What I had specifically in mind definitely wasn't using OCaml or Menhir, but that's a very useful resource, as is the associated paper, "A simple, possibly correct LR parser for C11", https://jhjourdan.mketjh.fr/pdf/jourdan2017simple.pdf

This is closer to what I remember, but I'm not convinced it's what I had in mind, either: https://github.com/edubart/lpegrex/blob/main/parsers/c11.lua It uses LPeg's match-time capture feature (not a pure PEG construct) to dynamically memorize typedef's and condition subsequent matches. In fact, it's effectively identical to what C11Parser is doing, down to the two dynamically invoked helper functions: declare_typedefname/is_typedefname vs set_typedef/is_typedef. C11Parser and the paper are older, so maybe the lpegrex parser is derivative. (And probably what I had in mind, if not lpegrex, was derivative, too.)