[dj-wonk]

Well said. There are many kinds of behavior that may be considered "out of specification" or not adhering to a contract. Here are just four:

* https://en.wikipedia.org/wiki/Undefined_behavior

* https://en.wikipedia.org/wiki/Timing_attack

* https://en.wikipedia.org/wiki/Thread_safety

* https://en.wikipedia.org/wiki/Privilege_escalation

Some of these probably don't come to everyone's minds right away. Please share your favorites.

The behavior(s) that a particular language guarantees is a design question. Once those guarantees are specified, we can objectively evaluate a particular language in terms of how well it does according to its own standards.