[llvm-dev] LLVM Releases: Upstream vs. Downstream / Distros

[David Chisnall via llvm-dev]

On 12 May 2016, at 16:53, Renato Golin via llvm-dev <llvm-dev at lists.llvm.org> wrote:
> 
> On 12 May 2016 at 16:47, Antoine Pitrou via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
>> +1 to this.  As a developer of llvmlite and numba, it would be
>> counter-productive for me to try to follow the LLVM ToT, as opposed to
>> migrate after a X.Y.1 release as we currently do.
> 
> There's also how many APIs do we create packages for?
> 
> If your projects use 3.5, some others use 3.6, etc. then distros need
> to keep packages for *all* of them and *also* have Clang packages,
> maybe more than one. This can get nasty...
> 
> I'm not sure how to solve that... :(

With my downstream hat on, this isn’t really a problem for FreeBSD in most cases.  We have ports for LLVM 3.3 and upwards (3.2 earlier have no remaining users and have been removed).  Aside from disk space usage, it’s only a problem when we find a program that links to two things that link to different versions of LLVM, which is fairly rare.  We could fix this fairly trivially by sticking everything in headers in an llvm_{major}_{minor} namespace just as libc++ puts everything in a __v1 namespace.

As long as we have only a handful of different releases to support, it’s fine.  The problem only comes when we have a few hundred API-incompatible versions in between X.Y and X.Y+1 (I don’t even care about ABI compatibility with this hat on, as we recompile the entire ports collection every time that we generate a new package set).

David

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