To be fair, Rust code can link to (entirely unsafe) C/C++ code or even JIT-compiled code, in which case you also want some runtime guarantees to mitigate exploi

To be fair, Rust code can link to (entirely unsafe) C/C++ code or even JIT-compiled code, in which case you also want some runtime guarantees to mitigate exploits in case they happen. In such a case, I believe a clearing allocator (or a set of custom allocators) sounds like the way to go. There may be a performance penalty, but you will be certain that all instances are covered, not just Vec<_>. Alternatively, a typed allocator (I wanted to link to a paper on the topic, but I can't find it) can, for a very small price, perform reasonably good mitigation on such exploits.