GC.malloc is pure - wat

[deadalnix via Digitalmars-d]

On Friday, 1 April 2016 at 01:19:01 UTC, Timon Gehr wrote:
> On 01.04.2016 00:52, deadalnix wrote:
>>
>>
>> DMD optimizes malloc because the only reason it would have to 
>> return a
>> different pointer would be internal state (and in fact, it 
>> indeed has
>> internal state).
>
> It's the other way around. Without the "optimization" there is 
> no way for a 'pure' function to return a reference to the same 
> mutable memory block independent of its arguments more than 
> once. In the end it is up to the spec, but IMO compiler 
> optimizations should not be able to introduce mutable aliasing 
> that was not there before. (Even for immutable references, 
> sharing the same result is moot, as D supports checking for 
> reference equality.)

I can see the logic. Yet, the only thing that can be returned if 
no state is exposed is either a constant or something computed 
from 1 (cast(void*) 1).

But yeah, the optimization should probably not be done if the 
return type is mutable.