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From: shankar@hpclscu.HP.COM (Shankar Unni)
Newsgroups: comp.lang.c++
Subject: Re: Re: f***ing comments -- another pitfall to avoid
Message-ID: <58170022@hpclscu.HP.COM>
Date: 30 May 90 18:53:36 GMT
References: <31891@sparkyfs.istc.sri.com>
Organization: Hewlett-Packard Calif. Language Lab
Lines: 43

> I sympathize with your interpretation of how commentmacro should
> be expanded, but I dislike the results, to say the least!  The effect
> is that the first ``//'' comment encountered throws the rest of the
> macro definition away.  If ``//'' comments are to be useful inside
> of macros, they should delete the text up to, but not including, the
> first occurance of either a newline or a backslash immediately preceding
> a newline.
> 
> This does not really conflict with the ANSI C standard, since ANSI C
> does not have ``//'' comments.  C++ would of course need to define
> the interaction explicitly -- the current smorgasborg of behaviors
> is no doubt in part due to the lack of explicit definition.

And I sympathise with your "DWIM" interpretation.

But remember: a macro definition is technically ONE line. If you embed a
"//" comment in there, tough luck: you just lost the rest of the line.
Would you embed a "//" comment in the middle of a function call list, like
so:

   foo (x // comment, y, z)?

What is the difference between this, and what you are trying to do with
your macro?

Remember, there is a place for /**/ comments and a place for // comments.
The "old-style" comments are by no means second-class in C: they are
intended to be used in exactly the situation that you describe:

  #define longmacro   line         /* comment */ \
  		      line         /* comment */ \
		      line         /* comment */

The most logical (and in my opinion, correct) way to handle macro
definitions is to do it as follows:

   - pull in everything upto a unescaped newline (deleting all \<newline>s).
   - process comments (i.e. strip out /**/  and // comments)

-----
Shankar Unni                                   E-Mail: 
Hewlett-Packard California Language Lab.     Internet: shankar@hpda.hp.com
Phone : (408) 447-5797                           UUCP: ...!hplabs!hpda!shankar