If we only store the biased pointer, the map ptr region will not
be recognized as reachable memory by leak checkers. This is
primarily problematic for fuzzing, because this is persistent
memory that may be reallocated during the request, without being
an actual leak.
Avoid this by simply storing both the real base pointer of the
allocation, as well as the biased base pointer used for accesses.
Nikita Popov
6434c93a27