BFM-decomp/cookbook/C0399.md

§358 (sharpens §333) — AN UNREFERENCED FIXED-SIZE AGGREGATE LOCAL IS LOAD-BEARING (P31 S68; same function)

A 32-byte aggregate local declared before pos and never referenced anywhere in the body is what makes the frame -0x58 and places pos at sp+0x30. expand_decl slots every fixed-size aggregate whether or not it is used.

§333 says frame size is set by DECLARED aggregates. This adds that the aggregate need not be referenced at all — which turns it from a constraint you work around into a knob you can turn. (The remaining 13 on that function were §3-T2 statement order: call → i=0 → mtx → colp.)