Rainer Deyke Wrote:
> On 8/10/2010 16:59, foobar wrote:
> > Steven Schveighoffer Wrote:
> >> what happens when GC destroys a C?
> >>
> >> C::~this(); // auto generated
> >> B::~this(); // so good so far
> >> A::~this(); // oops! the a is gone, program vomits bits all over
> >> itself and
> >> chokes to death.
> >>
> >> -Steve
> >
> > This can only happen if you use delete on a class instance. My
> > understanding was that this is going to be removed from D2.
>
> Same problem without 'delete':
>
> class A {
> void dispose();
> }
>
> struct B {
> A a;
> ~this() { a.dispose(); }
> }
>
> class C {
> B b;
> }
>
> C::~this(); // auto generated
> B::~this(); // so good so far
> A::dispose(); // oops!
>
>
> --
> Rainer Deyke - rain...@eldwood.com
I was posing late at night and hence made a mistake in my suggestion.
Here's a better example of the problem:
class A{}
struct B{ A a; ~this(); this(ref A); }
auto obj = new A();
auto first = new B(obj);
auto second = new B(obj);
both first and second reference the same instance of A.
The correct semantics for the case of a struct containing a class (more
generally, value type contains a reference type):
the struct's dtor does NOT call the class dtor.
The class dtor would be called either by the GC when it is collected or when it
is de-allocated by the user when its memory is managed by a different memory
scheme.
Sorry for this confusion, it'll teach me not to post at 2AM..
