Re: [Xen-devel] [PATCH] tools/ocaml: Fix build error with Arch Linux

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

On Sat, Oct 26, 2019 at 02:21:10AM +0300, Petre Pircalabu wrote:
> gcc (GCC) 9.2.0 complains:
> 
> xentoollog_stubs.c: In function ‘stub_xtl_ocaml_vmessage’:
> xentoollog_stubs.c:93:16: error: initialization discards ‘const’ qualifier 
> from pointer target type [-Werror=discarded-qualifiers]
>    93 |  value *func = caml_named_value(xtl->vmessage_cb) ;
>       |                ^~~~~~~~~~~~~~~~

Hi Petre,

Thanks for the patch, it looks fine. However it would be nice to add
some more context on why gcc complains. A quick search seems to lead to
https://github.com/ocaml/ocaml/commit/4f03a1467d29cf587df5a191830f1525506ee0e3
    "Make caml_named_value return a const value*"
which change the prototype of caml_named_value.

With the commit message changed:
Reviewed-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>

CC Jürgen, I think it would be nice to have the build fix in the
release.

Cheers.


> Signed-off-by: Petre Pircalabu <ppircalabu@xxxxxxxxxxxxxxx>
> ---
>  tools/ocaml/libs/xentoollog/xentoollog_stubs.c |  4 ++--
>  tools/ocaml/libs/xl/xenlight_stubs.c           | 20 ++++++++++----------
>  2 files changed, 12 insertions(+), 12 deletions(-)
> 
> diff --git a/tools/ocaml/libs/xentoollog/xentoollog_stubs.c 
> b/tools/ocaml/libs/xentoollog/xentoollog_stubs.c
> index aadc3d1..1f73f26 100644
> --- a/tools/ocaml/libs/xentoollog/xentoollog_stubs.c
> +++ b/tools/ocaml/libs/xentoollog/xentoollog_stubs.c
> @@ -90,7 +90,7 @@ static void stub_xtl_ocaml_vmessage(struct 
> xentoollog_logger *logger,
>       CAMLparam0();
>       CAMLlocalN(args, 4);
>       struct caml_xtl *xtl = (struct caml_xtl*)logger;
> -     value *func = caml_named_value(xtl->vmessage_cb) ;
> +     const value *func = caml_named_value(xtl->vmessage_cb) ;
>       char *msg;
>  
>       if (func == NULL)
> @@ -120,7 +120,7 @@ static void stub_xtl_ocaml_progress(struct 
> xentoollog_logger *logger,
>       CAMLparam0();
>       CAMLlocalN(args, 5);
>       struct caml_xtl *xtl = (struct caml_xtl*)logger;
> -     value *func = caml_named_value(xtl->progress_cb) ;
> +     const value *func = caml_named_value(xtl->progress_cb) ;
>  
>       if (func == NULL)
>               caml_raise_sys_error(caml_copy_string("Unable to find 
> callback"));
> diff --git a/tools/ocaml/libs/xl/xenlight_stubs.c 
> b/tools/ocaml/libs/xl/xenlight_stubs.c
> index ff16b87..1181971 100644
> --- a/tools/ocaml/libs/xl/xenlight_stubs.c
> +++ b/tools/ocaml/libs/xl/xenlight_stubs.c
> @@ -75,7 +75,7 @@ static void failwith_xl(int error, char *fname)
>  {
>       CAMLparam0();
>       CAMLlocal1(arg);
> -     static value *exc = NULL;
> +     static const value *exc = NULL;
>  
>       /* First time around, lookup by name */
>       if (!exc)
> @@ -424,7 +424,7 @@ void async_callback(libxl_ctx *ctx, int rc, void 
> *for_callback)
>       caml_leave_blocking_section();
>       CAMLparam0();
>       CAMLlocal2(error, tmp);
> -     static value *func = NULL;
> +     static const value *func = NULL;
>       value *p = (value *) for_callback;
>  
>       if (func == NULL) {
> @@ -1133,7 +1133,7 @@ value stub_libxl_xen_console_read_start(value ctx, 
> value clear)
>  
>  static void raise_eof(void)
>  {
> -     static value *exc = NULL;
> +     static const value *exc = NULL;
>  
>       /* First time around, lookup by name */
>       if (!exc)
> @@ -1274,7 +1274,7 @@ int fd_register(void *user, int fd, void 
> **for_app_registration_out,
>       CAMLparam0();
>       CAMLlocalN(args, 4);
>       int ret = 0;
> -     static value *func = NULL;
> +     static const value *func = NULL;
>       value *p = (value *) user;
>       value *for_app;
>  
> @@ -1317,7 +1317,7 @@ int fd_modify(void *user, int fd, void 
> **for_app_registration_update,
>       CAMLparam0();
>       CAMLlocalN(args, 4);
>       int ret = 0;
> -     static value *func = NULL;
> +     static const value *func = NULL;
>       value *p = (value *) user;
>       value *for_app = *for_app_registration_update;
>  
> @@ -1356,7 +1356,7 @@ void fd_deregister(void *user, int fd, void 
> *for_app_registration)
>       caml_leave_blocking_section();
>       CAMLparam0();
>       CAMLlocalN(args, 3);
> -     static value *func = NULL;
> +     static const value *func = NULL;
>       value *p = (value *) user;
>       value *for_app = for_app_registration;
>  
> @@ -1398,7 +1398,7 @@ int timeout_register(void *user, void 
> **for_app_registration_out,
>       CAMLlocal2(sec, usec);
>       CAMLlocalN(args, 4);
>       int ret = 0;
> -     static value *func = NULL;
> +     static const value *func = NULL;
>       value *p = (value *) user;
>       struct timeout_handles *handles;
>  
> @@ -1450,7 +1450,7 @@ int timeout_modify(void *user, void 
> **for_app_registration_update,
>       CAMLlocal1(for_app_update);
>       CAMLlocalN(args, 2);
>       int ret = 0;
> -     static value *func = NULL;
> +     static const value *func = NULL;
>       value *p = (value *) user;
>       struct timeout_handles *handles = *for_app_registration_update;
>  
> @@ -1566,7 +1566,7 @@ void event_occurs(void *user, libxl_event *event)
>       CAMLparam0();
>       CAMLlocalN(args, 2);
>       struct user_with_ctx *c_user = (struct user_with_ctx *) user;
> -     static value *func = NULL;
> +     static const value *func = NULL;
>  
>       if (func == NULL) {
>               /* First time around, lookup by name */
> @@ -1589,7 +1589,7 @@ void disaster(void *user, libxl_event_type type,
>       CAMLparam0();
>       CAMLlocalN(args, 4);
>       struct user_with_ctx *c_user = (struct user_with_ctx *) user;
> -     static value *func = NULL;
> +     static const value *func = NULL;
>  
>       if (func == NULL) {
>               /* First time around, lookup by name */
> -- 
> 2.7.4
> 
> 
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-- 
Anthony PERARD

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