A reply to Ned from the person who introduced this bug in the first
place (sorry, folks):

[Ned]
> 1. How to make core developers and patch contributors more aware of the 
> special requirements of multi-architecture builds?

I guess I was already aware of this, at least after Ned (IIRC), some
months ago, detected essentially the same problem in py3k after we'd put
the short float repr in.  So this was really just sloppiness on my part.
 I did testing of the short float repr for single-architecture builds on
OS X 10.4/PPC (32-bit), OS X 10.5/Intel (32-bit and 64-bit) and OS X
10.6/Intel (64-bit only), but still missed this.

Something that I would have found helpful at one stage would be
prominent instructions (somewhere, maybe in the python-dev FAQ?) for
creating and testing multi-architecture builds on various OS X versions.
 Perhaps all those instructions need to do is to point to the
Mac/BuildScript/README.txt?  Even now, I'm still not 100% clear on
exactly which selection of options should be supplied to the configure
scripts, and why.

> At a minimum, I would like to see a message added to configure.in that 
> is output on OS X to warn that some of the autoconf derived values for 
> architecture-specific SIZEOF and processor features are overridden in 
> Include/pyconfig.h.

Do you mean Include/pymacconfig.h?  If so, I agree such a warning would
be good to have.

As an aside, I *think* it's actually safe just to undefine
HAVE_GCC_ASM_FOR_X87 unconditionally on OS X:  the inline assembler that
it enables is only ever used for machines which suffer from double
rounding, which is a symptom of using the x87 FPU for basic arithmetic.
gcc on OS X (either Apple gcc or GNU gcc) always seems to use SSE2
instructions for arithmetic, even for 32-bit builds, so the fnstcw and
fldcw instructions aren't ever needed or used on OS X.