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[TheLortex]

In the mirage+dune series of PR (mirage/mirage#969).

Workspace flags

Use :standard to get the flags from the build workspace. This means xen/unix flags are automatically set up and we don't need to know about backends anymore.

Compatibility stubs

We keep io-page-xen and io-page-unix in order not to have to modify every revdep.

[TheLortex]

@samoht rebased according to your review !

[samoht]

Just to fully understand: the only thing that this PR is doing is moving the compilation of C stubs into the main package, so that's dune could cross-compile everything more easily. But this doesn't change anything for users of the library, right?

[TheLortex]

Yes, instead of having io-page to know about the different backends (xen, unix), the task is delegated to dune which will automatically compile the C stubs with the correct flags.

[samoht]

But then, I am not sure to understand why we need to keep io-page-unix and io-page-xen : they will not work properly if people didn't configure their workspace to do cross-compilation.

I think it's just better to remove these and add bounds to the rev-dependencies. I'm fine doing this myself.

[TheLortex]

It's just because revdeps still depend on io-page-xen|unix and I haven't taken the time to look at them. For xen these are: mirage-block-xen, mirage-console-xen, mirage-net-xen, mirage-profile-xen, mirage-tcpip-xen, mirage-xen, netchannel. For unix there is even more..

[samoht]

I can help fixing the revdeps. I think it's better to just remove these packages if they are not useful (and if they won't be able to link with existing unikernels using ocamlbuild anyway as they will not be cross-compiled correctly).

[samoht]

See ocaml/opam-repository#14621 for the revdeps fixes

[samoht]

Now that ocaml/opam-repository#14621 is merged, I've pushed to the PR to remove io-page-unix and io-page-xen completely.

[avsm]

This is fine, but let's please document clearly in the CHANGES file that the reason it works is that existing ocamlbuild setups will pickup io-page-xen/unix, whereas mirage4 won't need them at all. Otherwise it's not clear what happens to old packages.

[hannesm]

existing ocamlbuild setups will pickup io-page-xen/unix

I'd suggest to add a conflict in the opam file of the to-be-released io-page of the form:
conflicts: [ "mirage-runtime" {< "4.0.0"} ] (I guess mirage-runtime is the most sensible package (since it is depended on by every unikernel), but of course mirage-types or mirage-types-lwt could be used as well).