libctypes-ocaml-dev binary package in Ubuntu Bionic amd64

 The ocaml-ctypes library makes it possible to call C functions
 directly from OCaml without writing or generating C code. The core
 of the library is a set of combinators for describing C types --
 scalars, functions, structs, unions, arrays, and pointers to values
 and functions. Type descriptions can then be used to bind native
 functions and values.
 .
 This package contains all the development stuff you need to use
 ocaml-ctypes.

Source package