Path: utzoo!utgpu!water!watmath!clyde!cbosgd!ucbvax!hoptoad!gnu
From: gnu@hoptoad.uucp (John Gilmore)
Newsgroups: comp.lang.c
Subject: Re: nested comments
Message-ID: <3929@hoptoad.uucp>
Date: 25 Jan 88 15:40:51 GMT
References: <13423@pyramid.pyramid.com> <7937@eddie.MIT.EDU>
Organization: Nebula Consultants in San Francisco
Lines: 30

jbs@eddie.MIT.EDU (Jeff Siegal) wrote:
> #ifdef COMPILE_BROKEN_CODE
> 
> 	... broken code ...
> 
> #endif

Unfortunately, ANSI C makes this less likely to work.  The old Unix
preprocessor ignored ' and " inside #ifdef's, so you really could
#ifdef out just about anything you wanted, other than unterminated
/* comments.  But you might argue that it errs on stuff like this:

#ifdef FOO
	printf("\
#endif FOO\
\n");

since it terminates the #ifdef at the #endif.  Indeed, ANSI C
says that the #endif does NOT terminate the #ifdef.  The problem
is that old code assumed it could put ' and " in #ifdef 0's;
in particular it gets used for commentary that includes "can't"
or "didn't" or other uses of unmatched single quotes; and the C
preprocessor is also used on assembler sources, which use ' singly
rather than in pairs (at least in the Vax assembler).

So you'd better be sure that at least the quotes line up in your
"broken code" before you #if 0 or #ifdef NOTDEF it away...
-- 
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