ASan is "Address Sanitizer". See https://github.com/google/sanitizers/wiki/AddressSanitizer

Arena, and by extension ResourceArea, are custom allocators. They allocate chunks of malloc-based memory and allocate objects in them, one after another. As far as ASan is concerned, the entire malloc-based chunk is valid until free. In reality the subregions of the chunks are not valid until handed out by the arena.

ASan supports user-specified poisoning/unpoisoning. This allows ASan to detect unexpected usage of memory, effectively allowing us to detect use-after-free in the Arena.

This enhancement will instrument Arena and ResouceArena for ASan using poisoning/unpoisoning.

Additionally JDK-8298445 will be able to make use of poisoning/unpoisoning information by not looking for pointers in poisoned memory. This makes it much more accurate and determenistic.