[Python-3000] AtheOS?

[Stephen J. Turnbull]

Alexandre Vassalotti writes:

 > Perhaps, it would be a good idea to take Plan9's approach to
 > portability -- i.e., you develop an extreme allergy to code filled
 > with #if, #ifdef, #else, #elseif; localize system dependencies in
 > separate files and hide them behind interfaces.

If I understand correctly, Emacs uses this approach (although not
thoroughly).  The resulting portability files are called s & m files
for several reasons.  One of course is that they are kept in
subdirectories called "s" for "system" and "m" for "machine".  The
more relevant here is the pain they inflict on developers, because
they make it more difficult to find implementations of functions, and
hide (or at least distribute across many files) potentially relevant
information.

Although parsing a deep #ifdef tree is very error-prone and annoying,
this can be improved with technology (eg, hideif.el in Emacs).  The
#ifdef approach also has an advantage that all alternative
implementations and their comments are in your face.  Mostly they're
irrelevant, but often enough they're very suggestive.  Though I
suppose a sufficiently disciplined programmer would think to use that
resource if split out into files, I am not one.  This is an important
difference between the approaches for me and perhaps for others who
only intermittently work on the code, and only on parts relevant to
their daily lives.

In the end, the difference doesn't seem to be that great, but for us
preferred practice (especially as we add support for new platforms) is
definitely to put the platform dependencies into configure, to try to
organize them by feature rather than by cpu-os-versions-thereof, and
to use #ifdefs.

FWIW YMMV.