Re: [Qemu-devel] [PATCH] atomic.h: Work around gcc spurious "unused value" warning

[Peter Maydell]

On 10 May 2018 at 15:37, Richard Henderson <address@hidden> wrote:
> On 05/10/2018 07:36 AM, Peter Maydell wrote:
>> Some versions of gcc produce a spurious warning if the result of
>> __atomic_compare_echange_n() is not used and the type involved
>> is a signed 8 bit value:
>>   error: value computed is not used [-Werror=unused-value]
>> This has been seen on at least
>>  gcc (Ubuntu 5.4.0-6ubuntu1~16.04.9) 5.4.0 20160609
>>
>> Work around this by using an explicit cast to void to indicate
>> that we don't care about the return value.
>>
>> We don't currently use our atomic_cmpxchg() macro on any signed
>> 8 bit types, but the upcoming support for the Arm v8.1-Atomics
>> will require it.
>>
>> Signed-off-by: Peter Maydell <address@hidden>
>> ---
>> Sending out my workaround as an actual patch. If this is OK I'll
>> put in via target-arm.next as it's a dependency for the v8.1-atomics
>> series.
>>
>>  include/qemu/atomic.h | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> Reviewed-by: Richard Henderson <address@hidden>

Thanks. Do we care about trying to follow up on the gcc side
to find out if this is a definitely-fixed bug?

-- PMM