[PATCH] assert: Suppress pedantic warning caused by statement expression [BZ# 21242]

[Florian Weimer]

On 07/05/2017 10:15 PM, Zack Weinberg wrote:
> On Wed, Jul 5, 2017 at 11:51 AM, Florian Weimer <fweimer@redhat.com> wrote:
>> On 07/05/2017 05:46 PM, Zack Weinberg wrote:
>>> A problem occurs to me: expressions involving VLAs _are_ evaluated
>>> inside sizeof.
>>
>> The type of the sizeof argument would still be int (due to the
>> comparison against 0), so this doesn't actually occur.
> 
> I rechecked what C99 says about sizeof and VLAs, and you're right -
> the operand of sizeof is only evaluated when sizeof is _directly_
> applied to a VLA.  So this is indeed safe, but I think this wrinkle
> should be mentioned in the comment.  Perhaps
> 
> /* The first occurrence of EXPR is not evaluated due to the sizeof,
>    but will trigger any pedantic warnings masked by the __extension__
>    for the second occurrence.  The explicit comparison against zero
>    ensures that sizeof is not directly applied to a function pointer or
>    bit-field (which would be ill-formed) or VLA (which would be evaluated).  */
> 
> zw

What about the attached patch?

Siddhesh, is this okay during the freeze?  I'd like to backport it to
2.25 as well.

Thanks,
Florian
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