From: cinap_lenrek@felloff.net
To: 9front@9front.org
Subject: Re: [9front] libmemdraw memarc bug
Date: Thu, 7 Mar 2019 20:03:21 +0100 [thread overview]
Message-ID: <7C4A4B9D678C217C56E3A03E1D80B26D@felloff.net> (raw)
In-Reply-To: CAH_zEu77jC=ZrZfyyU4yJ50aw6u3k=-qoC4G5gAxyg0kLFK7Cg@mail.gmail.com
this is a sneaky one because it looks like phi should never
be negative given that we flip the sign when phi < 0 in the
first if() below. however, here is a singularity when phi equals
-0x80000000 (which is the same as 0x80000000 in twos complement).
if(phi < 0){
tmp = alpha;
alpha = beta;
beta = tmp;
phi = -phi;
}
+ if(phi < 0)
+ phi = 0;
if(phi >= 360){
memellipse(dst, c, a, b, t, src, sp, op);
return;
}
the same issue is at the top:
if(a < 0)
a = -a;
if(b < 0)
b = -b;
also, stupid stuff like:
while(alpha < 0)
alpha += 360;
while(beta < 0)
beta += 360;
so i'd say back to the drawing board...
--
cinap
next reply other threads:[~2019-03-07 19:03 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-07 19:03 cinap_lenrek [this message]
2019-03-09 22:40 ` Nick Owens
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