Camlp4 is still very much around and maintained out of tree, and will work in the next release of OCaml (https://github.com/ocaml/camlp4 https://github.com/ocam

Camlp4 is still very much around and maintained out of tree, and will work in the next release of OCaml (https://github.com/ocaml/camlp4 https://github.com/ocaml/camlp4). Extension points are intended to be simpler and more easily integrated into editors for the common case, but you can still use camlp4 for extensions that genuinely extend the OCaml grammar.