localjump_error(mrb_state *mrb, localjump_error_kind kind)
{
  char kind_str[3][7] = { "return", "break", "yield" };
  char kind_str_len[] = { 6, 5, 5 };
  static const char lead[] = "unexpected ";
  mrb_value msg;
  mrb_value exc;

  msg = mrb_str_new_capa(mrb, sizeof(lead) + 7);
  mrb_str_cat(mrb, msg, lead, sizeof(lead) - 1);
  mrb_str_cat(mrb, msg, kind_str[kind], kind_str_len[kind]);
  exc = mrb_exc_new_str(mrb, E_LOCALJUMP_ERROR, msg);
  mrb_exc_set(mrb, exc);
}

The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.