Date:        Fri, 30 Nov 2001 09:34:22 +0100
    From:        Lennart Augustsson <lennart@augustsson.net>
    Message-ID:  <3C07448E.149D0DF8@augustsson.net>

  | > There's a number of places in the kernel where we assume that an
  | > undefined flag == 0 in preprocessor expressions, some of them to test
  | > if just one of the tokens is defined.  Is it actaully _abuse_ of the
  | > preprocessor, or defined(!) behaviour?
  | 
  | Well, in the past it has always been abuse.

No it isn't

	#undef thing

	#if thing > 1

has always been interpreted as "#if 0 > 1"

I think K&R (2, #if didn't exist in K&R 1 I don't think) might have even
said so, but my copy isn't here for me to check.

kre