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. ~Andrew
