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From: philip@Kermit.Stanford.EDU (Philip Machanick)
Newsgroups: comp.sys.mac.programmer
Subject: Re: MPW 2.0 and 3.0/3.1
Message-ID: <1990May9.181805.10891@Neon.Stanford.EDU>
Date: 9 May 90 18:18:05 GMT
References: <3238@rodan.acs.syr.edu>
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Reply-To: philip@pescadero.stanford.edu
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Organization: Computer Science Department, Stanford University
Lines: 41

In article <3238@rodan.acs.syr.edu>, dinapoli@rodan.acs.syr.edu (Ron
DiNapoli) writes:
> ... advised me to upgrade to MPW C 3.1.  I did this, but the problem 
> did not go away.  Well I finally discovered what was going wrong... I had the
> following macro defined:
> 
> 	#define OP(tkdef,tkname,d1,d2) {#tkdef,tkname,d1,d2}
> 
> and I wanted to expand the following:
> 
> 	OP(TK_SSLASH,"//",ASSC_YFX,400)
> 
> Anybody see the problem?  In MPW C 3.0 and later, the '//' symbol stands
> for a comment.  It also seems that the preprocessor is unable to detect
> that this particular comment character is occurring within a string.  
> Since it doesn't, the preprocessor sees the open end of a string, and never
> finds the closing " (because the real one was 'commented' out) before its
> internal buffer overflows.  Once discovered, the fix was easy.  I just 
> changed this particular occurrance of OP to:
> 
> 	OP(TK_SSLASH,"/\/",ASSC_YFX,400)
> 
> 
> So, it this a bug?  In my opinion it isn't.  Take for example the following 
> macro definition:
[example deleted]
> Note how in the first occurrance of the PRINTIT macro, the text between the
> /* */ comment characters does not appear.  This tells me that in the 3.0/3.1
> C preprocessor, comments are "taken out" regardless of where they appear.
> Thus my problems with the '//' in my string seems consistent with this
> philosophy.  For this reason, I would say it is not a bug at all!

From Kernighan and Richie (2nd edition; p. 192):
"  Comments do not nest, and they do not occur within string or
   character literals.             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
"  ^^^^^^^^^^^^^^^^^^
I haven't checked the behaviour you reported, but if MPW C 3 behaves as
you suggest it does, this IS a bug.

Philip Machanick
philip@pescadero.stanford.edu