[v2 02/10] msvcirt: Implement ostream constructors/destructors

[Piotr Caban]

On 06/14/16 19:01, Iván Matellanes wrote:
> On 14/06/16 16:20, Piotr Caban wrote:
>> On 06/14/16 16:40, Iván Matellanes wrote:
>>>  /* ??_Dostream@@QAEXXZ */
>>> @@ -2287,23 +2341,48 @@ ostream* __thiscall ostream_assign(ostream
>>> *this, const ostream *rhs)
>>>  DEFINE_THISCALL_WRAPPER(ostream_vbase_dtor, 4)
>>>  void __thiscall ostream_vbase_dtor(ostream *this)
>>>  {
>>> -    FIXME("(%p) stub\n", this);
>>> +    ios *base = ostream_to_ios(this);
>>> +
>>> +    TRACE("(%p)\n", this);
>>> +
>>> +    ostream_dtor(base);
>>> +    ios_dtor(base);
>>>  }
>> The base should be computed using ostream_get_ios while calling ios_dtor:
>> TRACE("(%p)\n", this);
>> ostream_dtor(ostream_to_ios(this));
>> ios_dtor(ostream_get_ios(this));
> Do you mind explaining why is that required? I can't see the reason
ostream_vbase_dtor can be used to destroy object that has virtual base 
in any position pointer by vbtable. ostream_get_ios computes it using 
object's vbtable. You can easily see it by overwriting ostream->vbtable 
with garbage, the application will crash then on Windows.

On the other hand ostream_dtor is a virtual function that assumes "this" 
is at fixed offset from "base" that is passed to it. It's done this way 
because it has no access to vbtable. It's why you need to use 
ostream_to_ios in this case. There's no real need to call ostream_dtor 
here because it's an empty function (I don't know if it should be called 
here or if ostream_vbase_dtor should only destroy the vbase).

Thanks,
Piotr