Re: [PATCH] RFC: Version support policy

[Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>]

On Fri, Aug 13, 2021 at 12:37:27PM +0100, Ian Jackson wrote:
> The current policy for minimum supported versions of tools, compilers,
> etc. is unsatisfactory: For many dependencies no minimum version is
> specified.  For those where a version is stated, updating it is a
> decision that has to be explicitly taken for that tool.
> 
> The result is persistent debates over what is good to support,
> conducted in detail in the context of individual patches.
> 
> Decisions about support involve tradeoffs, often tradeoffs between the
> interests of different people.  Currently we don't have anything
> resembling a guideline.  The result is that the individual debates are
> inconclusive; and also, this framework does not lead to good feelings
> amongst participants.
> 
> I suggest instead that we adopt a date-based policy: we define a
> maximum *age* of dependencies that we will support.

I wonder about another approach: specify supported toolchain version(s)
based on environments we choose to care about. That would be things like
"Debian, including LTS (or even ELTS) one", "RHEL/CentOS until X...",
etc. Based on this, it's easy to derive what's the oldest version that
needs to be supported.
This would be also much friendlier for testing - a clear definition
what environments should be used (in gitlab-ci, I guess).

Thoughts?

> The existing documentation about actually known working versions
> then becomes a practical consequence of that policy.
> 
> In this patch I propose a cutoff of 6 years.
> Obviously there will be debate about the precise value.
> 
> It will also be necessary to make exceptions, and/or to make different
> rules for different architectures.  In particular, new architectures,
> new configurations, or new features, may need an absolute earliest
> tooling date which is considerably less than the usual limit.
> 
> I have tried to transcribe the current compiler version info into this
> format.  The dates in the exceptions are all more recent than my
> suggested 6 year cutoff, so if this patch is applied to staging and
> not applied retrospectively, they could be removed.
> 
> I'm not sure if this policy should be here in README (where the
> version support was until now) or in SUPPORT.md.

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab

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