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libdraw: fix icossin2() integer overflow (thanks sleepydog)

--- a/sys/src/libdraw/icossin2.c

+++ b/sys/src/libdraw/icossin2.c

@@ -227,6 +227,7 @@

 {

 	int sinsign, cossign, tan, tan10, rem;

 	short *stp, *ctp;

+	uint ux, uy;

 	if(x == 0){

 		if(y >= 0)

@@ -238,19 +239,23 @@

 	sinsign = cossign = 1;

 	if(x < 0){

 		cossign = -1;

-		x = -x;

+		ux = -x;

+	} else {

+		ux = x;

 	}

 	if(y < 0){

 		sinsign = -1;

-		y = -y;

+		uy = -y;

+	} else {

+		uy = y;

 	}

-	if(y > x){

-		tan = 1000*x/y;

+	if(uy > ux){

+		tan = 1000*(uvlong)ux/uy;

 		tan10 = tan/10;

 		stp = &cosinus[tan10];

 		ctp = &sinus[tan10];

 	}else{

-		tan = 1000*y/x;

+		tan = 1000*(uvlong)uy/ux;

 		tan10 = tan/10;

 		stp = &sinus[tan10];

 		ctp = &cosinus[tan10];

-- 

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