Note 62: This low-level checks are used also by my Memory Snap utility, mentioned in the respective section of chapter 11.

The most relevant of this "low-level checks" covered at page 152 is the following empirical test for determining whether a point is actually a reference to an object (yes, the code is quite cryptic... there is a limited description in the book, of course). If you can come up with a better / more robust solution, I'll be interested...

      
function IsPointerToObject (Address: Pointer): Boolean;
var
  classPointer, vmtPointer: PChar;
  instsize: Integer;
begin
  Result := False;
  if (FindHInstance (Address) > 0) then
  begin
    vmtpointer := pchar(Address^);
    classpointer := vmtpointer + vmtSelfPtr;
    if Assigned (vmtpointer) and
      (FindHInstance (vmtpointer) > 0) then
    begin
      instsize := (Pinteger(
      vmtpointer + vmtInstanceSize))^;
      // check self pointer and "reasonable" instance size
      if (pointer(pointer(classpointer)^) =
           pointer(vmtpointer)) and
          (instsize > 0) and (instsize < 10000) then
        Result := True;
    end;
  end;
end;

This blog post is part of my "113 Delphi 2007 Handbook Notes" blogging project, to promote my new Delphi book.