Function make_random_loop_control

src/StatementFor.cpp:70–127

* Randomly determine the parameters for a counting loop: initial value, limit * value, increment value, test operator, and increment operator. */

 * value, increment value, test operator, and increment operator.
 */
static void
make_random_loop_control(int &init, int &limit, int &incr,
						 eBinaryOps &test_op,
						 eAssignOps &incr_op,
						 bool iv_signed)
{
	// We don't have to put error guards here because we are trying
	// to get pure random numbers, and in this case, we cannot get
	// errors
	init  = pure_rnd_flipcoin(50) ? 0 : (pure_rnd_upto(60)-30);
	limit = iv_signed ? (pure_rnd_upto(60) - 30) : (pure_rnd_upto(60) + 1);

	eBinaryOps t_ops[] = { eCmpLt, eCmpLe, eCmpGt, eCmpGe, eCmpEq, eCmpNe };
	test_op = t_ops[pure_rnd_upto(sizeof(t_ops)/sizeof(*t_ops))];
	ERROR_RETURN();

	if (pure_rnd_flipcoin(50)) {
		ERROR_RETURN();
		// Do `+=' or `-=' by an increment between 0 and 9 inclusive.
		// make sure the limit can be reached without wrap-around
		incr = pure_rnd_upto(10);
    // avoid an infinite loop due to inexact division, e.g,
    // init = 0, limit = 3, step = 2, test_op = eCmpNe
    if (test_op == eCmpNe && incr > 1)
      limit = (limit - init) / incr * incr + init;
    incr_op = (limit >= init) ? eAddAssign : eSubAssign;
    if (incr == 0) incr = 1;

    // A rare case that could cause wrap around: distance between init
    // and limit is multiple of incr, and the incr goes to wrong direction.
    // For example: init = 8, limit = 1, incr = -7. test_op is >=
    if (CGOptions::fast_execution() && (limit - init) % incr == 0 && 
      (test_op == eCmpGe || test_op == eCmpLe)) {
      limit = (incr_op == eAddAssign) ? limit + 1 : limit - 1;
    }
	} else {
		ERROR_RETURN();
		// Do `++' or `--', pre- or post-.
		// make sure the limit can be reached without wrap-around
		if ((limit < init) || ((limit == init) && (test_op == eCmpGe))) {
			incr_op = pure_rnd_flipcoin(50) ? ePreDecr : ePostDecr;
		} else {
			incr_op = pure_rnd_flipcoin(50) ? ePreIncr : ePostIncr;
		}
		if (((incr_op == ePreIncr) && !CGOptions::pre_incr_operator())
			|| ((incr_op == ePostIncr) && !CGOptions::post_incr_operator())) {

			incr_op = eAddAssign;
		}
		if (((incr_op == ePreDecr) && !CGOptions::pre_decr_operator())
			|| ((incr_op == ePostDecr) && !CGOptions::post_decr_operator())) {

			incr_op = eSubAssign;
		}
		incr = 1;
	}
	ERROR_RETURN();
}