From their github https://github.com/ocaml/camlp4/blob/trunk/README.md Camlp4 was a software system for writing extensible parsers for programming languages. Since August 2019, Camlp4 is no longer maintained.
...and now, after ocaml-4.09.0 bump we're screwed because all revdeps fail: >>> Configuring source in /tmp/portage/dev-ml/camlp4-4.05_p1/work/camlp4-4.05-1 ... This version of Camlp4 is for OCaml 4.05 but you are using OCaml 4.09.0. If building Camlp4 directly from git, use the 4.09 branch.
(In reply to Michał Górny from comment #1) > ...and now, after ocaml-4.09.0 bump we're screwed because all revdeps fail: > > >>> Configuring source in /tmp/portage/dev-ml/camlp4-4.05_p1/work/camlp4-4.05-1 ... > This version of Camlp4 is for OCaml 4.05 but you are using OCaml 4.09.0. > If building Camlp4 directly from git, use the 4.09 branch. bumped