Escaping the Tyranny of the GC: std.rcstring, first blood

[Andrei Alexandrescu via Digitalmars-d]

On 9/15/14, 8:58 AM, Rainer Schuetze wrote:
>
>
> On 15.09.2014 07:49, Andrei Alexandrescu wrote:
>>> I haven't found a single lock, is single threading by design or is
>>> thread-safety on your todo?
>>
>> Currently shared strings are not addressed.
>
> Please also consider usage with const and immutable:
>
> * both will disallow changing the reference count without casting

I think these work fine. If not, please send examples.

> * immutable means implicitely shared between threads, so you'll have to
> make RCString thread-safe even if shared isn't explicitly supported.

Hmmm, good point. That's a bug. Immutable postblit and dtors should use 
atomic ops.

> Unfortunately, I've yet to see an efficient thread-safe implementation
> of reference counting (i.e. without locks).

No locks needed, just interlocked ++/--.

> VC used to have reference counted strings, but moved away from it. Maybe
> it doesn't pull its own weight in the face of the
> small-string-optimization.

The reason of C++ strings moving away from refcounting is not strongly 
related to interlocked refcounting being slow.


Andrei