[niekb]

> isn't everything multi-threaded these days..

There are alternative ways to utilize a machine with multiple cores, e.g. by running one thread per CPU core, and not sharing state between those threads; in each such thread you then have single-thread "semantics".

[mwkaufma]

weak_ptr supports this -- it's only mt-safe if you specialize it with std::atomic

[vlovich123]

Last I checked weak_ptr is always atomic (ignoring weird attempted glibc magic when you don’t link against pthread)

[mwkaufma]

? https://en.cppreference.com/w/cpp/memory/weak_ptr/atomic2

[vlovich123]

Oh sure, a single weak_ptr instance itself is not safe for multiple concurrent access of non-const methods. But weak_ptr -> shared_ptr reacquisition is atomic and all control block operations are:

> Note that the control block used by std::weak_ptr and std::shared_ptr is thread-safe: different non-atomic std::weak_ptr objects can be accessed using mutable operations, such as operator= or reset, simultaneously by multiple threads, even when these instances are copies or otherwise share the same control block internally. The type T may be an incomplete type.

There’s no variant of shared_ptr / weak_ptr that is non atomic in the standard library AFAIK.