Re: Signed int overflow behavior in the security context

[James Dennett <jdennett at acm dot org>]

Paul Schlie wrote:
>> Brooks Moses wrote:
>> <http://gcc.gnu.org/ml/gcc/2007-01/msg01119.html> ...
>> Does that logic work for you?
> 
> no, as although a variable's value may not have been previously defined
> within the context of a particular program, a variable's access semantics
> are orthogonal to what ever value may result from that variable's access;

No; it's not just the value that is undefined; it's the
behavior of code attempting to use that value that is
undefined.  Aborting the program is quite conforming if
your program uses "the value" of an uninitialized int,
for example.  I write "the value" in quotes because the
variable does not *have* a value until one is assigned
to it.  The fact that storage allocated for the variable
holds some bit pattern shouldn't be confused with that
variable having a value; so long as the variable has not
been given a value, the compiler might read it from
anywhere or nowhere, and has no obligation to be
consistent.  I've seen no justification for any claim
that there is an obligation on the compiler to produce
consistent values in this situation; the C standard, on
the other hand, states quite clearly that code *cannot*
rely on any such thing.

-- James