> On Feb 1, 2023, at 1:57 PM, Siddhesh Poyarekar <siddh...@gotplt.org> wrote:
>
> On 2023-02-01 13:24, Qing Zhao wrote:
>>> On Feb 1, 2023, at 11:55 AM, Siddhesh Poyarekar <siddh...@gotplt.org> wrote:
>>>
>>> On 2023-01-31 09:11, Qing Zhao wrote:
>>>> Update documentation to clarify a GCC extension on structure with
>>>> flexible array member being nested in another structure.
>>>> gcc/ChangeLog:
>>>> * doc/extend.texi: Document GCC extension on a structure containing
>>>> a flexible array member to be a member of another structure.
>>>
>>> Should this resolve pr#77650 since the proposed action there appears to be
>>> to document these semantics?
>> My understanding of pr77650 is specifically for documentation on the
>> following case:
>> The structure with a flexible array member is the middle field of another
>> structure.
>> Which I added in the documentation as the 2nd situation.
>> However, I am still not very comfortable on my current clarification on this
>> situation: how should we document on
>> the expected gcc behavior to handle such situation?
>
> I reckon wording that dissuades programmers from using this might be
> appropriate, i.e. don't rely on this and if you already have such nested flex
> arrays, change code to remove them.
Good suggestion.
>
>>>> +In the above, @code{flex_data.data[]} is allowed to be extended flexibly
>>>> to
>>>> +the padding. E.g, up to 4 elements.
>
> """
> ... Relying on space in struct padding is bad programming practice and any
> code relying on this behaviour should be modified to ensure that flexible
> array members only end up at the ends of arrays. The `-pedantic` flag should
> help identify such uses.
> """
>
> Although -pedantic will also flag on flex arrays nested in structs even if
> they're at the end of the parent struct, so my suggestion on the warning is
> not really perfect.
Yes, both the situations (flex arrays nested in the end of of structures, or
flex array nested in the middle of structures) are NOT standard-conforming, we
might need to dis-encourage both situations?
Qing
>
> Sid
