This package can be used to run OCaml packages with the check for 'naked pointers' enabled. A naked pointer is a pointer outside the OCaml heap without a valid header, which is valid in OCaml 4.x, but forbidden in the multicore OCaml 5.x runtime. The nnpchecker prints warnings to standard error with the address that contains the naked pointer, the naked pointer and the reason why the warning was raised. See [https://discuss.ocaml.org/t/ann-a-dynamic-checker-for-detecting-naked-pointers/5805] for more details on the operation of the naked pointer checker.
By convention, the opam repository adds conflicts to OCaml packages that violate the naked pointer rule. This means that if you install this package, you can find the subset of packages that are compatible with OCaml 5. If you spot any violations of the nnpchecker on packages, then please consider submitting a pull request to the ocaml/opam-repository that adds a conflict against the violating package against this one.