Re: [PATCH v2 4/5] tools/ocaml/libs/xc: OCaml 5.0 compatibility

[Edwin Torok <edvin.torok@xxxxxxxxxx>]

This accidentally broke compatibility with OCaml 4.02.3, 
only realized when I went back to my Dune based build system which can 
automatically compile with multiple compiler versions.

See below for a patch for that. I've included this patch in the correct place 
(before the patch that breaks it) in the git repository at: 
https://github.com/edwintorok/xen/compare/private/edvint/public0


From 78a613cbb8db7033fe741488912f21b24eaaef56 Mon Sep 17 00:00:00 2001
Message-Id: 
<78a613cbb8db7033fe741488912f21b24eaaef56.1664295046.git.edvin.torok@xxxxxxxxxx>
From: =?UTF-8?q?Edwin=20T=C3=B6r=C3=B6k?= <edvin.torok@xxxxxxxxxx>
Date: Tue, 27 Sep 2022 17:06:57 +0100
Subject: [PATCH] tools/ocaml: fix compatibility with OCaml 4.02.3
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Signed-off-by: Edwin Török <edvin.torok@xxxxxxxxxx>
---
 tools/ocaml/libs/mmap/mmap_stubs.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tools/ocaml/libs/mmap/mmap_stubs.h 
b/tools/ocaml/libs/mmap/mmap_stubs.h
index 65e4239890..5c65cc86fb 100644
--- a/tools/ocaml/libs/mmap/mmap_stubs.h
+++ b/tools/ocaml/libs/mmap/mmap_stubs.h
@@ -30,4 +30,9 @@ struct mmap_interface
        int len;
 };

+/* for compatibility with OCaml 4.02.3 */
+#ifndef Data_abstract_val
+#define Data_abstract_val(v) ((void*) Op_val(v))
+#endif
+
 #endif
--
2.34.1

> On 27 Sep 2022, at 12:15, Edwin Török <edvin.torok@xxxxxxxxxx> wrote:
> 
> Follow the manual to avoid naked pointers:
> https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fv2.ocaml.org%2Fmanual%2Fintfc.html%23ss%3Ac-outside-head&amp;data=05%7C01%7Cedvin.torok%40citrix.com%7C4bf28f7a32074a49cdf008daa079a807%7C335836de42ef43a2b145348c2ee9ca5b%7C0%7C0%7C637998741634627105%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&amp;sdata=GU%2BbmB1ai0llQg0z5zWctzwW0ocUQUOHVlMxkeD3U0U%3D&amp;reserved=0
> 
> No functional change, except on OCaml 5.0 where it is a bugfix.
> 
> Signed-off-by: Edwin Török <edvin.torok@xxxxxxxxxx>
> ---
> tools/ocaml/libs/xc/xenctrl_stubs.c | 11 ++++++-----
> 1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/ocaml/libs/xc/xenctrl_stubs.c 
> b/tools/ocaml/libs/xc/xenctrl_stubs.c
> index 19335bdf45..7ff4e00314 100644
> --- a/tools/ocaml/libs/xc/xenctrl_stubs.c
> +++ b/tools/ocaml/libs/xc/xenctrl_stubs.c
> @@ -37,7 +37,7 @@
> 
> #include "mmap_stubs.h"
> 
> -#define _H(__h) ((xc_interface *)(__h))
> +#define _H(__h) *((xc_interface **) Data_abstract_val(__h))
> #define _D(__d) ((uint32_t)Int_val(__d))
> 
> #ifndef Val_none
> @@ -70,14 +70,15 @@ static void Noreturn failwith_xc(xc_interface *xch)
> CAMLprim value stub_xc_interface_open(void)
> {
>       CAMLparam0();
> -        xc_interface *xch;
> +     CAMLlocal1(result);
> 
> +     result = caml_alloc(1, Abstract_tag);
>       /* Don't assert XC_OPENFLAG_NON_REENTRANT because these bindings
>        * do not prevent re-entrancy to libxc */
> -        xch = xc_interface_open(NULL, NULL, 0);
> -        if (xch == NULL)
> +     _H(result) = xc_interface_open(NULL, NULL, 0);
> +     if (_H(result) == NULL)
>               failwith_xc(NULL);
> -        CAMLreturn((value)xch);
> +     CAMLreturn(result);
> }
> 
> 
> -- 
> 2.34.1
>