Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!usc!elroy.jpl.nasa.gov!jarthur!dfoster
From: dfoster@jarthur.Claremont.EDU (Derek R. Foster)
Newsgroups: comp.lang.c
Subject: Re: Re^4: Why nested comments not allowed?
Message-ID: <4601@jarthur.Claremont.EDU>
Date: 23 Feb 90 21:52:28 GMT
References: <4015@hub.UUCP> <4550@jarthur.Claremont.EDU> <10837@june.cs.washington.edu>
Organization: Harvey Mudd College, Claremont, CA 91711
Lines: 40

In article <10837@june.cs.washington.edu> machaffi@fred.cs.washington.edu.cs.washington.edu (Scott MacHaffie) writes:
>In article <4550@jarthur.Claremont.EDU> dfoster@jarthur.Claremont.EDU (Derek R. Foster) writes:
>>The only real reasons there are to do this (put /* or */ in strings) are: 
>
>You forgot "writing a C parser which has to recognize comments".
>
>			Scott MacHaffie

No, I didn't. You missed the point of my statement. (Don't feel bad; several
other people did too. That's why I'm posting instead of e-mailing you.
Most of the criticisms that I have heard have come from people that
simply misunderstood what I was saying. Was I really that unclear?)

I wasn't saying that these characters should never be used as string data.
I said that they should not be placed LITERALLY in a string, since they may
be mistaken (by the parser) for comments. (Literally as in, "inside quotation
marks, a '*' followed IMMEDIATELY by a '/' or vice versa"). Since the parser
will only recognize these characters as a comment if it sees them one right
after the other, encoding

  printf("before comment /* comment */ after comment");

in some way that breaks up the /* and */ pairs (but still means the same
thing to the compiler, just not the parser) means that the parser won't
ever mistake them for comments. I have posted several suggestions on how
to do this, but in case you missed them, my favorite so far is this:

  #define CS "/""* "
  #define CE " *""/"
  .
  .
  .
  printf("before comment"CS"comment"CE"after comment");

Note that although these lines produce code that is functionally identical
to the first printf, at no point in the code do the characters '/*' or '*/'
appear as literal strings. Therefore, they won't be recognized by the parser
as comments, and so won't cause you problems later on. 

Derek Foster