anchor.diff:    err: bson_error_t;
     query: IBson;
   begin
  +  FillChar(err, SizeOf(bson_error_t), 0);
     if AQuery = nil then
       query := NewBson
     else
  
positive.code:   nativeFile: Pointer;
    err: bson_error_t;
  begin
    nativeFile := mongoc_gridfs_find_one_cnv_by_filename(FNativeGridfs,
                                                         PAnsiChar(AName),
                                                         @err, FlagsToNative(AFlags));
    if nativeFile = nil then
      raise EMongoGridfs.Create(@err);
  
    Result := NewMongoGridfsFile(nativeFile);
  end;
  
negative.code:     FNativeGridfs: Pointer;
      FError: bson_error_t;
      function FlagsToNative(AFlags: TMongoFlags): Integer;
      procedure RaiseFindFileError(err: bson_error_p);
    public
      constructor Create(ANativeGridfs: Pointer);
      destructor Destroy; override;
  