[Python-Dev] Status of C compilers for Python on Windows

[Stephen J. Turnbull]

Tony Kelman writes:

 > No, just hearing the words come out of my mouth they sound a little
 > nuts.  Maybe not, there are after all half a dozen or more
 > incompatible alternate Python implementations floating around. I
 > think most of them started as from-scratch rewrites rather than
 > source forks, but maybe that's irrelevant.

Well, they have different names and they clearly are not intended to
be ABI compatible, so noone expects that.  OTOH, there clearly is an
expectation among many (and not just in the Windows world, cf. all of
the distros that provide whole stacks of everything for each version
of Python) that downloaded packages will just work without
incompatibility.

 > > Well, for starters, most of python-dev would rather avoid any contact
 > > whatsoever with Windows.  I think part of the problem is that Windows
 > > developers *of* Python are *very* rare (fingers of one hand rare).
 > 
 > In my opinion the MSVC toolchain makes that problem worse, as it's far
 > harder for unix developers to have any familiarity with how things
 > work.

I've used Cygwin, I've used MinGW, and I've used VC.  Sure, the former
two are GCC-based so I have a lot of muscle memory for command-line
switches.  But that's not very important; the pain of using Windows is
what drives me away from all of them.

 > But you do have involvement and core developers from Microsoft
 > which is obviously incredibly important. Maybe even mandatory for
 > Python on Windows to be viable in your eyes.

No, I don't think that's true.  What I think *is* true is that most
developers on Windows do have access to Microsoft tools, so we do need
to provide compatibility with them.  As you say, the VC toolchain is
not all things to all men, but what's visible to python-dev makes it
more important than Cygwin or MinGW.  See Paul Moore's post about
communications between the scientific Python community and python-dev
for what I mean by "visible".

 > > It should be evident by now that our belief is that the large
 > > majority of Windows users is well-served by the current model
 > 
 > This is not the case at all in the scientific community. NumPy and
 > SciPy put in a lot of extra work to come up with something that is
 > compatible with the MSVC build of CPython because they have to, not
 > because they're "happy to" jump through the necessary hoops.

Agreed.  This is well-known to python-dev, and AFAICS it *is* a
concern for us.  However, as Paul points out, a bridge needs to be
built.  Your posts have been a contribution to building that bridge,
for sure, but more work on the bridge is needed.

 > Do python-dev and numpy-discussion not talk to one another?

Exactly the issue here.  To resolve this, we need to talk more.
Unfortunately, I'm not one to help build the bridge as I haven't
developed on Windows at all since about 2003.

 > I'm going to move the "extensions with MinGW-w64" part of this
 > conversation over to numpy-discussion,

As far as I can tell, that's a good idea right now.  They have the
need, they have the expertise, both of which are somewhat lacking
here.

 > Okay. I'll table the discussion with python-dev for now then.

I hope you'll be able to come pick it back up at some point.  You
might want to interact with Steve Dower off-list, as he's spearheading
the effort to move the official builds to the "stable ABI" version of
MSVC.  Once that's in place, the MinGW guys will have a stationary
target which is up to date to shoot at.