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

[Julien Grall <julien@xxxxxxx>]

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