Re: Inconsistent hierarchy

["Jerry Miller" <gmiller at cs dot sunysb dot edu>]

----- Original Message -----
From: David Korn <dkorn@pixelpower.com>
To: 'Jerry Miller' <gmiller@cs.sunysb.edu>; <help-gcc@gnu.org>
Sent: Friday, February 23, 2001 12:47 PM
Subject: RE: Inconsistent hierarchy


> >-----Original Message-----
> >From: Jerry Miller [mailto:gmiller@cs.sunysb.edu]
> >Sent: 22 February 2001 03:31
>
>  [Rather an old one, but better late than never]
>
> >It turns out that the string '/|\' is valid under PL/I, but
> >it escapes the second single-quote under C.  However,
> >the compiler seems to have no business whatsoever
> >parsing something whose #ifdef condition has not been
> >met.  It appears that the respective hierarchies of the
> >quote symbol and the #ifdef/#endif pair are reversed
> >between these two versions, and according to my own
> >perception, it is the PC version whose behavior seems
> >more intuitive.
>
>   Well, there would be a slight problem with that: if you stop parsing
> the moment you hit a #if 0, how do you know when to start parsing again?
> At the very least you'd have to watch out for the #endif; and of course
> you've got to watch out for nested #if-#endif pairs, so that you don't
> start parsing again too easily, and it gets complex very quickly.
-----------------------------
I guess that's true.  Even if a directive must be the first thing on the
line, a string can continue on a new line, particularly if the preceding
line ends with a backslash.

The main reason for my confusion was that two gcc implementations
handle the situation differently.
-----------------------------
>
>   I believe the C language standard actually specifies that everything
> in the source file must be valid C preprocessing tokens, even if it is
> enclosed in a #if 0.  It isn't to do with 'hierarchies' (I assume you
> mean something like operator precedence here), and if it doesn't happen
> on a newer version of the compiler I assume that means that somebody got
> annoyed and did something about it.
------------------------
Yes, "precedence" is the word I was looking for.  Just another of my
"senior moments" when my whaddyacallit goes blank for a while!
------------------------
>
>   I ran across this problem for myself quite a while ago, since I used
> to like doing stuff like...
>
> #if 0
>
>     ... code ...
>
>  aha this code isn't finished yet so I shall use if 0 to stop it compiling
>
> #endif
>
> and the preprocessor complained about my unterminated character constant,
> having taken the ' in "isn't" for the opening apostrophe of a character
> constant.
>
>   This isn't really a solution to your problem, because there isn't one
> except to watch out for and correct those apostrophes as you encounter
> them; sorry.
>
>       DaveK
> --
> we are not seats or eyeballs or end users or consumers.
> we are human beings - and our reach exceeds your grasp.
>                     deal with it.                      - cluetrain.org
>
>
> **********************************************************************
> This email and any files transmitted with it are confidential and
> intended solely for the use of the individual or entity to whom they
> are addressed. If you have received this email in error please notify
> the system manager.
>
> This footnote also confirms that this email message has been swept by
> MIMEsweeper for the presence of computer viruses.
>
> www.mimesweeper.com
> **********************************************************************
>