Seems odd that no ancient chinese fortification had any machicolations or murder holes. How did they deal with attackers that already reached the base of the walls?
Note that typical Chinese fortification walls are sloped (the usual construction is rammed earth, often with a brick or stone facing, and the walls are thicker at the base than at the top), and things dropped through machicolations would roll/run down the sloping walls rather than dropping directly onto the attackers.
The usual method to deal with attackers at the base of the wall was bastions, outward-projecting extensions from the wall. For example, bastions along the Beijing city walls c. 1900:
Ideally, the distance between bastions is at most the effective range of the weapons used by the defenders. If bows, then they should be at most an effective bowshot apart, so that defenders on one bastion can shoot attackers at the foot of the adjacent bastions.
Chinese bastions are typically rectangular. This is often regarded as an inferior design, with triangular and pentagonal bastions being best, and semicircular/half-oval next best. This is because the outer wall of a rectangular bastion can offer dead ground for the attacker. However, pre-gunpowder, rectangular bastions are common, since they allow a numerically strong force of defenders to repel escalade on the outer face, whereas a triangular/pentagonal bastion only allows a small force at the tip. In China, we see rectangular bastions continuing in use to the end of the Imperial era.
Apart from the dependence on rectangular bastions, one also sees bastions that are too far apart (also outside China). This is a cost-cutting measure - bastions are expensive, and the budget-minded are tempted to build fewer of them. However, good-quality fortifications had well-spaced (i.e., close) bastions. For example, the short edge of the city wall of Xi'an:
has a little over 20 bastions, over a length of under 3km, so the spacing is under 150m.
References:
Photo of Xi'an city walls from https://www.navjot-singh.com/navjots-blog/my-travels-in-xian-a-city-with-over-3000-years-of-rich-chinese-history-and-culture
For a review of bastions in ancient fortifications, see Keeley, L., Fontana, M., & Quick, R. (2007), "Baffles and Bastions: The Universal Features of Fortifications", Journal of Archaeological Research 15(1), 55-95, http://www.jstor.org/stable/41053234
