Sorry for the belated response. Jeffrey Yasskin:
On Jan 18, 2008 10:34 AM, Peter Dimov <pdimov@pdimov.com> wrote: ...
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
Thanks for the support! I currently plan to extrapolate from the design of atomic<T> from N2427 instead of adding operations to shared_ptr itself. The requirement that "A program is allowed to access the same shared_ptr instance concurrently from multiple threads if the access is done exclusively via the member functions in this section." implies that instances accessed through those three methods are logically a separate type from instances accessed through other methods.
There are use cases in which you really do want to access the same variable in both atomic and non-atomic ways. Something like: rwm_.rdlock(); // use atomic accesses on px rwm_.unlock(); //... rwm_.wrlock(); // use non-atomic accesses on px, we're exclusive rwm_.unlock();