Re: Debian randconfig failure, Was Re: [XEN PATCH v2 0/7] automation: Update containers to allow HTTPS access to xenbits

[Jan Beulich <jbeulich@xxxxxxxx>]

On 21.02.2023 19:05, Andrew Cooper wrote:
> On 21/02/2023 4:55 pm, Anthony PERARD wrote:
>> Building randconfig on debian unstable seems to be an issue.
> 
> You're talking about
> https://gitlab.com/xen-project/people/anthonyper/xen/-/jobs/3769926509 ?
> 
> + gcc --version
> gcc (Debian 12.2.0-14) 12.2.0
> 
> arch/x86/extable.c: In function 'search_pre_exception_table':
> arch/x86/extable.c:200:27: error: array subscript -1 is outside array
> bounds of 'struct exception_table_entry[1152921504606846975]'
> [-Werror=array-bounds]
>   200 |     unsigned long fixup = search_one_extable(
>       |                           ^~~~~~~~~~~~~~~~~~~
>   201 |         __start___pre_ex_table, __stop___pre_ex_table-1, addr);
>       |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> In file included from arch/x86/extable.c:8:
> ./arch/x86/include/asm/uaccess.h:414:37: note: at offset -8 into object
> '__stop___pre_ex_table' of size [0, 9223372036854775807]
>   414 | extern struct exception_table_entry __stop___pre_ex_table[];
>       |                                     ^~~~~~~~~~~~~~~~~~~~~
> cc1: all warnings being treated as errors
> make[3]: *** [Rules.mk:246: arch/x86/extable.o] Error 1
> 
> Jan: do we need some more gcc-wrap sprinkled around?

I think we can get away without, but first of all I'm curious why gcc12
spots an issue there, but not in my (and perhaps also your) local builds.
Being a randconfig failure, is this tied to a specific setting in .config?
Off the top of my head I can't think of any which might affect this code.

To work around this, instead of adding gcc-wrap-ery, I'd favor simply
changing search_one_extable()'s 2nd parameter's meaning from "last" to
"end" (i.e. the range passed in from [,] to [,) in mathematical spelling).

Jan