Re: [PATCH v1 0/6] tools/ocaml/xenstored: simplify code

[Christian Lindig <christian.lindig@xxxxxxxxxx>]

I see little reason to support old OCaml releases and requiring OCaml 4.06 
would be fine with me but I assume that the project might have its own ideas 
about this.

________________________________________
From: Edwin Torok
Sent: 18 August 2020 08:28
To: Christian Lindig; xen-devel@xxxxxxxxxxxxxxxxxxxx
Cc: Ian Jackson; dave@xxxxxxxxxx; wl@xxxxxxx
Subject: Re: [PATCH v1 0/6] tools/ocaml/xenstored: simplify code

On Mon, 2020-08-17 at 14:56 +0200, Christian Lindig wrote:
> This all looks good - I left a small comment on one of the patches
> and I agree that this needs testing. I also wonder about
> compatibility with earlier OCaml releases that we support but I see
> no real obstacles.
>

I've developed the series using OCaml 4.08.1. I think the newest
feature I used was Map.update (OCaml 4.06, nearly 3 years ago).
Looking through https://repology.org/project/ocaml/versions I'm not
sure if we can require more than 4.05 though.
The README in Xen doesn't specify a minimum version, but configure
checks for >=4.02.

I can try to backport my series to OCaml 4.05 (to use Map.find_opt
instead of Map.update) and update the configure check to require 4.05.
It would be possible to backport even further to 4.02 by introducing
additional inefficiencies (Map.mem + Map.find would traverse the map
twice, and Map.find on its own would raise an exception on Not found,
which is more costly than returning None in Map.find_opt), I'd avoid
doing that.

Xen's CI from automation might need some updates to use latest stable
versions:
* Fedora 29 is EOL, should use at least Fedora 31
* Debian Jessie is EOL. Stretch is present, but Buster is missing

Best regards,
--Edwin