Creating a reference counted type?

[ZombineDev via Digitalmars-d-learn]

On Sunday, 12 June 2016 at 14:49:18 UTC, Gary Willoughby wrote:
> On Sunday, 12 June 2016 at 14:45:12 UTC, ketmar wrote:
>> ahem... wut?! we have one copy of our struct freed half the 
>> way, and another copy has refcount of 2, so it won't be freed 
>> at all. it doesn't so innocent as it looks: we may try to use 
>> `f` in `main`... just to find out that resources was 
>> mysteriously freed, and refcount is total garbage.
>
> Hmmm. I thought it looked *too* simple. Have you any idea if 
> there is a simple solution to this?

You need to allocate the ref count on the heap so it is actually 
shared between all copies of the struct. Also if you want to 
share the reference between multiple threads, you need to use 
core.atomic.atomicOp for incrementing and decrementing.

See std.typecons.RefCounteed's implementation for reference 
https://github.com/dlang/phobos/blob/v2.071.0/std/typecons.d#L4712

You can use AffixAllocator 
http://dlang.org/phobos-prerelease/std_experimental_allocator_building_blocks_affix_allocator.html, so that ref count is automatically placed before or after the actual objected that is being ref counted. Just note that AffixAllocator is safe to use only by a single thread.