Under MRB_INT64, width may be bigger than INT_MAX; fix
@@ -1034,6 +1034,9 @@ retry:
if ((flags & FWIDTH) && need < width)
need = width;
+ if (need < 0) {
+ mrb_raise(mrb, E_ARGUMENT_ERROR, "width too big");
+ }
FILL(' ', need);
if (flags & FMINUS) {
if (sign)
