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

[Laszlo Ersek <lersek@redhat.com>]

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 <pbonzini@redhat.com> 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 <pbonzini@redhat.com>
>>
>> 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. :/

Laszlo