RelocationHolder constructors have bugs

RelocationHolder has a _relocbuf member, which is really just storage for a Relocation object. The constructors for RelocationHolder are both problematic. The no-arg constructor is

RelocationHolder::RelocationHolder() {
  new(*this) Relocation();
}

This is all very contorted and fragile. I wonder why RelocationHolder doesn't just use placement new to (default) construct the Relocation object. e.g.

new (_relocbuf) Relocation();

The other constructor is

RelocationHolder::RelocationHolder(Relocation* r) {
  // wordwise copy from r (ok if it copies garbage after r)
  for (int i = 0; i < _relocbuf_size; i++) {
    _relocbuf[i] = ((void**)r)[i];
  }
}

and that comment is just wrong, since the actual object could have been allocated close to the end of accessible memory, with a read beyond its real end potentially resulting in some kind of memory fault.