How do I properly implement object destruction of extern(C++) classes (with
virtual destructors)?

I'm not going to embarrass myself by pasting some of my attempts to achieve
this goal to date.
I've asked before, but I've never yet seen a sufficiently solution to this
problem.

Situation:

I have a C++ base class expressed by an extern(C++) class.
C++ base class has virtual destructor.
I derive both C++ and D classes from this base class, they must each
destruct properly in their own right (object.destroy() crashes).
D passes base class pointers of D-derived classes to C++, and C++ calls the
virtual destructor.
D receives C++-derived classes by base class pointer, and needs to call the
virtual destructor (attempting to use object.destroy() crashes).

Forget about memory allocation, that's a separate (and solved) problem. The only concern is proper destruction.

Can anyone who has had success in this space demonstrate how to structure such code that will work?

Here is a C++ base class:

class Base
{
  virtual ~Base() { printf("destructing base"); }
};

I leave the rest of the puzzle as a clean slate. My attempts are all disasters.

Note: I am happy to re-implement the C++ base class destructors on the D size, as I expect that's necessary when derived D classes want to call their base destructors.

On Thursday, 22 June 2017 at 12:52:26 UTC, Manu wrote:
> How do I properly implement object destruction of extern(C++) classes (with
> virtual destructors)?
>
> I'm not going to embarrass myself by pasting some of my attempts to achieve this goal to date.

I take it you tried calling super.~this() already? that would be my first thought.

Nicholas Wilson wrote:

> On Thursday, 22 June 2017 at 12:52:26 UTC, Manu wrote:
>> How do I properly implement object destruction of extern(C++) classes (with
>> virtual destructors)?
>>
>> I'm not going to embarrass myself by pasting some of my attempts to achieve this goal to date.
>
> I take it you tried calling super.~this() already? that would be my first thought.

that won't work, 'cause `~this` is not a valid symbol. yet `super.__dtor()` will work.

On Thursday, 22 June 2017 at 12:52:26 UTC, Manu wrote:
> How do I properly implement object destruction of extern(C++) classes (with
> virtual destructors)?
>
> [...]

Also didn't Ethan come up with a solution for this for Binderoo?

On 23 June 2017 at 09:32, Nicholas Wilson via Digitalmars-d < digitalmars-d@puremagic.com> wrote:

> On Thursday, 22 June 2017 at 12:52:26 UTC, Manu wrote:
>
>> How do I properly implement object destruction of extern(C++) classes
>> (with
>> virtual destructors)?
>>
>> [...]
>>
>
> Also didn't Ethan come up with a solution for this for Binderoo?
>

I'm not sure...

On Friday, 23 June 2017 at 00:33:55 UTC, Manu wrote:
> On 23 June 2017 at 09:32, Nicholas Wilson via Digitalmars-d < digitalmars-d@puremagic.com> wrote:
>
>> On Thursday, 22 June 2017 at 12:52:26 UTC, Manu wrote:
>>
>>> How do I properly implement object destruction of extern(C++) classes
>>> (with
>>> virtual destructors)?
>>>
>>> [...]
>>>
>>
>> Also didn't Ethan come up with a solution for this for Binderoo?
>>
>
> I'm not sure...

I'm pretty sure he manually constructs the vtbl and inserts the virtual function into it, so it should just be a case of calling the virtual destructor.

Have a look at this DConf 2017 talk.

On Fri, Jun 23, 2017 at 10:52 AM, Nicholas Wilson via Digitalmars-d < digitalmars-d@puremagic.com> wrote:

>
>>
> I'm pretty sure he manually constructs the vtbl and inserts the virtual function into it, so it should just be a case of calling the virtual destructor.
>
> Have a look at this DConf 2017 talk.
>

He is mapping C++ classes onto D structs IIRC.

On 23 June 2017 at 10:52, Nicholas Wilson via Digitalmars-d < digitalmars-d@puremagic.com> wrote:

> On Friday, 23 June 2017 at 00:33:55 UTC, Manu wrote:
>
>> On 23 June 2017 at 09:32, Nicholas Wilson via Digitalmars-d < digitalmars-d@puremagic.com> wrote:
>>
>> On Thursday, 22 June 2017 at 12:52:26 UTC, Manu wrote:
>>>
>>> How do I properly implement object destruction of extern(C++) classes
>>>> (with
>>>> virtual destructors)?
>>>>
>>>> [...]
>>>>
>>>>
>>> Also didn't Ethan come up with a solution for this for Binderoo?
>>>
>>>
>> I'm not sure...
>>
>
> I'm pretty sure he manually constructs the vtbl and inserts the virtual function into it, so it should just be a case of calling the virtual destructor.
>
> Have a look at this DConf 2017 talk.
>

I do that, but that doesn't mean the destructors work. object.destroy()
just crashes.

Believe me, I've been messing with this a lot. The answer to this email is some code that satisfies the criteria, I've tried a lot of things.

On 23 June 2017 at 13:45, Danni Coy via Digitalmars-d < digitalmars-d@puremagic.com> wrote:

>
>
> On Fri, Jun 23, 2017 at 10:52 AM, Nicholas Wilson via Digitalmars-d < digitalmars-d@puremagic.com> wrote:
>
>>
>>>
>> I'm pretty sure he manually constructs the vtbl and inserts the virtual function into it, so it should just be a case of calling the virtual destructor.
>>
>> Have a look at this DConf 2017 talk.
>>
>
> He is mapping C++ classes onto D structs IIRC.
>

Oh yeah that's right, that's a totally different ball-game :)