[Distutils] Binary Wheels and "universal" builds on OS-X

[Daniel Holth]

Wheel already supports compound tags. Just like py2.py3-none-any a tag
py3-none-x86.ppc (with real platform names) would work. Does that make
sense for Mac?
On May 31, 2013 6:30 PM, "Chris Barker - NOAA Federal" <
chris.barker at noaa.gov> wrote:

> HI Folks,
>
> A few of us over on the pythonmac list have been hashing out how best
> to support binary packages on OS-X. The binary wheel option seems very
> promising.
>
> However, there is one Mac-specific issue that does not seem to be
> addressed:
>
> On OS-X, binaries can be "universal" -- what this means is that they
> have more than one binary architecture embedded in a single file; the
> system selects the right one at run time. Both executables and dynamic
> libraries can be universal. In theory, an universal binary can
> currently contain up to 4 architectures:
>
> 32+64 bit PPC and 32+64bit x86
>
> In practice, 64 bit PPC was never broadly used, and 32bit PPC is
> fading fast. Nevertheless, both 32 and 64 Intel systems are pretty
> common, and who knows what there may be in the future (you never know
> with Apple...)
>
> The binary builds of Python served up on the python.org web site have
> supported universal builds for years -- currently there are two
> options: 32bit PPC+x86 or 32+64bit x86. It's not a single build, as it
> turns out it's hard to support both up to date x86_64 and PPC with the
> same compiler. In these builds, the configuration is set up so that
> distutils will build universal extensions that match the architectures
> included in the builds. This makes it pretty easy to build binary
> packages, and/or full app distributions (py2app) that are universal as
> well.
>
> setuptools' easy_install supports binary eggs, but always choked on
> universal builds -- it didn't know how to identify what matched the
> system. It would be really nice if future tools could identify and
> install the correct binary wheels for universal builds.
>
> I've taken a look at PEP 427, and see this:
>
> platform tag
> E.g. 'linux_x86_64', 'any'.
>
> That looks to me like there is a built-in assumption that a wheel is
> either specific to a single architecture, or any -- so no way to
> specify that it may have multiple architectures. So I propose that
> platform tag allow a list of some sort:
>
> ['macosx-10_6_i386', 'macosx_10_6-x86_64']
>
> or, I suppose to keep it simple, a single string:
>
> 'macosx_10_6_i386+macosx_10_6_x86_64'
> or
> 'macosx_10_6_i386+x86_64'
>
> If so, then a binary wheel could be built (and discovered) that
> supported multiple architectures.
>
> Then how would an installer ( pip? ) identify the right one? This is a
> bit tricky. PEP 425 states:
>
> "The platform tag is simply distutils.util.get_platform() with all
> hyphens - and periods . replaced with underscore"
>
> On my system right now, I have 32bitPPC + 32bit i386 universal python,
> running on an intel system:
>
> In [2]: distutils.util.get_platform()
> Out[2]: 'macosx-10.3-i386'
>
> So we may want to patch get_platform() to support universal builds -
> or add anther function or something -- you may sometimes what to know
> what you are running right now, and other times want to know how the
> current python is built. (note that while distutils can build
> universal binaries, it's not very smart about it -- all is does is
> grab the compiler and linker flags from the Makefile, which include
> multiple "-arch" flags.
>
> Even if there is an easy way to query the system, that leaves the
> question of what to do. If a user wants to intall a package into a
> universal python, will the installer only accept a binary wheel with
> all the supported architectures? or one with only the currently
> running one?
>
> Anyway, it would be nice to be able to get this stuff to "just work"
> with universal binaries on the Mac.
>
> Thoughts, ideas?
>
> -Chris
>
>
>
> --
>
> Christopher Barker, Ph.D.
> Oceanographer
>
> Emergency Response Division
> NOAA/NOS/OR&R            (206) 526-6959   voice
> 7600 Sand Point Way NE   (206) 526-6329   fax
> Seattle, WA  98115       (206) 526-6317   main reception
>
> Chris.Barker at noaa.gov
> _______________________________________________
> Distutils-SIG maillist  -  Distutils-SIG at python.org
> http://mail.python.org/mailman/listinfo/distutils-sig
>
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