Comment by avsm | Hacker News Reader

Comment by avsm | Hacker News Reader

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This is indeed on our development list for this winter to integrate more. Over in MirageOS (mirage.io), we've been working hard on getting RISC-V support in shape, so we can build unikernels for bare metal embedded devices with a simple "dune build @riscv-solo5".

As part of that work, a few things are going on:

- use "dune workspaces" (essentially a cross compilation context) to build all C bindings in OCaml packages with custom CFLAGS/LDFLAGS. Ongoing work here: https://github.com/mirage/mirage/pull/1153

- upstream in OCaml, the core developers have specced out the design for integrating cross-compilation more naturally into the compiler.

- OCaml 4.11.0 has just been released with a native code RISC-V backend (and of course has had ARM for years).

Mirage doesn't really use OpenEmbedded or Yocto, but I expect it should be straightforward to embed the workflow in there once it's stable upstream in Mirage itself. Any pointers to something I should read about how to get involved in Yocto?

There's a non-upstream OpenEmbedded layer for building OCaml components, but it jumps through hoops to coordinate OCaml toolchain with upstream OE releases, https://github.com/OpenXT/meta-openxt-ocaml-platform

This could be generalized to create an upstream OE layer that uses the upcoming cross-compiling improvements from upstream Ocaml, which would then enable MirageOS unikernels in OE meta-virtualization, https://layers.openembedded.org/layerindex/branch/master/lay.... RISC-V support is in early stages for meta-virt, Western Digital added some support.

Intro to meta-virt: https://youtube.com/watch?feature=emb_title&v=fIbWvrlWJYg

Intro to Yocto: https://elinux.org/images/a/a8/Getting_Started_with_Embedded...

Meta-virt mailing list would be a good place for discussion, https://lists.yoctoproject.org/g/meta-virtualization

Very handy, thanks. I notice that the openxt-ocaml-platform repo uses ocamlbuild/ocamlfind. Life should get a lot easier when we move that to use ocaml/dune directly -- cross-compilation really needs a lot of help from the build system, and dune is moving fast to support these workflows.

Hopefully there can be a way to use ocaml/dune directly without importing "everything" into each per-component build tree. OE best practices employ per-recipe sysroots for building each component, where a minimal set of dependencies is present for the build environment. This helps with reproducible builds and generation of manifests for supply chain integrity.

Yes that should be fine. For incremental installation, there is a `dune build -x` which builds using a particular cross-compilation toolchain. MirageOS builds everything in one go, but it can be broken up too (as opam itself does).

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