On 11/02/2021 11:53, Jan Beulich wrote: > On 11.02.2021 12:30, Andrew Cooper wrote: >> On 11/02/2021 11:05, Jan Beulich wrote: >>> On 11.02.2021 02:08, Andrew Cooper wrote: >>>> Hello, >>>> >>>> Last things first, some examples: >>>> >>>> http://xenbits.xen.org/people/andrewcoop/abi/libxenevtchn-1.1_to_1.2.html >>>> http://xenbits.xen.org/people/andrewcoop/abi/libxenforeignmemory-1.3_to_1.4.html >>>> >>>> These are an ABI compatibility report between RELEASE-4.14.0 and staging. >>>> >>>> They're performed with abi-dumper (takes a shared object and header >>>> file(s) and write out a text "dump" file which happens to be a perl >>>> hash) and abi-compliance-checker checker, which takes two dumps and >>>> produces the HTML reports linked above. They're both debian tools >>>> originally, but have found their way across the ecosystem. They have no >>>> impact on build time (when invoked correctly). >>>> >>>> I'm encouraged to see that the foreignmem analysis has even spotted that >>>> we deliberately renamed one parameter to clarify its purpose. >>>> >>>> >>>> For the stable libraries, the RELEASE-$X.$Y.0 tag is the formal point >>>> when accumulated changes in staging become fixed. What we ought to be >>>> doing is taking a "dump" of libraries at this point, and publishing >>>> them, probably on xenbits. >>>> >>>> Subsequent builds on all the staging branches should be performing an >>>> ABI check against the appropriate lib version. This will let us catch >>>> breakages in staging (c/s e8af54084586f4) as well as breakages if we >>>> ever need to backport changes to the libs. >>>> >>>> For libraries wrapped by Juergen's tools/libs/ common-makefile changes, >>>> adding ABI dumping is easy. The only complicating is needing to build >>>> everything with "-Og -g", but this is easy to arrange, and frankly ought >>>> to be the default for debug builds anyway (the current use of -O0 is >>>> silly and interferes with common distro hardening settings). >>>> >>>> What I propose is tweaking the library build to write out >>>> lib$FOO.so.$X.$Y-$(ARCH).abi.dump files. A pristine set of these should >>>> be put somewhere on xenbits, and a task put on the release technicians >>>> checklist for future releases. >>>> >>>> That way, subsequent builds which have these tools available can include >>>> a call to abi-compliance-checker between the authoritative copy and the >>>> one from the local build, which will make the report available, and exit >>>> nonzero on breaking problems. >>>> >>>> >>>> To make the pristine set, I need to retrofit the tooling to 4.14 and >>>> ideally 4.13. This is in contravention to our normal policy of not >>>> backporting features, but I think, being optional build-time-only >>>> tooling, it is worthy of an exception considering the gains we get >>>> (specifically - to be able to check for ABI breakages on these branches >>>> in OSSTest). Backporting to 4.12 and older is far more invasive, due to >>>> it being before the library build systems were common'd. >>>> >>>> >>>> Anyway, thoughts? >>> +1 >>> >>> Not sure about the backporting effects - tools/libs/ had quite a bit >>> less content in 4.14 and older, so the coverage would be smaller. >> tools/libs/ has been the stable libraries, since IanC split them years >> ago. The only odd-one-out is libxenstored IIRC, which moved during the >> 4.15 window. > As well as ctrl/, guest/, light/, stat/, util/, and vchan/.
Right, but 5 of those don't have stable ABIs. ~Andrew
