On Tue, Jan 21, 2014 at 9:48 PM, Anil Madhavapeddy <a...@recoil.org> wrote:
> On 21 Jan 2014, at 21:31, David Scott <scott...@gmail.com> wrote:
>
> NB: I think I'm hitting an opam 1.1.0-beta bug where "mirage-types"
> optionally depends on "lwt & ipaddr"; some other package depends on "lwt";
> but "ipaddr" is not being demanded. Anyone else seeing this? Perhaps I've
> misunderstood the meaning of depopts in opam. A workaround is just to
> install "ipaddr" first.
>
>
> The intention here is to have:
>
> - a 'mirage-types' package that is completely dependency free, and only
> has module type definitions with completely abstract types.
> - a 'mirage-types.lwt' package which specializes the above types with some
> concrete common defaults, specifically Lwt for IO and Cstruct for buffer,
> Ipaddr.V4.t for ipaddr. Because these are concrete types in the module
> signature, you now need those libraries installed to get the cmi files for
> them.
>
> The OPAM line of:
>
> depopts: [ ("lwt" & "cstruct" & "ipaddr") ]
>
> means that if all three of the packages are present, then an optional
> dependency (the mirage-types.lwt) will be compiled. However, upstream
> users of mirage-types.lwt will thus need to explicitly depend on
> lwt/cstruct/ipaddr to ensure that mirage-types.lwt will actually be present.
>
Ah ok. In my case the BLOCK signature is being used by mirage-block-xen, so
I guess I should explicitly add ipaddr to its depends (I'm sure lwt and
cstruct are already there). Pity I can't say it depends on
'mirage-types.lwt' -- I guess that would require yet another package.
I notice the new mirage-types.lwt will try to build IFF 'lwt' is present:
https://github.com/avsm/mirage/blob/split-libs/build#L3
Perhaps we should change this to IFF 'lwt & cstruct & ipaddr' so the error
manifests as a 'mirage-types.lwt' is missing higher up the dependency chain
where the missing dependency on 'ipaddr' is?
Cheers,
Dave
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