Install ocaml_integers.h

[jonahbeckford]

Problem

I encountered the following while trying to cross-compile the luv package (my own setup / not opam-monorepo / but using your Dune-ified ocaml-ctypes package):

jonah@DK-MCHO-Mac-M1-A luv % dune build -x darwin_x86_64 @install
        bash src/c/generate_types_step_2.exe (exit 1)
(cd _build/default/src/c && /bin/bash config/compile_c.sh generate_types_step_2.c /private/tmp/dckbuild/darwin_x86_64/Debug/dksdk/_opam/lib/ctypes generate_types_step_2.exe clang -arch arm64 -O2 -fno-strict-aliasing -fwrapv -arch arm64)
In file included from generate_types_step_2.c:8:
In file included from /private/tmp/dckbuild/darwin_x86_64/Debug/dksdk/_opam/lib/ctypes/ctypes_cstubs_internals.h:13:
/private/tmp/dckbuild/darwin_x86_64/Debug/dksdk/_opam/lib/ctypes/ctypes_primitives.h:16:10: fatal error: 'ocaml_integers.h' file not found

Solution

The Makefile-based version simply copies that ocaml_integers.h file from the integers package. This PR does the equivalent in Dune.

Confer: https://github.com/ocamllabs/ocaml-ctypes/blob/9048ac78b885cc3debeeb020c56ea91f459a4d33/Makefile#L87

Note: If this is the wrong upstream for Dune-ified ocaml-ctypes, please tell me where to submit the PR. I located it from https://github.com/dune-universe/opam-overlays/blob/master/packages/ctypes/ctypes.0.17.1%2Bdune/opam

[avsm]

Thanks Jonah! I think this is the right fix, and it was raised in the comments on yallop#588 as well. @TheLortex, does your yaml problem go away if you layer this fix to the dune-universe/opam-overlays ctypes override?

[TheLortex]

This helps a lot indeed. There remains two small patches to do in ocaml-yaml:

• in the discover script is given the dune variable %{lib:ctypes:ctypes_cstubs_internals.h}, but it can be a relative path so it has to go through Unix.realpath before being written into the -I ... C flags.
• the ctypes-cflags rule that uses the discover script has to declare the headers files of the ctypes package as dependencies, otherwise they are not imported in the _build folder where they are included from: so (deps (package ctypes)) has to be added. This works in monorepos, but not in opam before dune 3.0.