Approaches to memory reclamation

In the discussion that follows, the three techniques are laid out roughly in order of their speed, slowest to fastest, as well as their difficulty, easiest to hardest. You should not be discouraged—you are now at one of the forefronts of the software engineering world. Welcome. Go boldly.

Reference counting

Reference-counting memory reclamation associates a piece of protected data with an atomic counter. Every thread reading or writing to that protected data increases the counter on acquisition and decreases the counter on de-acquisition. The thread to decrease the counter and find it as zero is the last to hold the data and may either mark the data as available for reclamation or deallocate it immediately. This should, hopefully, sound familiar. The Rust standard library ships with std::sync::Arc—discussed in Chapter 4, Sync and Send – the Foundation of Rust Concurrency, and Chapter 5, Locks – Mutex, Condvar, Barriers and RWLock, especially—to fulfill this...