Bug#729924: vim: Add Python 3 support

[James McCoy]

On Mon, Nov 18, 2013 at 05:59:02PM -0500, Barry Warsaw wrote:
> I'm not a vim user but I'm am very interested in porting the world to
> Python 3.  To that end, I see that the current version of upstream vim
> supports Python 3, but building that is not currently enabled in the
> Debian package.

This is due to two things.

First, the way Debian builds Python prevents loading both libpython2 and
libpython3 in the same process, since Debian's builds necessitate
passing RTLD_GLOBAL to dlopen().  This means that when Vim is built to
support both Python 2 & 3, one has to choose between using plugins that
target Python 2 or Python 3 instead of the user being able to use both.

At the time, this meant I had to choose one and I went with Python 2 due
to the much higher prevalence of plugins targeting it.  While Python 3
has gained a lot of ground since then and it's much more easy to write
code that works in both versions, my understanding is that the
RTLD_GLOBAL issue still exists.  This means I still need to choose one
version and, while it's more of a toss up now, I think Python 2 is still
the right call here.

Second, I'm not keen on the state of dependency tracking with software
that dynamically loads libraries instead of linking against them.  If
Vim dynamically loaded its own code that provides the language bindings,
and those were linked against the proper language libraries, then I
could easily provide vim-{lua,perl,python,ruby,tcl}-bindings packages
which expressed proper relationships on the corresponding language
libraries.

Since that isn't the case, we can then run into situations where bad
things happen during a library transition due to nothing telling the
transition trackers that Vim should actually be rebuilt or forcing the
users to upgrade Vim in sync with the library.  See #611573 for some
previous discussion about this related to Vim's Perl support.

Cheers,
-- 
James
GPG Key: 4096R/331BA3DB 2011-12-05 James McCoy <jamessan at debian.org>
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