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 22.02.2023 10:42, Jan Beulich wrote:
> 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.

Looks to be the combination of DEBUG=n and COVERAGE=y.

> 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).

I'll make a patch along these lines then, I guess. Should I credit Anthony,
you, or both of you as the reporter?

Jan