Constant MAX_OPERATIONS 

const MAX_OPERATIONS: u32 = 1_000_000;

Maximum number of operations that can be processed during charstring evaluation.

HarfBuzz limits this to 200,000 (https://github.com/harfbuzz/harfbuzz/blob/a6357ca3f7e73165ba8b201b65f1130059e34255/src/hb-limits.hh#L108) and threat analysis suggested 2,000,000 so a value of 1,000,000 was chosen to match our instruction limit for the TrueType interpreter.

FreeType only limits depth, not number of operations.