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Subject: Re: [PATCH v5 1/2] check-uapi: Introduce check-uapi.sh
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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From:   John Moon <quic_johmoo@quicinc.com>
In-Reply-To: <2023041209-armed-overlaid-3d3d@gregkh>
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On 4/11/2023 11:14 PM, Greg Kroah-Hartman wrote:
>> Would you find the tool more useful if it simply filtered out all instances
>> where the size of the type did not change? This would filter out the
>> following which the tool currently flags:
>>
>> - enum expansions
>> - reserved field expansions
>> - expansions of a struct with a flex array at the end
>> - type changes
>> - re-ordering of existing members
>> - ...others?
> 
> Obviously not, as some of those are real breakages, and some are not at
> all.
> 
> Please understand what is an abi breakage.  Adding new enums is not.
> Using a reserved field is not.  Reording existing members IS.
> 

Yes, understood that method would miss certain classes of breakages. I 
was suggesting it as a way to improve the signal-to-noise ratio of the 
tool since we don't currently have an algorithm for determining 
breakages with 100% accuracy.

We'll work internally and with the libabigail team to improve the story 
here and get back to you. Thanks for the discussion!

- John