Re: [Xen-devel] [PATCH 21/28] libxl: ocaml: add wrappers for poll

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2013-04-23 at 14:56 +0100, Dave Scott wrote:
> On 23/04/13 14:43, Ian Campbell wrote:
> > (aside: I'd really love it if tools/ocaml/libs/mmap could find a non-Xen
> > home too ;-))
> 
> I think I can arrange that.
> 
> In the mirage code we've settled on using OCaml 'bigarrays' [1] 
> (wrappers around C arrays) to pass around buffers, represent memory 
> pages etc. The OCaml standard library has the ability to mmap() stuff 
> and return a bigarray but there

Cool!

>  was an unfortunate bug where it assumed 
> the thing being mmap()ed also supported lseek() [2].

Not Cool!

> The bug was fixed in OCaml 4.00.0 so if we're happy to depend on that
> then we're ready to roll.

4.00.0 might be a bit bleeding edge to rely on outright. Ubuntu Raring
still only has 3.12.1. Debian has 4.00.1 in experimental but the next
stable release will have 3.12.x.

Would it be possible to turn the existing mmap thing into a compat
wrapper around the bigarrays for the case where the underlying ocaml is
buggy in this way?

Perhaps that is a lot of work and we should just shelve this
conversation for a couple of distro release cycles and reconsider making
this change then.

Ian.


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