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From: lehners@uniol.UUCP (Joerg Lehners)
Newsgroups: comp.lang.c
Subject: Re: quotes inside #if 0
Keywords: ANSI, comments
Message-ID: <830@uniol.UUCP>
Date: 6 Sep 89 22:41:27 GMT
References: <2014@munnari.oz.au> <14512@haddock.ima.isc.com> <2023@munnari.oz.au> <766@ecrcvax.UUCP>
Organization: University of Oldenburg, W-Germany
Lines: 35

diomidis@ecrcvax.UUCP (Diomidis Spinellis) writes:
>[some text deleted]

>ecrcvax% cat t.c
>#if 0
>#funny_text
>/*
>#endif
>ecrcvax% /bin/cc -c t.c
>t.c: 2: undefined control
>t.c: 5: unterminated comment

>Vanila pcc complains about unbalanced comments and undefined preprocessor
>controls inside #if 0 blocks.  Commenting out arbitrary text with #if 0 is
>not a safe practice for most compilers (both ANSI and classic C).

I think the preprocess must look at the code following the #if 0 because
the preprocessor must look for the corresponding #endif.
And the rules for the preprocessor are: don't do any substitutions
an interpretation in constant character arrays (""),
character constants ('') and comments (/* */).

But the idea of non-interpreting #if 0 / #endif pairs would be very nice:
to (totally) comment out a full chunk of nontestet, non " and '
balanced code but /* */ balanced code, without worrying about recursive
comments.

  Joerg
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