Making RCSlice and DIP74 work with const and immutable

via Digitalmars-d digitalmars-d at
Sun Mar 1 09:25:30 PST 2015

On Sunday, 1 March 2015 at 17:03:46 UTC, ketmar wrote:
> On Sun, 01 Mar 2015 15:53:06 +0000, Marc Schütz wrote:
>>> However, AFAICS, it comes with a serious problem. Immutable 
>>> objects are
>>> freely passable between threads, so surely an immutable RC 
>>> object would
>>> need atomic counting just like a shared RC object, but unlike 
>>> shared,
>>> immutable does not necessarily express the intent of sharing 
>>> between
>>> threads; the immutable RC object could easily be counting 
>>> atomically
>>> for nothing.
>> Argh! I didn't think about this. Any chance we can deprecate 
>> this
>> behaviour? It's also an obstacle for the implementation of 
>> thread-local
>> heaps.
> but deprecating this is... illogical at best. immutable objects 
> are
> immutable, so why can't i pass 'em to any thread? do you mean 
> that i
> can't use `immutable string = "mystr";` in different threads 
> without
> copying anymore?

Don't know. It was more of a question than a recommendation. It 
might be impractical.

OTOH, I don't think it's illogical, because thread-locality and 
immutability are independent concepts. There can be shared 
mutable data (`shared`)  as well as thread-local immutable data. 
Hmm... that would be equivalent to `const`, no? But that's 
getting off-topic.

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