From mboxrd@z Thu Jan  1 00:00:00 1970
To: 9fans@cse.psu.edu
Subject: Re: [9fans] PCC - #if
From: "Russ Cox" <rsc@swtch.com>
Date: Fri,  4 May 2007 17:57:23 -0400
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> So if I have
> 
> 	#undef	C
> 
> followed by
> 
> 	#if		C
> 
> is it valid or invalid?  Your explanation leaves it unclear (or I
> missed it, somehow).

It is valid.  `#if C' macro-expands to `#if C' (no change)
and then all names in #if expressions turn into 0s, so it
is treated as `#if 0'.

Russ