On Mon, Sep 7, 2015 at 9:02 AM, Donald Stufft <donald@stufft.io> wrote:
> On September 3, 2015 at 1:23:03 PM, Nate Coraor (nate@bx.psu.edu) wrote:
>> >>>
>> >>> I'll create PRs for this against wheel and pip shortly. I can also work
>> >>> on a PEP for the platform tag - I don't think it's going to need to be a
>> >>> big one. Are there any preferences as to whether this should be a new PEP
>> >>> or an update to 425?
>> >>>
>
> Coming back to this, I'm wondering if we should include the libc
> implementation/version in a less generic, but still generic linux wheel. Right
> now if you staticly link I think the only platform ABIs you need to worry about
> are libc and Python itself. Python itself is handled already but libc is not.
> The only thing I've seen so far is "build on an old enough version of glibc
> that it handles anything sane", but not all versions of Linux even use glibc at
> all.

This feels kinda half-baked to me?

"linux" is a useful tag because it has a clear meaning: "there exists
a linux system somewhere that can run this, but no guarantees about
which one, good luck". When building a wheel it's easy to tell whether
this tag can be correctly applied.

Distro-specific tags are useful because they also have a fairly clear
meaning: "here's a specific class of systems that can run this, so
long as you install enough packages to fulfill the external
dependencies". Again, when building a wheel it's pretty easy to tell
whether this tag can be correctly applied. (Of course someone could
screw this up, e.g. by building on a system is technically distro X
but has some incompatible hand-compiled libraries installed, but 99%
of the time we can guess correctly.)

If we define a LSB-style base system and give it a tag, like I don't
know, the "Python base environment", call it "linux_pybe1_core" or
something, that describes what libraries are and aren't available and
their ABIs, and provide docs/tooling to help people explicitly create
such wheels and check whether they're compatible with their system,
then this is also useful -- we have proof that this is sufficient to
actually distribute arbitrary software usefully, given that multiple
distributors have converged on this strategy. (I've been talking to
some people off-list about maybe actually putting together a proposal
like this...)

To me "linux_glibc_2.18" falls between the cracks though. If this
starts being what you get by default when you build a wheel, then
people will use it for wheels that are *not* statically linked, and
what that tag will mean is "there exists some system that can run
this, and that has glibc 2.18 on it, and also some other unspecified
stuff, good luck". Which is pretty useless -- we might as well just
stick with "linux" in this case. OTOH if it's something that builders
have to opt into, then we could document that it's only to be used for
wheels that are statically linked except for glibc, and make it mean
"*any* system which has glibc 2.18 or later on it can run this". Which
would be useful in some cases.

But at this point it's basically a
version of the "defined base environment" approach, and once you've
gone that far you might as well take advantage of the various
distributors' experience about what should actually be in that
environment -- glibc isn't enough.

-n

--
Nathaniel J. Smith -- http://vorpus.org