[llvm-dev] [lldb-dev] [cfe-dev] What version comes after 3.9? (Was: [3.9 Release] Release plan and call for testers)

Robinson, Paul via llvm-dev llvm-dev at lists.llvm.org
Tue Jun 28 10:03:50 PDT 2016

> -----Original Message-----
> From: hwennborg at google.com [mailto:hwennborg at google.com] On Behalf Of Hans
> Wennborg
> On Mon, Jun 27, 2016 at 7:57 PM, Chris Lattner <clattner at apple.com> wrote:
> > I still don’t understand what “confusion” could be caused by going from
> 3.9 to 4.0.  Could someone please elaborate on what the problem is that
> needs solving?  If it is that people don’t understand what is major about
> the release, I would say “who cares”?
> I think the main issue (besides users asking what's the big change in
> 4.0, which I agree is not a big problem) is that the bitcode
> compatibility policy is tied to the major version number.

Somebody proposed a time-based-version bitcode compatibility policy.
IMHO the easiest to remember would be "X.Y supports back to (X-1).Y"
but opinions vary (e.g. 3 years, where my idea would mean 5 years) and
nobody has tried to nail one down.

Of course actually removing an auto-upgrade feature means having to do
the archaeology to figure out when each piece was introduced, and then
how to disentangle it cleanly.  I'm not aware that these things are
identified by version, other than by researching the commit history.
With the old scheme, you'd just rip it all out at 4.1 without having
to worry about when each piece was introduced.  With the time-based
scheme there's a higher barrier to removing the old code.

> But if you really insist on 4.0 rather than 3.10, I will of course honour
> that.
> Cheers,
> Hans

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