#if foo vs #if defined(foo)

[Guido van Rossum]

In article <1063 at watmath.UUCP> rbutterworth at watmath.UUCP writes:
>A CPP which silently takes undefined symbols to be 0 can be quite
>dangerous.  [lengthy example deleted]

While I agree with your reasoning (the example was quite amazing!), the
ANSI C standard declares that undefined identifiers must be made 0.
Probably too many people have used this feature so they can't break that
existing code :-(

Guido van Rossum, CWI, Amsterdam <guido at mcvax.uucp>