Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!samsung!munnari.oz.au!goanna!ok
From: ok@goanna.oz.au (Richard O'keefe)
Newsgroups: comp.lang.c
Subject: Re: Re^2: Why nested comments not allowed?
Summary: ANSI rule
Message-ID: <2899@goanna.oz.au>
Date: 22 Feb 90 04:50:55 GMT
References: <1523@wacsvax.OZ> <13706@cbnewsc.ATT.COM> <4286@jhunix.HCF.JHU.EDU> <5372@ur-cc.UUCP>
Organization: Comp Sci, RMIT, Melbourne, Australia
Lines: 23

In article <5372@ur-cc.UUCP>, misu_ss@uhura.cc.rochester.edu (What`s in a name?) writes:
> This leads me to a question on how compilers work...
> Do #defines get worked out before comments are discarded...

It is quite explicit in ANSI C that comments are turned into spaces before
any preprocessor directives are recognised or processed.

In older C systems, particularly ones based on the "Reiser" preprocessor,
this wasn't true, but portable code never could exploit it so we haven't
lost anything.

A consequence of the ANSI rules is that

	#define OPEN_COMMENT /*
	extern int fred[];
	/* static */ int tom[2];

acts exactly like

	#define OPEN_COMMENT   int tom[2];

If you want to do hairy things with comments and macros, M4 comes as
part of the UNIX toolkit, and there's a PD implementation in C.