Why are references to elements owned by extracted nodes valid but not usable?

Question

cppreference says this about std::set nodes:

Pointers and references to the extracted element remain valid, but cannot be used while element is owned by a node handle: they become usable if the element is inserted into a container.

The same rule applies to all STL node-based containers.

Why did the standard make that decision?

It is especially disturbing to have a reference that is "valid but not usable". Does it occur in other circumstances?

Might be something to do with how they are mutable in a node handle but not in a container — Artyer, Mar 29 '23 at 21:50
Yes, I just answered my own question by linking that answer. — Meatboy 106, Mar 29 '23 at 21:59

score 0 · Answer 1 · answered Mar 29 '23 at 21:57

0

The related questions section lead me to that answer to the exact same question.

TL;DR: Introducing mutability and allowing the use of references at the same time would be a violation of the strict aliasing rule.

answered Mar 29 '23 at 21:57

Meatboy 106

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Why are references to elements owned by extracted nodes valid but not usable?

1 Answers1