Re: [dpdk-dev] [PATCH v1] devtools: update abi ignore for cryptodev

["Kinsella, Ray" <mdr@ashroe.eu>]

On 22/01/2021 13:09, Dodji Seketeli wrote:
> Thomas Monjalon <thomas@monjalon.net> writes:
> 
> [...]
> 
>>>> Then I've added (quickly) a libabigail exception rule:
>>>>
>>>> [suppress_type]
>>>> 	name = rte_cryptodev
>>>> 	has_data_member_inserted_between = {0, 1023}
>>>>
>>>> Now we want to improve this rule to restrict the offsets
>>>> to the padding at the end of the struct only,
>>>> so we keep forbidding changes in existing fields,
>>>> and forbidding additions further the current struct size.
>>>> Is this new rule good?
>>>>
>>>> 	has_data_member_inserted_between = {offset_after(attached), end}
>>>
>>>
>>> Yes, this rule should do what you think it says.
>>>
>>>> Do you confirm that the keyword "end" means the old reference size?
>>>
>>> Yes I do.
>>>
>>>
>>>> What else do we need to check for adding a new field in a padding?
>>>
>>> Actually, that rule will work independantly of it there is enough
>>> padding or not.  It'll shut down the change report, even if the added
>>> data exceeds the padding.
>>
>> I don't understand why.
>> If "end" means the old reference size, then addition after the old size
>> should be reported, isn't it?
> 
> Yes, you are right.
> 
> What I meant is that even if (in an hypothetical case, not yours) the
> padding was so "small" that it wasn't going up to the 'end' of the
> struct, that rule would have still shut down the change report.

Understood - you are talking about padding between members. 

> 
> [...]
> 
> Cheers,
>