[conf-gmp] [depext] 32bit dev package for Debian

[ejgallego]

I think this should be fine, and makes the zarith opam package build with a 32bit OCaml on Ubuntu / Debian.

In the case of a very old distro, this should be OK as libgmp-dev:i386 is rewritten to libgmp-dev.

[jmid]

IIUC, there are two ways to support 32-bit:

• there's running on a good old x86 32-bit processor (or in a Docker container simulating it) or
• there's multi-arch support allowing to compile and run 32-bit executables on a 64-bit "amd64/x86_64" processor

It seems to me, that this PR offers conf-gmp packages for the latter, while the CI is failing on the former with

• x86_32-ocaml-4.14 - conf-gmp.4 (failed: [SKIP] Package not available)
• x86_32-ocaml-5.2 - conf-gmp.4 (failed: [SKIP] Package not available)

I can't think of a good way to distinguish the two 32bit modes unfortunately 🤷
ocaml-option-32bit for the latter uses gcc -m32 as its C-compiler - but that is definitely hackish! 😅

[ejgallego]

Hi @jmid , thanks for the analysis. I would believe this solution would have worked on case 1 too as in this case libgmp-dev:i386 is an alias for libgmp-dev, but indeed maybe we need to be more careful.

[ejgallego]

I see, so indeed it is depexts who doesn't understand the :i386 prefix, apt should.

I wonder if it is worth patching depext to understand this?

Maybe @kit-ty-kate has some advice on this?

This PR is anyways of priority "wishlisth" IMHO, so happy to close it, the motivation was to make CI work better with setup-ocaml action in our 32bit CI builds. FYI, we keep these builds due to js_of_ocaml.