Re: [Qemu-devel] [PATCH] build: disable -Wmissing-braces on older compilers

[Paolo Bonzini]

On 20/10/2017 17:08, Laszlo Ersek wrote:
> On 10/20/17 13:02, Paolo Bonzini wrote:
>> On 20/10/2017 12:48, Peter Maydell wrote:
>>> On 20 October 2017 at 11:12, Paolo Bonzini <address@hidden> wrote:
>>>> GCC 4.9 and newer stopped warning for missing braces around the
>>>> "universal" C zero initializer {0}.  One such initializer sneaked
>>>> into scsi/qemu-pr-helper.c and is breaking the build with such
>>>> older GCC versions.
>>>>
>>>> Detect the lack of support for the idiom, and disable the warning
>>>> in that case.
>>>>
>>>> Signed-off-by: Paolo Bonzini <address@hidden>
>>>
>>> AFAIK "{}" will work and not be warned about anywhere (we
>>> use it extensively already) so you don't need to fall back to
>>> memset...
>>
>> Doh, of course that will work in scsi/qemu-pr-helper.c.  In general you
>> can use {0} but not {} to initialize a scalar, like
>>
>>      IDontKnowIfItsAnArrayOrPointer x = {};  //might fail
>>      IDontKnowIfItsAnArrayOrPointer x = {0}; //always works
>>
>> I'm not sure if that matters.
> 
> My remark below might matter even less, but:
> 
> I'd find it regrettable if we suppressed a wrong gcc warning about a
> valid C construct by replacing the construct with a GNU-ism that is
> *not* standard C. :/

Is {} to initialize structs a GNUism?  (Initializing a scalar with {} is
a hard error with GCC).

Paolo