On Fri, Feb 27, 2009 at 09:10:10AM +0100, Mathieu Lacage wrote:
> - if you want to use the stack protector and split stacks, it should
> be fairly trivial to extend the data structure which contains the stack
> protector with a new field, no ?
The stack protector is just a word, not a pointer. It's held in a
highly magic location on some platforms, e.g. relative to the thread
base register. There's not a lot of space there. It might be
possible to reserve more in coordination with glibc, for glibc
targets.
> - I understand that you need to copy the function parameters from the
> old stack to the new stack, but, why would you need to invoke the C++
> copy or move constructors for this ? Would a memcpy not be sufficient to
> ensure proper C++ semantics in this case ? An example which shows how a
> memcpy would break might be interesting.
I haven't written C++ in a while, so forgive any obvious gaffes.
class X {
int x, *y;
X() {
y = &x;
}
X(X &obj) {
x = obj.x;
y = &x;
}
}
Memcpy that somewhere else and the internal pointer is invalid.
--
Daniel Jacobowitz
CodeSourcery
