Robert Elz wrote:

>     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"

Yes, it has always worked in Unix based cpp.  It is still abuse. :-)
(It hasn't always worked in other cpps.)

    -- Lennart