Re: [Boost-users] shared_ptr questions

Subject: Re: [Boost-users] shared_ptr questions
From: John Dlugosz (JDlugosz_at_[hidden])
Date: 2009-08-18 11:21:22

> -----Original Message-----
> I think this might help:
> 
> http://www.boost.org/doc/libs/1_39_0/libs/smart_ptr/shared_ptr.htm#Thre
> adSafety
> 
> It covers shared_ptr only, though.
> 
> 
> Regards,
> 
> Roland

I had read that.  " A shared_ptr instance can be "read" (accessed using only const operations) simultaneously by multiple threads. Different shared_ptr  instances can be "written to" (accessed using mutable operations such as operator= or reset) simultaneosly by multiple threads (even when these instances are copies, and share the same reference count underneath.)"  was instructive.  That's what I need.

But I was specifically wondering about the mix of weak_ptr's.  I guess mine is more complicated because it can do lazy copy on write, but still the effect of making the unowned pointer getting ownership at the same time as other threads are releasing all the existing owners was an issue of specific importance.  I implemented a "sticky zero" non-blocking counter for the purpose.  

I want to make sure that the Boost implementation can do this robustly and efficiently, too.  And perhaps point out that weak_ptr's need thread issue documentation too.

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