Re: [PATCH 3/4] pc-bios/s390-ccw: Silence GCC 11 stringop-overflow warning

[Philippe Mathieu-Daudé]

On 5/3/21 11:00 AM, Cornelia Huck wrote:
> On Sun,  2 May 2021 19:48:35 +0200
> Thomas Huth <thuth@redhat.com> wrote:
> 
>> From: Philippe Mathieu-Daudé <philmd@redhat.com>
>>
>> When building on Fedora 34 (gcc version 11.0.0 20210210) we get:
>>
>>   In file included from pc-bios/s390-ccw/main.c:11:
>>   In function ‘memset’,
>>       inlined from ‘boot_setup’ at pc-bios/s390-ccw/main.c:185:5,
>>       inlined from ‘main’ at pc-bios/s390-ccw/main.c:288:5:
>>   pc-bios/s390-ccw/libc.h:28:14: warning: writing 1 byte into a region of 
>> size 0 [-Wstringop-overflow=]
>>      28 |         p[i] = c;
>>         |         ~~~~~^~~
>>
>> The offending code is:
>>
>>   memset((char *)S390EP, 0, 6);
>>
>> where S390EP is a const address:
>>
>>   #define S390EP 0x10008
>>
>> The compiler doesn't now how big that pointed area is, so assume its
> 
> s/now/know/
> s/assume/it assumes that/

Oops, thanks. Thomas, do you want me to repost this patch fixed?

>> length is zero. This has been reported as BZ#99578 to GCC:
>> "gcc-11 -Warray-bounds or -Wstringop-overread warning when accessing a
>> pointer from integer literal"
>> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99578
>>
>> As this warning does us more harm than good in the BIOS code (where
>> lot of direct accesses to low memory are done), silence this warning
>> for all BIOS objects.
>>
>> Suggested-by: Thomas Huth <thuth@redhat.com>
>> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>> Message-Id: <20210422145911.2513980-1-philmd@redhat.com>
>> Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
>> [thuth: Use the pre-existing cc-option macro instead of adding a new one]
>> Signed-off-by: Thomas Huth <thuth@redhat.com>
>> ---
>>  pc-bios/s390-ccw/Makefile | 1 +
>>  1 file changed, 1 insertion(+)