Fiber implementation questions

[Dicebot via Digitalmars-d]

On Tuesday, 21 June 2016 at 12:18:37 UTC, Steven Schveighoffer 
wrote:
> On 6/21/16 6:14 AM, Dicebot wrote:
>> On 06/20/2016 11:17 PM, deadalnix wrote:
>>>> Q2: core.thread.Fiber implementation looks like GC does not 
>>>> scan
>>>> function stacks for yielded contexts. Why?
>>>>
>>>
>>> Doesn't it ?
>>
>> https://github.com/dlang/druntime/blob/master/src/core/thread.d#L4328
>> allocates fiber stack using mmap / malloc / VirtualAlloc and 
>> doesn't
>> seem to register that memory in GC. But that may be indirect 
>> result of
>> https://github.com/dlang/druntime/blob/master/src/core/thread.d#L4439
>> call, which is why I am not sure.
>
> It appears that Fibers interact with the GC differently:
>
> https://github.com/dlang/druntime/blob/master/src/core/thread.d#L1611
>
> -Steve

I suspected something like this, it explains a lot. Do you know 
why this approach was chosen instead of simply registering 
allocated memory for GC scan? Does GC has special approach for 
stack scanning which differs from normal memory?