Install runtime headers for mirage-xen. #102
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- Provides C code with headers that match the minimal libc and OCaml functions they will be linked against.
Do you have an example code doing that somewhere? |
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The XSM bindings are in this repository (still very much a work in progress): |
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We should definitely do this; however, shouldn't the headers be installed from https://github.com/mirage/mirage-xen-minios instead? For instance, the hardcoding of |
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now that I'm back in berlin, expect my changes/way to get gmp, nocrypto, tls to work on my cubieboard later today! |
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great! dont forget to |
Those are installed as well. It turns out (at least in my case where I'm writing C stubs that call Xen hypercalls) that you need both sets of headers. My experience using only the minios headers was that I couldn't compile the OCaml headers due to missing includes (like string.h). Also, without installing mirage-xen's headers, aren't we getting the OCaml headers from the host compiler rather than the target? |
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Yeah, these the mirage-xen headers are extracted from the original merged minios headers. So we do need to have a minimal set to provide the bridge between minios and libc (for instance, we grab printf from musl-libc, and could do a similar job for string.h). There's no issue with target/host, since OCaml doesn't do cross-compilation :) Luckily, the code ocamlopt produces is quite independent since all C symbols are resolved at link time and are explicitly specified in the |
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@talex5 is on vacation for a couple of weeks btw, so if this one isn't too urgent it would be good to wait for him to come back to comment on the thread too, so we can make sure this one's done properly. |
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Seems reasonable to me (except it looks like it installs the whole of runtime/ocaml, rather than just the headers). |
Now that Mirage contains only a very minimal libc, I'd like to suggest we install the headers for those libc functions and the OCaml runtime somewhere where C stubs can find it.
C code is going to be linked against the functions regardless---given that, it seems prudent to allow them to have access to their headers as well. Otherwise, libraries will need to include their own libc definitions which may be incompatible or clash with those defined by the Mirage runtime.
This patch installs runtime headers into $(OPAM_PREFIX)/include/mirage-xen, alongside the minios headers. With this change, I've successfully built an add-on module to mirage that exposes additional hypercalls via OCaml.