moused(8): char signed-ness problem with gcc 3.1

I observed gcc 2.95.4 and gcc 3.1 interpret (or maybe optimize) the
following code differently (CFLAGS=-O):

int main(void)
{
  unsigned char i = 127;
  printf("%d\n", ((char)(i << 1)) / 2);
  return 0;
}

gcc 2.95.4 says it's -1, whereas gcc 3.1 says it's 127.  On FreeBSD
char should be signed, so I suspect it's a (optimization) bug of gcc
3.1 which should be fixed.  Or we'll have to do a mass audit of the
whole src tree to check and fix the similar expressions.

In any case, this behavior makes moused(8) return a stupid value of
127 when you roll the mouse wheel up under ps/2-sysmouse-intellimouse
protocol.  Attached is a patch that makes the whole expression look
more logical and works around the above behavior at the same time.

-- 
                     /
                    /__  __            Akinori.org / MUSHA.org
                   / )  )  ) )  /     FreeBSD.org / Ruby-lang.org
Akinori MUSHA aka / (_ /  ( (__(  @ iDaemons.org / and.or.jp

"Somewhere out of a memory.. of lighted streets on quiet nights.."

Index: moused.c
===================================================================
RCS file: /home/ncvs/src/usr.sbin/moused/moused.c,v
retrieving revision 1.55
diff -u -r1.55 moused.c
--- moused.c	28 Apr 2002 11:59:30 -0000	1.55
+++ moused.c	15 May 2002 17:16:40 -0000
@@ -1972,7 +1972,7 @@
 	act->dx =    (char)(pBuf[1]) + (char)(pBuf[3]);
 	act->dy = - ((char)(pBuf[2]) + (char)(pBuf[4]));
 	if (rodent.level == 1) {
-	    act->dz = ((char)(pBuf[5] << 1) + (char)(pBuf[6] << 1))/2;
+	    act->dz = ((char)(pBuf[5] << 1) + (char)(pBuf[6] << 1)) >> 1;
 	    act->button |= ((~pBuf[7] & MOUSE_SYS_EXTBUTTONS) << 3);
 	}
 	break;

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