On 1/27/07, Paul Schlie <[EMAIL PROTECTED]> wrote:
>> On Fri, Jan 26, 2007 at 06:57:43PM -0500, Paul Schlie wrote:
> Likewise, if the program has an uninitialized variable, the behavior
> will differ depending on details of optimization and how variables are
> assigned to memory. Heap allocated for the first time might always be
> zero (as the OS delivers it that way), turning on optimization might then
> result in a nonzero initial value because of reuse of a register.
- I would argue that in this circumstance although the resulting value may
differ, the results are actually equivalent; as in both circumstances the
value returned is the value associated with it's storage location; and as
the value of all storage locations are arbitrary unless otherwise well
specified; the result may change from run to run regardless of any applied
optimizations.
If you read from an uninitialized variable twice you might as well get
a different result each time. This is exactly the same issue than with
signed overflow and observable behavior - though as somebody notes
later - the uninitialized variable case doesn't stir up too many peoples
mind.
Richard.
