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From: scott@cs.ua.oz.au (Scott Davis)
Newsgroups: comp.lang.c++
Subject: Re: "//" comments and #define's : problems
Message-ID: <SCOTT.89Jul21165720@chook.ua.oz.au>
Date: 21 Jul 89 07:27:20 GMT
References: <1000019@hpclscu.HP.COM>
Sender: news@sirius.ua.oz
Organization: Computer Science, Adelaide University, Australia
Lines: 60
In-reply-to: shankar@hpclscu.HP.COM's message of 11 Jul 89 17:06:50 GMT

In article <1000019@hpclscu.HP.COM> shankar@hpclscu.HP.COM (Shankar Unni) writes:
>   When fixing up a "cpp" to handle "//"-style comments, I came across an
>   interesting problem.
>
>   Comments on #define's are preserved by cpp when sucking up the define, and
>   later, after substitution, subsequent rescans of the line simply strip out
>   the comment. (This is how it makes token-pasting, etc work).
>
>	[further discussion of problem]
>
>   Question:
>
>   How should a "//"-comment on a #define work?
>
>     (a) Completely stripped out when processing #define. Not passed through
>	 even when requesting "pass comments". (This is my preference).
>
>     (b) Leave it as is. I.e. specify that a "//"-comment on a #define will
>	 have "undefined" (i.e. nasty and unpredictable) effects. Warn the user
>	 when detected.
>
>     (c) Do some fudge like have "cpp" insert a "/*" and "*/" around the
>	 "//"-style comment, as in
>
>	 x b /* // comment */ y
>
>   This is one more reason to adopt a *standard* cpp (preferably an ANSI C 
>   style cpp), with well-defined "//"-comment semantics.
>

What about:
      (d) Insert the carriage return which terminates the comment as well, as
in 
	x b // comment
	y

OK, so this doesn't look quite the same, but at least it is semantically
correct, and the comments *are* still there if you want to read them.

This is the method I would expect, as the comment is terminated by end of line,
it doesn't just fade off to some indeterminate point. The Carriage return is as
much a part of the comment as the '//' which started it.

You don't strip off the */ from the end of a C-style comment, just leaving the
/* at the beginning, so why treat C++-style comments any different?

Comments?

Scott.
--
Scott Davis				ACSnet: scott@cs.ua.oz{.au}
Honours student,			 other: scott@cs.ua.oz@uunet.uu.net
Department of Computer Science,
University of Adelaide.
Australia.
--
Scott Davis				ACSnet: scott@cs.ua.oz{.au}
Honours student,			 other: scott@cs.ua.oz@uunet.uu.net
Department of Computer Science,
University of Adelaide.