Re: [gentoo-dev] Re: [PATCH/RFC] eclass/flag-o-matic.eclass: prepend-ldpath

[Marien Zwart]

On Monday 15 October 2012 04:35:09 Gregory M. Turner wrote:
> On 10/14/2012 9:29 PM, Mike Frysinger wrote:
> > Python clearly has an amazing community, so I hate to say anything
> > negative... but I sometimes wish they would "build" less and "buy" more.
>
> build systems are hard to get right.  python is in the situation where the
> setups they care about mostly work and people generally aren't complaining,
> but it's more through a hack effort than doing it right which means all the
> other cases they haven't considered break horribly.  cross-compiling for
> example has never worked correctly out of the box.

The reasons for Python's awkward build system are probably mostly
historical. I'll (unsuccessfully) try to keep this brief, but still:

Python is old: Python 1.0.0 was released January 1994, and Python
existed before that. I don't know what its build system was like back
then, but most systems you might want them to "buy" didn't exist yet.

Distutils (the build system for external extension modules as well as
chunks of Python's standard library) is still old: it was integrated
into Python 1.6 (September 5, 2000). Autoconf 2.13 existed, 2.50
wasn't there yet. Looks like CMake was just turned into a separate
project around that time.

Python's needs are a little special: you can build extension modules
using just Python and a C compiler (and you don't need the C compiler
if your code is pure-python). This is important on awkward platforms
(currently mostly Windows, but I'm pretty sure there were others
similarly awkward). This same Python-powered build system is used to
build part of the standard library, for obvious reasons. And there are
other build systems that make use of python mainly to be
cross-platform (scons and derivatives mostly).

It would probably be possible to redo Python's own build system now
and end up with something better, but I'm not aware of anyone having
seriously attempted this, probably because it's just not quite broken
enough to be worth it. The awkwardness of distutils we're somewhat
stuck with, although there are efforts to modernize and clean up
distutils. I'm not so sure there's anything they could have "bought"
to replace Python's own build system, let alone distutils (build
systems like automake actually use distutils.sysconfig), without a
working time machine (and a rather confusing time loop to allow build
systems that currently support python to do so without
distutils.sysconfig).

-- 
marienz.