Simple C Puzzle #1 Explained

[utzoo!decvax!harpo!seismo!dmy]

I received 10 mail responses to my "Simple C Puzzle" posting.  Almost everyone
solved it. (I said it was simple.)  One person used lint (try it), and another
said some compilers would give a warning anyway.  Comments ranged from "too
easy" to "neat trick" to "my compiler produces 2" (so it's not only a legitimate
puzzle, it's useful as a compiler test case).

The solution (someone's already posted it) is that a/*p is parsed as "a"
followed by the beginning of a comment, rather than as "a / *p" (which effect
is achieved by the addition of propitious spacing).  Thus the "++a" is part of
a comment and not executed.  The real "puzzle" was to invent such an ambiguous
case without being too obvious about it.

Any other interesting c (or inferior language) relatively short puzzles out
there?  Post to the net -- they are probably of general interest.
(Don't bother plagarizing the Puzzle Book).

--dmy--