Re: [dpdk-dev] [PATCH] add ABI checks

[Neil Horman <nhorman@tuxdriver.com>]

On Thu, Jan 16, 2020 at 03:20:48PM +0100, Thomas Monjalon wrote:
> 16/01/2020 12:52, Neil Horman:
> > On Wed, Jan 15, 2020 at 01:38:17PM +0100, Thomas Monjalon wrote:
> > > 15/01/2020 12:33, Neil Horman:
> > > > On Wed, Jan 15, 2020 at 12:19:30AM +0100, Thomas Monjalon wrote:
> > > > > 20/12/2019 17:20, Kinsella, Ray:
> > > > > > From: Richardson, Bruce <bruce.richardson@intel.com>
> > > > > > > From: David Marchand <david.marchand@redhat.com>
> > > > > > > > +Checking ABI compatibility
> > > > > > > > +--------------------------
> > > > > > > > +
> > > > > > > > +The first thing is to build reference binaries for the latest
> > > > > > > release
> > > > > > > > +your patches are built on top of.
> > > > > > > > +
> > > > > > > > +Either you are in a git tree and an easy way to identify this is to
> > > > > > > run::
> > > > > > > > +
> > > > > > > > +  git checkout $(git describe --abbrev=0)
> > > > > > > > +
> > > > > > > > +Or you use a tarball and you extract the sources in a director of
> > > > > > > > +your
> > > > > > > > choice.
> > > > > > > > +
> > > > > > > > +Next is building those sources, refer to the previous paragraph.
> > > > > > > > +You can set ``DPDK_BUILD_TEST_DIR=reference``, so that the builds
> > > > > > > > +occur in this directory.
> > > > > > > > +
> > > > > > > > +Finally, the ABI dump files are generated with the
> > > > > > > > +``devtools/gen-abi-reference.sh`` script. This script will look for
> > > > > > > > +builds in the current sub directory ``reference``. But you can set
> > > > > > > > +the environment variable ``DPDK_ABI_REF_BUILD_DIR`` to a different
> > > > > > > location.
> > > > > > > > +
> > > > > > > > +Once done, you can check your current binaries ABI with this
> > > > > > > > +reference with the ``devtools/check-abi-reference.sh`` script.
> > > > > > > >
> > > > > > > 
> > > > > > > I still very much dislike forcing the user to generate his own
> > > > > > > reference version to compare the ABI against. These should be archived
> > > > > > > and the user should just be able to pull them down via git or http or
> > > > > > > otherwise. Two reasons for this:
> > > > > > > 
> > > > > > > 1. Less error prone, since there is no chance of the user having an
> > > > > > > incorrect build for whatever reason.
> > > > > > > 
> > > > > > > 2. Less effort for the user than asking them to do extra builds. The
> > > > > > > more steps the user has to follow, the less likely they are to attempt
> > > > > > > the process.
> > > > > > 
> > > > > > +1 ... 100% agree with this.
> > > > > > 
> > > > > > Many people won't know or understand what the reference is, 
> > > > > > or why they to generate it.
> > > > > 
> > > > > I don't want to generate and save the reference in git for each arch.
> > > > > 
> > > > Can I ask what your reluctance is?  Is it related to not wanting to have to save
> > > > all this information that is otherwise not used for building purposes?
> > > 
> > > Yes I prefer keeping only the sources in the repository.
> > > And these dumps are big.
> > > And last but not the least, there is no ready-to-use environment to build
> > > and dump all libs for all archs.
> > > 
> > > > If so I might suggest saving the dumps in a separate git tree and pulling them
> > > > in as a git submodule when the check is performed
> > > > 
> > > > I really like the idea of caching the results so everyone is working from a
> > > > known ABI baseline.
> > > 
> > > You don't trust the result of the build made from tagged sources?
> > > 
> > I trust the result from the tools, sure, its trusting that people will take the
> > extra time to build a version from a prior tag that I'm less sure of.
> > Consistent use in my mind is predicated on ease and timeliness of use.
> > 
> > I get not wanting to store large dumps in the source tree, but storage is cheap,
> > and I don't see the issue with storing the xml dump in a separate git tree to be
> > referenced through a git submodule that gets pulled in when the check is run.
> 
> Yes this is an option.
> My fear is that this reference database will not be complete
> if we don't build it for all libraries/drivers on all archs,
> managing setups and dependencies.
> 
I can understand that, but I would have assumed that we would have done all
config build for all supported arches as part of the CI for a release, from
which we could archive the results. Is that not the case?

Neil

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