Re: PR 25512: pointer overflow defined?

[Andrew Haley <aph at redhat dot com>]

Richard Guenther writes:
 > On Wed, 21 Dec 2005, Andrew Haley wrote:
 > 
 > > Richard Guenther writes:
 > >  > 
 > >  > The problem in this PR is that code like in the testcase (from
 > >  > OpenOffice) assumes that pointer overflow is defined.  As the
 > >  > standard does not talk about wrapping pointer semantics at all (at
 > >  > least I couldn't find anything about that), how should we treat
 > >  > this?
 > > 
 > > Look at Section 6.5.6, Para 8.  The code is undefined.
 > 
 > This talks about pointers that point to elements of an array
 > object.  It does not talk about doing arithmetic on arbitrary
 > pointer (constants), which is what the code does.  Or is a pointer
 > always pointing to elements of some array object (being it the
 > global heap "array object")?

Section 6.5.6, Para 8 always holds.  If p1 is a valid pointer, then it
points to a byte within an object or to an element just past the end
of an array.

Andrew.