We should write some tests to ensure that asan is working to check memory leaks, dangling pointers, and so on. I know that legacy/trac#25386 links asan, but I don't know if it actually checks stuff that we want checked. We should check that it checks what we want checked. I envision this looking like a `test_fragile_hardening.c` (or a series of such files) and some helper Rust code that does some bad behavior and a wrapper that ensures that it crashes. Landing this requires legacy/trac#25386, but writing it does not; just assume that Rust and C can arbitrarily call each other (with the proper boilerplate), and asan is supposed to catch everything that it catches in C.