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From: jsdy@hadron.UUCP (Joseph S. D. Yao)
Newsgroups: net.lang.c
Subject: Cpp: if/else/else/endif?????
Message-ID: <143@hadron.UUCP>
Date: Wed, 25-Dec-85 11:18:53 EST
Article-I.D.: hadron.143
Posted: Wed Dec 25 11:18:53 1985
Date-Received: Sat, 28-Dec-85 01:04:07 EST
Reply-To: jsdy@hadron.UUCP (Joseph S. D. Yao)
Organization: Hadron, Inc., Fairfax, VA
Lines: 24
Keywords: cpp, #ifdef, #else
Summary: Unexpected extra else behaviour

[I don't believe in line-eaters, and refuse to feed theMUNCH

I noticed something rather peculiar, in kernel (network) code
no less.  If you have multiple #else's between an #ifdef and
the #endif ... they work!  That is, given input like:
	#ifdef	X
		X is
	#else
		X is not
	#else
		X is
	#endif
then, cpp'ed with no X you get
		X is not
and cpp'ed with -DX, you get
		1 is
		1 is
If anybody out there has a cpp that does  n o t  do this, please
e-mail to me (do not post!) and I will summarise.  [Extra garbage
like #line's or blank lines doesn't count, because they were there
and I edited them out.]
-- 

	Joe Yao		hadron!jsdy@seismo.{CSS.GOV,ARPA,UUCP}