libmemdraw: fix int size bug

R=rsc, quanstro CC=plan9port.codebot http://codereview.appspot.com/6657043
2012-10-21 12:08:49 -04:00 · 2012-10-21 12:08:49 -04:00 · 33cdf63251
commit 33cdf63251
parent c5bfba483f
1 changed files with 2 additions and 1 deletions
--- a/src/libmemdraw/alloc.c
+++ b/src/libmemdraw/alloc.c
@ -141,7 +141,8 @@ byteaddr(Memimage *i, Point p)
 {
 	uchar *a;

-	a = i->data->bdata+i->zero+sizeof(u32int)*p.y*i->width;
+	/* careful to sign-extend negative p.y for 64-bits */
+	a = i->data->bdata+i->zero+(int)(sizeof(u32int)*p.y*i->width);

 	if(i->depth < 8){
 		/*