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Re: Pointers and Sequence Point

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Kenneth Brody <kenbrody@spamcop.net> writes:

> On 5/2/2011 9:58 AM, Martin Ambuhl wrote:
> > On 5/2/2011 7:38 AM, arnuld wrote:
> >> I have this program which is causing confusion to me. I am told that last
> >> printf() of main() will always print "Second", not "First". I think line:
> >>
> >> x = myAlloc(x);
> >
> > While it is possible to write evil code in which myAlloc could modify x, in
> > C myAlloc receives a copy of the value of x and has no clue where x is or
> > how to modify it. There are not two or more instances of modifying x between
> > sequence points.
> 
> But, unless I'm badly mistaken (and I know I'll be told so if I am),
> the call to and a return from a function are sequence points.
> Therefore, as long as myAlloc() is a function and not a macro, even
> this does not invoke UB:
> 
>      x = myAlloc(x++);
> 
> >> is UB. My colleague is disagreeing on this while I was saying that its UB
> >> because there is no sequence point here. It is just like using this line:
> 
> The function call is a sequence point.

At least 2. One between the evaluation of the parameters and the call, and 
one at the return of the function.

Phil
-- 
"At least you know where you are with Microsoft."
"True. I just wish I'd brought a paddle." -- Matthew Vernon

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Pointers and Sequence Point arnuld <sunrise@invalid.address> - 2011-05-02 11:38 +0000
  Re: Pointers and Sequence Point James Kuyper <jameskuyper@verizon.net> - 2011-05-02 08:23 -0400
  Re: Pointers and Sequence Point Martin Ambuhl <mambuhl@earthlink.net> - 2011-05-02 09:58 -0400
    Re: Pointers and Sequence Point Chad <cdalten@gmail.com> - 2011-05-02 09:36 -0700
      Re: Pointers and Sequence Point Angel <angel+news@spamcop.net> - 2011-05-02 17:21 +0000
      Re: Pointers and Sequence Point James Kuyper <jameskuyper@verizon.net> - 2011-05-02 23:20 -0400
        Re: Pointers and Sequence Point Keith Thompson <kst-u@mib.org> - 2011-05-02 23:26 -0700
          Re: Pointers and Sequence Point James Kuyper <jameskuyper@verizon.net> - 2011-05-03 05:33 -0400
    Re: Pointers and Sequence Point Kenneth Brody <kenbrody@spamcop.net> - 2011-05-02 13:35 -0400
      Re: Pointers and Sequence Point Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2011-05-03 17:45 +0300
  Re: Pointers and Sequence Point John Bode <jfbode1029@gmail.com> - 2011-05-02 10:17 -0700
  Re: Pointers and Sequence Point Tim Rentsch <txr@alumni.caltech.edu> - 2011-05-02 10:31 -0700
  Re: Pointers and Sequence Point "Morris Keesan" <mkeesan@post.harvard.edu> - 2011-05-02 20:55 -0400
    Re: Pointers and Sequence Point David Resnick <lndresnick@gmail.com> - 2011-05-03 08:01 -0700

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