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Date: Sun, 5 Feb 2017 01:09:11 +0100 (CET)
From: Julius Schmidt <aiju@phicode.de>
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To: 9front@9front.org
Subject: mpmod aliasing
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X-Bullshit: agile lifecycle deep-learning locator 

mpmod has a bug when n==r and x is negative.
my best attempt at a fix:

void
mpmod(mpint *x, mpint *n, mpint *r)
{
 	int sign;
 	mpint *ns;

 	sign = x->sign;
 	ns = sign < 0 && n == r ? mpcopy(n) : n;
 	if((n->flags & MPfield) == 0
 	|| ((Mfield*)n)->reduce((Mfield*)n, x, r) != 0)
 		mpdiv(x, n, nil, r);
 	if(sign < 0)
 		mpmagsub(ns, r, r);
 	if(ns != n) mpfree(ns);
}