Messages in this thread | | | Date | Thu, 13 Apr 2023 10:15:24 -0700 | Subject | Re: [PATCH v5 1/2] check-uapi: Introduce check-uapi.sh | From | John Moon <> |
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On 4/13/2023 7:37 AM, Mark Wielaard wrote: > Hi, > > On Wed, 2023-04-12 at 09:37 -0700, John Moon via Libabigail wrote: >> 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. > > Note that you can check the exit code of libabigail's abidiff to see > whether something is an incompatible abi change or not, see: > https://sourceware.org/libabigail/manual/abidiff.html#return-values > > You can also of course use suppressions to instruct abidiff to avoid > reporting changes involving certain ABI artifacts: > https://sourceware.org/libabigail/manual/libabigail-concepts.html#suppr-spec-label > > Cheers, > > Mark
Checking the ABIDIFF_ABI_INCOMPATIBLE_CHANGE flag in the return code is a good idea, but checking it doesn't change what the tool is currently outputting (i.e. the flag is set for all the changes currently reported). I think this is because of some filtering we're doing based on grepping stdout, but checking the return code would be more stable.
The suppressions may work for some cases, but I fear they would be too eager in other cases. Looking at the docs, I'm not sure how we could express something like:
"suppress changed enumerators if they end in 'MAX' or 'LAST' and appear at the end of the enumeration"
or
"suppress data member insertions into a struct if the last member in the struct has its size reduced by sizeof(new_member) and is named 'pad' or 'reserved'"
They're complicated cases to detect in a general way.
Thanks, John
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