Re: [Xen-devel] [PATCH 1/2] make xen ocaml safe-strings compliant

[Christian Lindig <christian.lindig@xxxxxxxxxx>]

On 12/03/18 19:35, Michael Young wrote:

> Here is version 4 of the patch where I have replaced the uses of s with b
> where the patch changes it from string to bytes. I have also removed the
> two trailing spaces and changed stmp back to s.
>      Michael Young
> 0001-make-xen-ocaml-safe-strings-compliant.patch
>
>  From da088e4eef2bbea4be262e12db4c36960ff5145a Mon Sep 17 00:00:00 2001
> From: Michael Young<m.a.young@xxxxxxxxxxxx>
> Date: Mon, 12 Mar 2018 18:49:29 +0000
> Subject: [PATCH v4] make xen ocaml safe-strings compliant
>
> Xen built with ocaml 4.06 gives errors such as
> Error: This expression has type bytes but an expression was
>          expected of type string
> as Byte and safe-strings which were introduced in 4.02 are the
> default in 4.06.
> This patch which is partly by Richard W.M. Jones of Red Hat
> fromhttps://bugzilla.redhat.com/show_bug.cgi?id=1526703
> fixes these issues.
>
> v4: Where string s is now bytes, rename it to b.
>
> Signed-off-by: Michael Young<m.a.young@xxxxxxxxxxxx>
> ---
>   tools/ocaml/libs/xb/xb.ml        | 34 ++++++++++++++++++----------------
>   tools/ocaml/libs/xb/xb.mli       | 10 +++++-----
>   tools/ocaml/xenstored/logging.ml | 22 +++++++++++-----------
>   tools/ocaml/xenstored/stdext.ml  |  2 +-
>   tools/ocaml/xenstored/utils.ml   | 20 ++++++++++----------
>   5 files changed, 45 insertions(+), 43 deletions(-)
Reviewed-by: Christian Lindig<christian.lindig@xxxxxxxxxx>

This patch is good to go. One caveat, though: the conversion between bytes and 
strings
is not just a cast but involves copying and thus has a performance cost which we
want to keep in mind. The OCaml low-level libraries like Unix.read return 
(mutable) bytes,
but most code expects (immutable) strings. I believe that it would be difficult 
to avoid
this in the long run and this patch is the right way to go.

-- Christian
 

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