Date: Wed, 6 Nov 2002 18:03:25 +0100 From: Erik Trulsson <ertr1013@student.uu.se> To: John Baldwin <jhb@FreeBSD.org> Cc: Marc Olzheim <marcolz@stack.nl>, hackers@FreeBSD.org Subject: Re: RE: /usr/src/ed/bin/re.c:99 Message-ID: <20021106170325.GB19789@student.uu.se> In-Reply-To: <XFMail.20021106115417.jhb@FreeBSD.org> References: <20021106164653.GA95733@stack.nl> <XFMail.20021106115417.jhb@FreeBSD.org>
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On Wed, Nov 06, 2002 at 11:54:17AM -0500, John Baldwin wrote:
>
> On 06-Nov-2002 Marc Olzheim wrote:
> > ..
> > if ((nd = parse_char_class(++nd)) == NULL) {
> > ..
> >
> > Hmmm... is this legal ?
> >
> > http://www.eskimo.com/~scs/C-faq/q3.1.html seems to tell otherwise...
>
> If it were nd++, yes. However, it is ++nd, thus, the increment
> happens first, then the call to parse_char_class(), then the assignment
> to nd. It might be clearer to rewrite this like so however:
In this regard nd++ and ++nd are completely equivalent. If parse_char_class
is a function (and not a macro) I think the expression might be legal
anyway since there is a sequence point after evaluating the arguments for
a function call and making the call.
If, OTOH, parse_char_class is a macro then the above expression is
definitely not legal.
(It is not legal to modify an object more than once without a sequence
point in between.)
>
> if ((nd = parse_char_class(nd + 1)) == NULL) {
>
> Since that is effectively what it is doing.
Yes, that would be clearer and definitely legal.
--
<Insert your favourite quote here.>
Erik Trulsson
ertr1013@student.uu.se
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