[Xen-devel] Tools build failure with gcc-9.2.1

[Xen-devel] Tools build failure with gcc-9.2.1

[Dario Faggioli]

[-- Attachment #1: Type: text/plain, Size: 1393 bytes --]

Hello,

Are the following errors (and more similar ones):

 CC       xenctrl_stubs.o
In file included from /usr/lib64/ocaml/caml/alloc.h:24,
                 from xenctrl_stubs.c:22:
xenctrl_stubs.c: In function 'stub_xc_vcpu_context_get':
/usr/lib64/ocaml/caml/mlvalues.h:265:24: error: passing argument 1 of 'memcpy' discards 'const' qualifier from pointer target type [-Werror=discarded-qualifiers]
  265 | #define String_val(x) ((const char *) Bp_val(x))
      |                       ~^~~~~~~~~~~~~~~~~~~~~~~~~
xenctrl_stubs.c:502:9: note: in expansion of macro 'String_val'
  502 |  memcpy(String_val(context), (char *) &ctxt.c, sizeof(ctxt.c));
      |         ^~~~~~~~~~
In file included from xenctrl_stubs.c:30:
/usr/include/string.h:43:14: note: expected 'void * restrict' but argument is of type 'const char *'
   43 | extern void *memcpy (void *__restrict __dest, const void *__restrict __src,
      |              ^~~~~~

When building with:

gcc version 9.2.1 20200306 [revision c5edde44f5b17b4891f17a63517f355bbf89e7d3] (SUSE Linux) 

Already known and being dealt with?

Regards
-- 
Dario Faggioli, Ph.D
http://about.me/dario.faggioli
Virtualization Software Engineer
SUSE Labs, SUSE https://www.suse.com/
-------------------------------------------------------------------
<<This happens because _I_ choose it to happen!>> (Raistlin Majere)


[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

Re: [Xen-devel] Tools build failure with gcc-9.2.1

[Julien Grall]

On 25/03/2020 09:40, Dario Faggioli wrote:
> Hello,

Hi Dario,

> 
> Are the following errors (and more similar ones):
> 
>   CC       xenctrl_stubs.o
> In file included from /usr/lib64/ocaml/caml/alloc.h:24,
>                   from xenctrl_stubs.c:22:
> xenctrl_stubs.c: In function 'stub_xc_vcpu_context_get':
> /usr/lib64/ocaml/caml/mlvalues.h:265:24: error: passing argument 1 of 'memcpy' discards 'const' qualifier from pointer target type [-Werror=discarded-qualifiers]
>    265 | #define String_val(x) ((const char *) Bp_val(x))
>        |                       ~^~~~~~~~~~~~~~~~~~~~~~~~~
> xenctrl_stubs.c:502:9: note: in expansion of macro 'String_val'
>    502 |  memcpy(String_val(context), (char *) &ctxt.c, sizeof(ctxt.c));
>        |         ^~~~~~~~~~
> In file included from xenctrl_stubs.c:30:
> /usr/include/string.h:43:14: note: expected 'void * restrict' but argument is of type 'const char *'
>     43 | extern void *memcpy (void *__restrict __dest, const void *__restrict __src,
>        |              ^~~~~~
> 
> When building with:
> 
> gcc version 9.2.1 20200306 [revision c5edde44f5b17b4891f17a63517f355bbf89e7d3] (SUSE Linux)
> 
> Already known and being dealt with?

I suspect you have a new version of Ocaml built with -safe-string as per 
[1], String_Val() will return (const char *) rather than (char *).

I am looking at writing a patch for it and send it to xen-devel.

Cheers,

[1] https://github.com/ocaml/ocaml/pull/1274

> 
> Regards
> 

-- 
Julien Grall

Re: [Xen-devel] Tools build failure with gcc-9.2.1

[Dario Faggioli]

[-- Attachment #1: Type: text/plain, Size: 1180 bytes --]

On Sun, 2020-03-29 at 18:19 +0100, Julien Grall wrote:
> On 25/03/2020 09:40, Dario Faggioli wrote:
> > /usr/include/string.h:43:14: note: expected 'void * restrict' but
> > argument is of type 'const char *'
> >     43 | extern void *memcpy (void *__restrict __dest, const void
> > *__restrict __src,
> >        |              ^~~~~~
> > 
> > When building with:
> > 
> > gcc version 9.2.1 20200306 [revision
> > c5edde44f5b17b4891f17a63517f355bbf89e7d3] (SUSE Linux)
> > 
> > Already known and being dealt with?
> 
> I suspect you have a new version of Ocaml built with -safe-string as
> per 
> [1], String_Val() will return (const char *) rather than (char *).
> 
Yep, I checked in the ocaml headers installed on the system, and that's
exactly the case.

> I am looking at writing a patch for it and send it to xen-devel.
> 
Cool, thanks! I'll be happy to test it. :-)

Regards
-- 
Dario Faggioli, Ph.D
http://about.me/dario.faggioli
Virtualization Software Engineer
SUSE Labs, SUSE https://www.suse.com/
-------------------------------------------------------------------
<<This happens because _I_ choose it to happen!>> (Raistlin Majere)


[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

Re: [Xen-devel] Tools build failure with gcc-9.2.1

[Julien Grall]

Hi Dario,

On 30/03/2020 11:58, Dario Faggioli wrote:
> On Sun, 2020-03-29 at 18:19 +0100, Julien Grall wrote:
>> On 25/03/2020 09:40, Dario Faggioli wrote:
>>> /usr/include/string.h:43:14: note: expected 'void * restrict' but
>>> argument is of type 'const char *'
>>>      43 | extern void *memcpy (void *__restrict __dest, const void
>>> *__restrict __src,
>>>         |              ^~~~~~
>>>
>>> When building with:
>>>
>>> gcc version 9.2.1 20200306 [revision
>>> c5edde44f5b17b4891f17a63517f355bbf89e7d3] (SUSE Linux)
>>>
>>> Already known and being dealt with?
>>
>> I suspect you have a new version of Ocaml built with -safe-string as
>> per
>> [1], String_Val() will return (const char *) rather than (char *).
>>
> Yep, I checked in the ocaml headers installed on the system, and that's
> exactly the case.
> 
>> I am looking at writing a patch for it and send it to xen-devel.
>>
> Cool, thanks! I'll be happy to test it. :-)

I have just posted the patches [1]. This was compiled with OCaml 4.10.x 
and -safe-string. Let me know if it fixes everything on your side.

Cheers,

[1] <20200330192157.1335-1-julien@xen.org>

-- 
Julien Grall