allocate array with new

[Ondrej Pokorny]

On Tuesday, 15 May 2012 at 12:36:30 UTC, Dmitry Olshansky wrote:
> On 15.05.2012 16:27, Ondrej Pokorny wrote:
>> On Tuesday, 15 May 2012 at 09:44:08 UTC, Jonathan M Davis 
>> wrote:
>>> On Tuesday, May 15, 2012 11:26:49 Namespace wrote:
>>>> On Tuesday, 15 May 2012 at 09:23:51 UTC, Kagamin wrote:
>>>> > Difference with what?
>>>> > new is a safe feature: it allocates in the GC heap
>>>>
>>>> That's what i mean. So i have to delete it yourself with 
>>>> "delete
>>>> arr;", or not?
>>>
>>> No. _Never_ use delete. It's going to be deprecated. The GC 
>>> worries about
>>> freeing memory allocated on the GC heap, and new always 
>>> allocates on
>>> the GC
>>> heap. If you don't want to allocate on the GC heap, then use 
>>> malloc
>>> and free,
>>> in which case you _do_ need worry about freeing the memory.
>>>
>>> If you need to force destruction before the GC collects an 
>>> object, you
>>> can
>>> call clear on that object to have its destructor called and 
>>> its vtbl
>>> zeroed
>>> out, but it's memory still isn't freed. That's the GC's job.
>>>
>>> If you really have to, you can use core.memory to manipulate 
>>> the GC heap
>>> (including calling GC.free), but you really shouldn't be 
>>> messing with
>>> any of
>>> that unless you really need to and you know what you're doing.
>>>
>>> - Jonathan M Davis
>>
>> Hi,
>> does this hold for structs too?
>>
>> struct H
>> {
>> this(int a){writeln("ctor");}
>> ~this(){writeln("dtor");}
>> };
>>
>> ...
>>
>> H* h = new H(5);
>> clear(h);
>> ...
>>
>> output:
>>
>> ctor
>>
>> seems like destructor is not called.
>>
>> if I change declaration of H to class H. output is following:
>>
>> ctor
>> dtor
>>
>> I tried to create object according to RAII idiom and in case 
>> of struct H
>> my file handle remained open and I was still able to write to 
>> file...
>>
>> Ondrej
>>
> I thought in C++ RAII is about (i.e. even in C++ no heap 
> allocation):
> H h = H(5);
>
> Same works in D. A call to clear  in you code above doesn't 
> call destructor, it only zeros out pointer.
> If you absolutely need pointers & heap and yet manual memory 
> managment use:
> clear(*h);
>
>
> Explanation:
> clear(x) calls x.__dtor if x is struct or class, then assigns
> x = T.init;
>
> A better way might be to just check if x.__dtor is callbale 
> (thus pointer to sstruct will also work).

I don't need this stuff I am playing with language and wonder
why. Originally I had there auto h = H(5); and after changing H
to struct I did not realized why that happened.

Thanks a lot for explanation, now it makes perfect sense, but I
have still little bit unpleasant felling about it because of
behavior of ref to classes vs pointers to structs with clear.
Both are dynamically allocated data, so I was expecting same
response from clear(x).

Ondrej