Making RCSlice and DIP74 work with const and immutable
digitalmars-d at puremagic.com
Sun Mar 1 07:53:06 PST 2015
On Sunday, 1 March 2015 at 15:28:56 UTC, Jakob Ovrum wrote:
> On Sunday, 1 March 2015 at 01:40:40 UTC, Andrei Alexandrescu
>> We have a few candidates for solutions, but wanted to open
>> with a good discussion first. So, how do you envision a way to
>> define and access mutable metadata for objects (including
>> immutable ones)?
> I don't think const or immutable intrusive-reference-counted
> classes is a feasible idea.
> I understand the motivation: we want to dynamically allocate a
> class instance, initialize it and never mutate it again, and
> pass it around freely; *without* using tracing GC. Having it
> typed as immutable helps code readability and whatnot.
> 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
Argh! I didn't think about this. Any chance we can deprecate this
behaviour? It's also an obstacle for the implementation of
> There might be other problems, such as problems regarding ROM.
Not if the RC wrapper allocated the memory in the first place. It
knows that it can't be in ROM.
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