Eliminate class allocators and deallocators?

Don nospam at nospam.com
Thu Oct 8 05:58:08 PDT 2009


Steven Schveighoffer wrote:
> On Thu, 08 Oct 2009 07:26:37 -0400, Denis Koroskin <2korden at gmail.com> 
> wrote:
> 
>> On Thu, 08 Oct 2009 14:48:19 +0400, Steven Schveighoffer 
>> <schveiguy at yahoo.com> wrote:
>>
>>> On Wed, 07 Oct 2009 17:54:35 -0400, Denis Koroskin 
>>> <2korden at gmail.com> wrote:
>>>
>>>> On Wed, 07 Oct 2009 23:00:06 +0400, Sean Kelly 
>>>> <sean at invisibleduck.org> wrote:
>>>>
>>>>> auto x = cast(MyClass) malloc(MyClass.classinfo.init.length);
>>>>
>>>> I would expect a dynamic cast to occur at this line. Which will 
>>>> either result in an access violation (since you are trying to cast a 
>>>> garbage to an object) or result in a null being returned.
>>>
>>> malloc returns void *, so no dynamic cast.
>>>
>>> -Steve
>>
>> I know malloc returns void*. I didn't know you can hijack type system 
>> that easily.
>>
>> But then, if no dynamic cast takes place why cast(Object)cast(void*)0 
>> cannot be evaluated at compile time?
> 
> Your message made me test it :)
> 
> import std.stdio;
> 
> void *foo()
> {
>     return cast(void*)0;
> }
> 
> void main()
> {
>     auto o = cast(Object)foo();
>     writefln("here!");
>     o.opEquals(o);
> }
> 
> outputs:
> 
> here!
> Segmentation fault
> 
> So, no dynamic cast (dynamic cast would have looked at the classinfo of 
> null, segfaulting before the output).
> 
> So I would say, the fact that compile time evaluation doesn't work is a 
> bug maybe?
> 
> -Steve

CTFE is not yet supported for classes.



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