Invalid typecast: convert record to tobject on 64-bit platform

问题

it works on 32-bit platform.but not 64-bit here is the exzample

  TVerbInfo = packed record
    Verb: Smallint;
    Flags: Word;
  end;

var
  VerbInfo: TVerbInfo;
  strList : TStringList;
  verb : Smallint;
  flags : Word;
begin
  strList := TStringList.create();
  .....
  verbInfo.verb := verb;
  verbInfo.flags := flags;
  strList.addObject('verb1',TObject(VerbInfo));  //invalid typecast happened here
end;

can anyone help me? thank you very much

回答1:

You can try something like this:

function MakeVerbInfoObject(const AVerbInfo: TVerbInfo): TObject;
begin
  Result := nil;
  Move(AVerbInfo, Result, SizeOf(AVerbInfo));
end;

strList.addObject('verb1', MakeVerbInfoObject(VerbInfo));

回答2:

Your cast TObject(VerbInfo) will compile provided that SizeOf(TObject) = SizeOf(TVerbInfo). But TObject is a pointer and so its size varies with architecture. On the other hand, SizeOf(TVerbInfo) does not vary with architecture. Hence the cast can only work on one architecture.

Using casts like this is how you had to do things in pre-generics Delphi. But nowadays, you should be using generic containers.

For instance, if you have a list and the strings are unique then you can use a dictionary:

TDictionary<string, TVerbInfo>

If it is possible for there to be duplicate strings then you would need a new record declaration:

type
  TVerbInfo = record
    Name: string
    Verb: Integer;
    Flags: Word;
  end;

And then store a list of these in

TList<TVerbInfo>

One final point is that you should avoid using packed records. These result in mis-aligned data structures and that in turn leads to poor performance.

回答3:

I think you have to run this on different platforms and compare results

ShowMessage( IntToStr( SizeOf( Integer ) ) );
ShowMessage( IntToStr( SizeOf( Pointer ) ) );
ShowMessage( IntToStr( SizeOf( TVerbInfo ) ) );
ShowMessage( IntToStr( SizeOf( TObject ) ) );

I suspect you cannot do a hardcast, because the sizes differ.

You may try to use workarounds like

type TBoth = record
  case byte of
    0: ( rec: TVerbInfo);
    1: ( obj: TObject);
  end;

You can also try to use TDictionary<String, TVerbInfo> type instead of TStringList

来源：https://stackoverflow.com/questions/20680183/invalid-typecast-convert-record-to-tobject-on-64-bit-platform

标签

Delphi

casting

64-bit

record

tobject