Lape array bug trigger | Solved

program new;
(*
  There was no bug, we used move on an array without cleanup old reference.
*)

type
  TPathStruct = packed record pts: TPointArray; d: Double; end;
  TQueueHelper = record
    lo, hi: Int32;
    data: array of TPathStruct;
  end;

procedure TQueueHelper.Init(sz: Int32);
begin
  SetLength(Self.data, sz);

  Self.hi := -1;
  Self.lo := 0;
end;

function TQueueHelper.SearchClosest(value: Double): Int32;
var
  l, h: Int32;
begin
  l := Self.Lo;
  h := Self.Hi;

  while l <= h do
  begin
    Result := (l + h) div 2;
    if Self.Data[Result].d < value then
      h := Result - 1
    else if Self.Data[Result].d > value then
      l := Result + 1
    else
      Exit(Result);
  end;
end;

function TQueueHelper.Insert(path:TPointArray; distance: Double): Int32;
var
  idx: Int32;
begin
  idx := Self.SearchClosest(distance);
  if Self.Data[idx].d > distance then Inc(idx);

  if (self.hi+1-idx) > 0 then
  begin
    WriteLn('>>> move from: ', idx,' to ', idx+1,', bytes: ', (self.hi+1-idx)*(SizeOf(TPathStruct)));
    Move(Self.data[idx], Self.data[idx+1], (self.hi+1-idx)*(SizeOf(TPathStruct)));

    // -- EDIT 2025: ----------
    Move(blank, Self.data[idx], SizeOf(TPathStruct)); // it was this or update refcount

    // problem was that we duplicated an array without refcount update
    // ------------------------
  end;

  Self.data[idx].d   := distance;
  Self.data[idx].pts := path;

  Inc(Self.hi);
end;


procedure TQueueHelper.Pop(out path:TPointArray; out distance: Double);
begin
  path     := self.data[self.hi].pts;
  distance := self.data[self.hi].d;
  Dec(Self.Hi);
end;

function TQueueHelper.AsString(): String;
var
  tmp: array of TPathStruct;
begin
  tmp := self.data;
  SetLength(tmp, self.hi+1);
  Result := ToString(tmp);
end;



var
  q: TQueueHelper;
  p: tPointArray;
  d: Double;
begin
  q.Init(1000);

  q.Insert([[2,2]], 2);
  WriteLn q.AsString;

  q.Insert([[2,1], [2,2]], 4);
  WriteLn q.AsString;

  q.Insert([[2,2], [1,2]], 8);
  WriteLn q.AsString;

  q.Insert([[2,2], [3,2]], 16);
  WriteLn q.AsString;

  q.Insert([[2,2], [2,3]], 32);
  WriteLn q.AsString;

  q.Insert([[2,2], [2,3], [4,4]], 64);
  WriteLn q.AsString;
end.