Re: [dpdk-dev] [PATCH v2] abi: change references to abi 20.0.1 to abi v21

[Ray Kinsella <mdr@ashroe.eu>]

On 29/04/2020 13:19, Dodji Seketeli wrote:
> Hello,
> 
> Ray Kinsella <mdr@ashroe.eu> writes:
> 
>> ah ok, the particular system I made the change on was Ubuntu 18.04.2.
>> which is libabigail 1.2.0.
> 
> Whoah, 1.2 is super old.

I have a huge clunking raid'ed "build" server,
that I am pretty conservative about upgrading on v18.04.2 :-)

> In my opinion, one of the hallmarks of static analysis tools (and
> libabigail is just a static analysis framework) is to be able to
> recognize patterns used by developers, as much as we can.
> 
> Because we can't really do that at once, we try to add recognition of
> new patterns (of ABI changes) at every single release.  Furthermore,
> there are some change patterns that ought to be recognized and
> categorized as harmless, whereas some others out to be categorized as
> harmful.  That categorization is also the result of input coming from
> users as you, fine fellows.
> 
> All this to say that with every new version, the number of new supported
> features and bug fixes is potentially big.
> 
> To alleviate that, some distributors update libabigail even in their old
> stable distros, because the value of having an up to date version there
> outweighs the potential drawbacks.

Well it falls into the same category of problems of upgrading compilers.
User's typically build their software build reliably on a given distro version.
(or number of versions). 

If the maintainer upgrades compilers between distro versions, it introduces new 
warnings and errors, and all hell will generally break loose, when the user least expects it. 
They typically expect that mayhem when upgrading to new distro versions. 
Even tools like GNU indent can cause enormous problems. 

I would imagine that most maintainers would be pretty conservative about making
such changes. 

> 
>> Given we still support v19.11 on Ubuntu 18.04.2.
> 
> So maybe that's a discussion worth having with the maintainer of the
> Ubuntu package of Libabigail?

yes - I think it would be an interesting discussion alright.
I imagine the response might be inline with my understanding above.
Let's find out - as we can expect v18.04 to be around for at least another
two years I guess.

Another common way to handle this, is to be really explicit about what 
OS distros DPDK formally supports building on, which will then imply 
we support a small handful of versions of libabigail. 

We then simply say we don't support 18.04 anymore - FD.io VPP are planning 
this formal switch at the moment. 

> 
>> I think it's worthwhile keeping the suppression until v20.11?
> 
> [...]
> 
> David Marchand <david.marchand@redhat.com> writes:
> 
>> In Travis, we currently use libabigail 1.6 (mainly because I did not
>> update to 1.7 when it was released).
> 
> Right, that's probably another way to stay up to date independently from
> the underlying distribution.

You typically don't want to encourage this, you end up with some people
on a newer version, some people on an old version and never upgrading. 

Then you never end up with a consistent view of what mitigations are actually required.
Solving issues, becomes like a game of whack-a-mole. 

> 
> I hope this helps,

It does, greatly thanks. 

> 
> Cheers,
>