Thanks for reporting a bug. I fixed this.
Masaharu Goto
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CINT apparently promotes case constants within
a switch statement to unsigned integers.  For
example,
void stest(Int_t a) 
{
  switch(a) {
  case 1:
    printf("%d=+1\n",a);
    break;
  case -1:
    printf("%d=-1\n",a);
    break;
  default:
    printf("Unknown %d\n",a);
    break;
  }
}
root [9] stest(1)
1=+1
root [10] stest(-1)
Unknown -1
root [11] stest(0)
0=-1
As far as I know, C/C++ allow case constants 
to be any integer, not just unsigned integers.
Or, at least, CINT ought not to covert
case -1:  --->   case 0:
but intead flag this as an error.
Glenn