Hash consing is a 1970s Lisp technique for supporting this that was recently rediscovered as "string interning": https://en.wikipedia.org/wiki/Hash_consing http

Hash consing is a 1970s Lisp technique for supporting this that was recently rediscovered as "string interning": https://en.wikipedia.org/wiki/Hash_consing https://en.wikipedia.org/wiki/Hash_consing In general copy-on-write schemes would be useful for this, and some persistent data structures can be as well. JonL White wrote a paper about this idea in 1980: http://3e8.org/pub/scheme/doc/lisp-pointers/v1i3/p17-white.pdf http://3e8.org/pub/scheme/doc/lisp-pointers/v1i3/p17-white.p... (favorite quote: "GC Once a Year: Enough?") Rivest and Shamir wrote an interesting paper on write once memory in 1982 that I feel might have some non-obvious applications to this: https://people.csail.mit.edu/rivest/RivestShamir-HowToReuseAWriteOnceMemory.pdf https://people.csail.mit.edu/rivest/RivestShamir-HowToReuseA... Linear types (http://home.pipeline.com/~hbaker1/LinearLisp.html http://home.pipeline.com/~hbaker1/LinearLisp.html) is a closely related idea in terms of avoiding garbage collection that has very useful concurrency properties. Most time-of-check-to-time-of-use and kernel/userspace race conditions would be prevented by using linear types for system call arguments. IMO linear types have enough benefits outside of memory management to make the trade-off of using them worth it vs the other techniques mentioned above.