Re: [PATCH v2 2/6] configure: avoid new clang 11+ warnings

[Daniele Buono <dbuono@linux.vnet.ibm.com>]

Hi Paolo,
I reorganized UASStatus to put uas_iu at the end and it works fine.
Unfortunately, this uncovered another part of the code with a similar
issue (variable sized type not at the end of the struct), here:

In file included from ../qemu-cfi-v3/target/s390x/diag.c:21:
../qemu-cfi-v3/hw/s390x/ipl.h:161:23: error: field 'iplb' with variable 
sized type 'IplParameterBlock' (aka 'union IplParameterBlock') not at 
the end of a struct or class is a GNU extension 
[-Werror,-Wgnu-variable-sized-type-not-at-end]
     IplParameterBlock iplb;
                       ^
../qemu-cfi-v3/hw/s390x/ipl.h:162:23: error: field 'iplb_pv' with 
variable sized type 'IplParameterBlock' (aka 'union IplParameterBlock') 
not at the end of a struct or class is a GNU extension 
[-Werror,-Wgnu-variable-sized-type-not-at-end]
     IplParameterBlock iplb_pv;

My understanding is that each of these IplParameterBlock may contain
either a IPLBlockPV or a IplBlockFcp, which both end with a variable
sized field (an array).

Adding maintainers of s390x to see if they have a suggested solution to
avoid disabling the warning.

On 10/26/2020 5:50 AM, Paolo Bonzini wrote:
> On 23/10/20 22:06, Daniele Buono wrote:
>> 1 error generated.
>>
>> The data structure is UASStatus, which must end with a QTAILQ_ENTRY, so
>> I believe we cannot have uas_iu at the end. Since this is a gnu
>> extension but CLANG supports it, just add
>> -Wno-gnu-variable-sized-type-not-at-end
> 
> This is potentially a real bug, in this case it works only because
> UASStatus's packet is never uas_iu_command (which has the variable sized
> type).
> 
> The QTAILQ_ENTRY need not be at the end, please rearrange UASStatus's
> field so that the "usb_ui status" field is the last.
> 
> Thanks,
> 
> Paolo
>