This API is based around the unsound idea that a process can perform
checked virtual memory loads to prevent crashing. This depends on
OS-specific APIs that may be unavailable, disabled, or impossible due to
virtualization.

It also makes collecting stack traces ridiculously slow, which is a
problem for users of DebugAllocator - in other words, everybody, all the
time. It also makes strace go from being superbly clean to being awful.