15:37 <mk__> Is there any technique to create a Mirage unikernel for xen, with code dependency on C libraries?

16:01 <dinosaure> mk__: it's depends about your C library

16:02 <dinosaure> I mean, if you C library has some syscall, you should have some trouble

16:02 <dinosaure> but for some "agnostic to the system" C code, it's possible (and it is the case for some MirageOS libraries)

16:09 <mk__> I think (not sure), it is agnostic to the system. In the case of being agnostic, how is it possible to do it?

16:10 <mk__> for instance, ocaml tensorflow?

16:38 <dinosaure> hmmhmm, I see

16:39 <dinosaure> so first, any C libraries for xen needs to be compiled with some special flags: https://github.com/mirage/checkseum/blob/0.0.9/src-c/native/xen/dune

16:40 <dinosaure> you can get flags with pkg-config: https://github.com/mirage/checkseum/blob/0.0.9/src-c/native/xen/cflags.sh

16:42 <dinosaure> then, your library (we still are outside your unikernel) must provide a special META file

16:43 <dinosaure> this META file should provide at least for xen this line: https://github.com/mirage/checkseum/blob/0.0.9/META.checkseum.template#L3

16:43 <dinosaure> (the other line is for hvt/kvm/solo5)

16:43 <dinosaure> so, the *.a is the C library compiled with right flags

16:44 <dinosaure> then, in your unikernel, you should not update anythin where ocamlbuild/ocamlfind will select automagically your *.a

16:45 <dinosaure> it's little bit complex currently (MirageOS 4 should be easier) but checkseum.0.0.9 is a good example of how to integrate C code for an unikernel

16:46 <dinosaure> (checkseum go further and uses cmx trick but it's orthogonal to your goal :) )

16:47 <mk__> That is actually nice! I will try it soon, and will get back to this channel if it didn't work well

16:48 <dinosaure> then, at the link step of your unikernel, you will see what is missing (about C stdlib) :D

16:50 <mk__> So, how to fix those link problems?

16:51 <dinosaure> reimplement them/delete them :d

16:52 <dinosaure> for example, if you look into checkseum, we redefine some type like size_t/ptrdiff_t which are not available

16:53 <dinosaure> in other side, it's better to try to delete what you don't use (a concrete task here: https://github.com/mirage/ocaml-freestanding/issues/60)

16:54 <mk__> is there any documentation on how to write META file? For instance, what xen_linkopts and freestanding_linkopts are?

16:59 <dinosaure> mk__: it's trick :D and about how to write a META, I read some to learn :/