Jeffrey Yasskin:
Porting lock-free data structures from Java is complicated by the fact that the implementations assume garbage collection. There are a few techniques available for dealing with manual memory management without locks, but they complicate the implementation of algorithms that are complex enough already. So I'm thinking about trying to implement an atomic_shared_ptr<T> along the lines of the interface for other atomics defined in http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2427.html but using shared_ptr<T> as a value type. The implementation I'm thinking of uses hazard pointers (http://erdani.org/publications/cuj-2004-12.pdf) and double-wide-cas (cmpxchg16b on x86-64). So I have three questions for this list:
1) Would there be interest in adding such a type to the Boost smart pointers?
I (and many others) will be very, very interested in your implementation, doubly so if you implement it using the interface proposed in http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2007/n2297.html#atomic I can't guarantee that your implementation will make it into Boost since hazard pointers are rumored to be patent-encumbered.
2) Has someone already done this?
If you google :-) for Joe Seigh's atomic_ptr, you'll find his implementation. It doesn't implement the entire shared_ptr interface though, so your implementation will be unique in this regard.