Re: Y21C Bug

[Mats Weber <matsw@mail.com>]

Thierry Lelegard wrote:

> Yes it does. If you had left the variable uninitialized (on an Ada
> perspective), then the variable would have been allocated in
> a "demand zero" section (no allocation in executable). Since
> you provided an explicit initial value, the compiler/linker placed
> it into a "copy on reference" section which contains the initial
> values. Of course, the compiler could make a special optimization
> which consists in inspecting every single byte of this initial
> value and if they are all zeroes then place the variable into
> a "demand zero" section. But, it appears that this optimization
> is not made.

You generally cannot guarantee that the variable is allocated in a
demand-zero region. For instance, when allocated on the stack, the stack
may have previously grown higher than where you allocate and you get the
content left there from a previous call (unless the stack is zeroed or
unmapped from the address space when it shrinks, but I doubt any system
is doing that).