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Subject: Re: [boost] [root_ptr] Deterministic Javascript-like memory manager
From: Phil Bouchard (philippeb8_at_[hidden])
Date: 2017-07-09 18:30:48

On 07/09/2017 11:01 AM, Phil Bouchard via Boost wrote:
> On 07/08/2017 10:39 PM, Phil Bouchard via Boost wrote:
>> That is flawless... If anybody is willing to fool this memory manager
>> then please go ahead!
> Actually I think I'll still need to fine tune-it but I'm getting there.
> Also it'll be better if I reintegrate the old "inclusive" mode (in the
> master branch) and the user can choose the mode at run-time or
> compile-time.

Little change here in the code:

--- include/boost/smart_ptr/root_ptr.hpp (revision 678)
+++ include/boost/smart_ptr/root_ptr.hpp (working copy)
@@ -314,7 +314,8 @@

                  // upscale the proxy of the operand
                  if (px_->depth() < p.px_->depth())
- propagate(p);
+ p.proxy(* px_);

                  base::operator = (p);

I'm pretty sure I got it right if I add the notion of 'upscaling the
scope of a variable'. For example:

int main()
     cout << "Scope 0: BEGIN" << endl;
         node_proxy x; // 1st proxy
         node_ptr<A> a1 = make_node<A>(x, x, "a1");

         cout << "Scope 1: BEGIN" << endl;
             node_proxy x; // 2nd proxy
             node_ptr<A> b1 = make_node<A>(x, x, "b1");
             node_ptr<A> b2 = make_node<A>(x, x, "b2");

             a1 = b1; // upscale scope of b1 to use 1st proxy

             b1 = make_node<A>(x, x, "b3"); // scope of b1 will still be
associated with the 1st proxy
             b1->i = b1; // cycle
         cout << "Scope 1: END" << endl;
     cout << "Scope 0: END" << endl;

Will output:

Scope 0: BEGIN
A::A(const boost::node_proxy&, const char*): a1
Scope 1: BEGIN
A::A(const boost::node_proxy&, const char*): b1
A::A(const boost::node_proxy&, const char*): b2
A::~A(): a1
A::A(const boost::node_proxy&, const char*): b3
A::~A(): b2
Scope 1: END
A::~A(): b1
A::~A(): b3
Scope 0: END

Now here b1 got "upscaled" because it was once associated with a
variable of a higher scope: a1 (closure in Javascript). And you can't
downscale a variable to a lower scope so b1 will get destroyed in scope 0.

Do you understand what I'm talking about?


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