[issue7632] dtoa.c: oversize b in quorem
Mark Dickinson
report at bugs.python.org
Fri Jan 8 23:18:33 CET 2010
Mark Dickinson <dickinsm at gmail.com> added the comment:
Okay, I think I've found the cause of the second rounding bug above: at the end of the bigcomp function there's a correction block that looks like
...
else if (dd < 0) {
if (!dsign) /* does not happen for round-near */
retlow1:
dval(rv) -= ulp(rv);
}
else if (dd > 0) {
if (dsign) {
rethi1:
dval(rv) += ulp(rv);
}
}
else ...
The problem is that the += and -= corrections don't take into account the possibility that bc->scale is nonzero, and for the case where the scaled rv is subnormal, they'll typically have no effect.
I'll work on a fix... tomorrow.
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<http://bugs.python.org/issue7632>
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