In message <[EMAIL PROTECTED]> on Mon, 02 Dec 2002 10:51:30 +0100, Andy
Polyakov <[EMAIL PROTECTED]> said:
appro> > levitte> bn_div_words(0xFFFFC383,0x838B4B53,0x80000000)
appro> >
appro> > Hmm, a call like that gave me an aruthmetic error on Linux...
appro>
appro> According to bc 0xFFFFC383838B4B53 / 0x80000000 = 0x1FFFF8707. The
appro> result is 33 bits or in other words the operation *overflows*. According
appro> to IA-32 manual "overflow is indicated with the #DE (divide error)
appro> rather than with the CF flag" which is why it dumps the core. This
appro> behaviour does not constitute a bug as BN_div makes sure the condition
appro> is never met.
Yeah, and I discovered a small bug late last night, as well as the
fact that bn_div_words() is supposed to return FFFFFFFF on error (or
at least if the divisor is 0).
I'm slowly getting there, there's currently another problem going on,
and I think it might have to do with dropping the lowest bit of the
divisor when that one gets diveded by two (because of some quirks with
EDIV)...
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