.1)
Message-ID: <8910121551.AA01295@bmc.its.rpi.edu>
Date: 12 Oct 89 15:51:37 GMT
Sender: daemon@bloom-beacon.MIT.EDU
Distribution: inet
Organization: The Internet
Lines: 35


   We have encountered an apparent bug in C-Scheme when attempting to
multiply two values which are both in the range [65472..65535], which,
for all you bit-twiddlers out there, is [0x0ffc0-0xffff]. A sample:

   1 ]=> (* 65535 65535)
   
   #[SEQUENCE -#x1FFFF]
 
The value after "SEQUENCE" is evidently a function of the input values,
though it's not immediately obvious what that function might be.
   This same behaviour has been observed in the Sun-3, Sun-4, and MTS
(IBM 370) versions. A quick check with the debugger indicates that
neither multiply_signed_bignum() nor multiply_unsigned_bignum() is 
being called. I'm currently checking calls to Prim_Multiply, but 
that's a bit more of a drawn-out process.
    We are running:
Release 6.1.1
Microcode 10.2
Runtime 13.91
SF 3.13

    Has anyone else observed this? Any suggestions where to look?

    Bruce McKenney
    mckenney@itsgw.rpi.edu
    Bruce_McKenney@mts.rpi.edu
    userarkc@rpitsmts.bitnet
 
PS: Any responses are appreciated, but "fixed in Release [N+1]" would be
    less useful than "modify line NNN of file XXX.c to say...", or
    even "it sounds like Prim_Multiply is maybe goofing". We have
    a classful of students who are apparently very attached to this
    range of numbers :-), resulting in an (understandably) irritated 
    professor, i.e. a fix is needed "yesterday".