RCArray is unsafe

Zach the Mystic via Digitalmars-d digitalmars-d at puremagic.com
Tue Mar 3 19:46:34 PST 2015

On Tuesday, 3 March 2015 at 21:37:20 UTC, Andrei Alexandrescu 
> On 3/3/15 12:35 PM, Zach the Mystic wrote:
>> Isn't allocating and collecting a freelist also overhead?
> No. I don't have time now for a proof of concept and it seems 
> everybody wants to hypothesize about code that doesn't exist 
> instead of writing code and then discussing it.


>> The unoptimized lowerings would be:
>> {
>>   auto tmp = myGlobal; // bump count
>>   impureFun(myGlobal);
>> }  // tmp destroyed, --count
>> {
>>   auto tmp2 = c; // bump count
>>   fun(c, c);
>> } // --count
>> The only addition is an optimization where the compiler elides 
>> the
>> assignments and calls the add/release cycles directly.
> Do you have something reviewable, or just your own past posts?

Just my own past posts. My suggestion is based on the compiler 
doing all the work. I don't know how it could be tested without 
hacking the compiler.

> For the time being I want to move forward with DIP25 and 
> deferred freeing.

That's fine. I like DIP25. It's a start towards stronger safety 
guarantees. While I'm pretty sure the runtime costs of my 
proposal are lower than yours, they do require compiler hacking, 
which means they can wait.

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