Re: abidiff improvements for kernel UAPI checker

[Trilok Soni <quic_tsoni@quicinc.com>]

On 4/10/2023 5:45 PM, John Moon wrote:
> Hi all,
> 
> As you may be aware from the Linux kernel mailing list threads I've been 
> CC'ing you on, we're in the process of upstreaming a shell script that 
> uses abidiff to compare Linux kernel userspace APIs between revisions. 
> Linux UAPIs are supposed to be stable forever, so we're trying to detect 
> when a patch breaks a UAPI.
> 
> If you haven't been following, the latest thread is here: 
> https://lore.kernel.org/lkml/20230407203456.27141-1-quic_johmoo@quicinc.com/
> 
> At a high level, we're taking the header file before/after the patch, 
> building it in a dummy C file, then taking advantage of abidiff's 
> "--non-reachable-types" argument to compare all the symbols.
> 
> This method works great! However, there are a couple of classes of ABI 
> differences that are detected but don't qualify as UAPI-breaking.
> 
> By far the most common class of differences occur with enum expansions.
> 
> For example, this change triggers finding: 
> https://github.com/torvalds/linux/commit/622f1b2fae2eea28a80b04f130e3bb54227699f8#diff-a7f82b68b3459e13934c123bda4c3a9be20eadebe938a376e39a395e5ffa825a

Any inputs here from the libabigail mailing list here?

---Trilok Soni