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Re: i think i found

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jgk@panix.com (Joe keane) writes:
> In article <ea3cda64-a914-4f34-ba2a-59df5fb9fc93@m13g2000yqi.googlegroups.com>,
> Barry Schwarz  <schwarz45@yahoo.com> wrote:
>>Since your sample code does not have any arrays of arrays, we have no
>>idea what your question is.
>
> OK
>
>     int f(int x)
>     {
> 	int a[2][2];
> 	int *p;
>
> 	p = &a[0][0];
> 	*p = 1;
> 	p += 2;
> 	*p = 2;
> 	--p;
> 	*p = 3;
> 	p += 2;
> 	*p = 4;
> 	/* printf(...); */
> 	return 0;
>     }

Great, you've posted some more code.  Did you want to say something
about it?  Your subject header is "i think i found".  What exactly do
you think you've found?

I'm sure the point you're making is clear to you, but you're not
conveying it well to the rest of us.

As for the code you posted, its behavior is undefined.  "p" is an "int*"
that's initialized to point to element 0 of a 2-element array a[0]
(which happens to be an element of a larger array).  "p += 2" causes it
to point just past the last element of the array a[0], which is ok.  But
the "*p = 2;" assigns a value past the end of that array, which has
undefined behavior.

N1570 section J.2 has a (non-normative) list of undefined behaviors, one
of which is:

    An array subscript is out of range, even if an object is apparently
    accessible with the given subscript (as in the lvalue expression
    a[1][7] given the declaration int a[4][5]) (6.5.6).

So what was your question?

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
    Will write code for food.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

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i think i found jgk@panix.com (Joe keane) - 2012-03-10 01:09 +0000
  Re: i think i found Ian Collins <ian-news@hotmail.com> - 2012-03-10 14:23 +1300
  Re: i think i found nick_keighley_nospam@hotmail.com - 2012-03-10 03:13 -0800
  Re: i think i found Barry Schwarz <schwarz45@yahoo.com> - 2012-03-10 09:17 -0800
    Re: i think i found pete <pfiland@mindspring.com> - 2012-03-10 19:22 -0500
      Re: i think i found James Kuyper <jameskuyper@verizon.net> - 2012-03-10 20:14 -0500
        Re: i think i found pete <pfiland@mindspring.com> - 2012-03-10 21:59 -0500
      Re: i think i found jgk@panix.com (Joe keane) - 2012-03-12 17:29 +0000
    Re: i think i found jgk@panix.com (Joe keane) - 2012-03-11 19:35 +0000
      Re: i think i found Keith Thompson <kst-u@mib.org> - 2012-03-11 13:06 -0700
        Re: i think i found jgk@panix.com (Joe keane) - 2012-03-13 20:27 +0000
          Re: i think i found Keith Thompson <kst-u@mib.org> - 2012-03-13 15:25 -0700
            Re: i think i found jgk@panix.com (Joe keane) - 2012-03-14 23:34 +0000
              Re: i think i found Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-03-14 20:38 -0400
              Re: i think i found Tim Rentsch <txr@alumni.caltech.edu> - 2012-03-15 18:03 -0700
                Re: i think i found jgk@panix.com (Joe keane) - 2012-03-17 17:34 +0000
                Re: i think i found Keith Thompson <kst-u@mib.org> - 2012-03-17 18:02 -0700
                Re: i think i found jgk@panix.com (Joe keane) - 2012-03-19 15:41 +0000
                Re: i think i found Tim Rentsch <txr@alumni.caltech.edu> - 2012-03-21 05:52 -0700

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