The problem with
Something that crystallized in the process of writing the earlier
Bourne shell quoting entry is that
leads to bad results for the same fundamental reason that multiple
levels of escaping are bad: after a certain point, people can no longer
clearly see what the real code will look like.
When you can't see what the code looks like, it's really hard to make sensible changes; either you make blind stabs or you have to carefully reconstruct the actual code, usually by hand. Either process is error prone, and it's easy to fool yourself, and you are effectively doing remote control programming (with mushy feedback).
Ironically I suspect that the really dangerous
#ifdef'd code is not
the code that is completely snarled up, but the code that is halfway
there. Code that is a complete mess is clearly beyond understanding,
but code that is only half-overgrown with
#ifdefs tempts you into
thinking that you can follow it when you actually can't.
#ifdef'd code that I've personally encountered and
haven't frantically scrubbed out of my brain is the
which is a shining example of what not to do to make a portable