Destroying structs without a typeinfo object

[Benjamin Thaut]

Am 04.05.2012 15:14, schrieb Steven Schveighoffer:
> On Fri, 04 May 2012 08:38:21 -0400, Benjamin Thaut
> <code at benjamin-thaut.de> wrote:
>
>> Am 04.05.2012 14:18, schrieb Steven Schveighoffer:
>>> On Fri, 04 May 2012 02:45:03 -0400, Benjamin Thaut
>>> <code at benjamin-thaut.de> wrote:
>>>
>>>> Hi,
>>>>
>>>> I'm currently doing some manual memory management and as the delete
>>>> keyword is deperecated I want to replace it with a custom Delete
>>>> template. I now need to destroy a array of structs, this however seems
>>>> only be possible by using the typeinfo object of the struct and
>>>> calling xdtor on that which is a indirect function call for every
>>>> struct in the array. I would like to destroy the struct directly with
>>>> a direct call to the destructor. This seems not to be possible because
>>>> calling __dtor results in calling the wrong dtor (apperently there are
>>>> 3, __dtor, __fieldDtor, __aggrDtor). So __dtor is the wrong destructor
>>>> because it does not destroy any members of the struct but __fieldDtor
>>>> and __aggrDtor are not callable. They show up in the
>>>> __traits(allMembers) list but if you try to call them you get a error
>>>> message that such a property does not exist. So is there any way to
>>>> directly destroy a struct, and if not why can't we directly expose the
>>>> correct destructor, because apprently it is known at compile time.
>>>
>>> Look at what object.clear() does, since it is meant to replace delete.
>>>
>>> In fact, I'd advise just using that if you have the type handy.
>>>
>>> -Steve
>>
>> object.clear() useses the typeinfo.destroy() method which is a virtual
>> function call plus a indirect function call. So thats even one level
>> of indirection more. Also clear does reinitializle the struct after
>> destroying it, which is completely unneccesary in my case, because I'm
>> about to free the memory anyway.
>
> Look at what TypeInfo_Struct.destroy() does:
>
> override void destroy(void* p)
> {
> if (xdtor)
> (*xdtor)(p);
> }
>
> So here is what I'd suggest (for an array of struct S):
>
> auto ti = typeid(S).xdtor;
>
> if(xdtor)
> foreach(ref s; arr)
> (*xdtor)(&s);
>
> Which should be as efficient as possible, given the current
> implementation, you don't have to repeat the lookup for each element.
>
> I remember that __dtor does the wrong thing, and I advocated it should
> do the same thing as calling xdtor, but it didn't go anywhere.
>
> -Steve

Thanks, but thats exactly what I'm currently doing. This still is a 
indirect function call, and I hoped that there is a way to directly call 
the destructor.

Kind Regards
Benjamin Thaut