On the other hand, not using atomics in heavy multithreaded code is just a recipe for disaster. The problem with shared_ptr is the fact that it uses atomics even in single-threaded code, which is obviously an overkill.

> The problem with shared_ptr is the fact that it uses atomics even in single-threaded code, which is obviously an overkill.

On the other hand imagine the security issues if shared_ptr was not thread-safe - you could just not reliably destroy a shared_ptr in any thread.

If you really know that you're going to get a graph of shared_ptr that do not move of a single thread, you can use boost::local_shared_ptr explicitely.

One of the advantages of rust is its ability to segregate safe-to-share (between concurrent contexts) and not so, at compile time.

While it can’t (yet?) be generic over them, it lets you use the non-atomic Rc in thread-bound structures and know this is never going to be shared between threads, whereas the more expensive Arc can have handles be moved from one thread to an other.

Counterparts for Rc [1] and Arc [2] (and compiler enforcement of their safe use [3]) are available in C++, though not standard.

[1] https://github.com/duneroadrunner/SaferCPlusPlus#reference-c...

[2] https://github.com/duneroadrunner/SaferCPlusPlus#tasyncshare...

[3] https://github.com/duneroadrunner/scpptool