What is internal error E5912

Question

I ask a question here How to create simple XML in OmniXML and I get an answer from Gavin Watkinson.

I create the unit:

interface

uses
 OmniXML, OmniXMLProperties;

type
 TRow = class(TGpXMLData)
 public
  constructor Create(Node: IXMLNode); override;

  property Id: integer index 0 read GetXMLPropInt write SetXMLPropInt;
  property Name: WideString index 1 read GetXMLPropWide write SetXMLPropWide;
  property Surname: WideString index 2 read GetXMLPropWide write SetXMLPropWide;
  property Time: WideString index 3 read GetXMLPropWide write SetXMLPropWide;
  property Old: WideString index 4 read GetXMLPropWide write SetXMLPropWide;
  property Subject: WideString index 5 read GetXMLPropWide write SetXMLPropWide;
end;

TRows = class(TGpXMLList)
protected
  function GetRow(Value: integer): TRow;
public
  constructor Create(ParentNode: IXMLNode); reintroduce;

  function Add: TRow; reintroduce;

  property Rows[Value: integer]: TRow read GetRow; default;
end;

TRootsXml = class(TGpXmlDocList)
private
  fRows: TRows;
public
  constructor Create; reintroduce;
  destructor Destroy; override;

  property Ver: WideString index 0 read GetXMLAttrPropWide write SetXMLAttrPropWide;
  property RootFile: WideString index 1 read GetXMLAttrPropWide write SetXMLAttrPropWide;

  property Rows: TRows read fRows;
end;

implementation

constructor TRow.Create(Node: IXMLNode);
begin
  inherited;

  InitChildNodes(['id', 'name', 'surname', 'time', 'old', 'subjects'], 
                 ['', '', '', '', '', '']);
end;

constructor TRows.Create(parentNode: IXMLNode);
begin
  inherited Create(parentNode, '', 'row', TRow);
end;

function TRows.Add: TRow;
begin
  Result := TRow(inherited Add);
end;

function TRows.GetRow(Value: Integer): TRow;
begin
  Result := TRow(inherited Items[Value]);
end;

constructor TRootsXml.Create;
var
  xmlPI: IXMLProcessingInstruction;
begin
  inherited Create('Root', '', '', nil);

  xmlPI := XMLDoc.CreateProcessingInstruction('xml', 'version="1.0" encoding="utf-8"');
  XMLDoc.InsertBefore(xmlPI, node);

  InitChildNodes(['ver', 'file'], ['', '']);

  fRows := TRows.Create(node);
end; 

destructor TRootsXml.Destroy;
begin
  fRows.free;

  inherited;
end;

When I try to TRootsXml.ver = 'sat123'; and try to compile I get this error. 'Internal error E5912' and not compiling... But I can build without problem and run it.

So what is wrong and what is internal error E5912?

Answer 1

Internal errors are, well, internal errors in the compiler or linker. This time, it looks like the compiler. The number is merely an indication to the people who actually wrote the compiler. What it means is not documented and it is something that should actually never happen, in other words, it is a bug in the compiler. If it happens, you can only guess where or why it happens and try to modify your code until it disappears. That is not easy, and can be frustrating, but it is the only thing you can do.

I assume it is related to the fact that the code uses indexed properties with getters and setters defined in an ancestor class. I guess you could write your own getters and setters and call the inherited getters with the given index. Try this:

  TRootsXml = class(TGpXmlDocList)
  private
    fRows: TRows;
    function GetVer: WideString;
    procedure SetVer(const Value: WideString);
    function GetRootFile ... etc.. 
  public
    constructor Create; reintroduce;
    destructor Destroy; override;

    property Ver: WideString read GetVer write SetVer;
    property RootFile: WideString read GetRootFile write SetRootFile;
    property Rows: TRows read fRows;
  end;

function TRootsXml.GetVer: WideString;
begin
  Result := GetXMLAttrPropWide(0);
end;

procedure TRootsXml.SetVer(const Value: WideString);
begin
  SetXMLAttrPropWide(0, Value);
end;

// etc... similar code for GetRootFile and SetRootFile, but with index 1.

Not sure if that works, as I don't have Delphi 7 installed anymore, but please try it and report what happened.

I guess the original code was meant to be used in a higher version. That does not explain the internal error (as I said, these are bugs in the compiler), but it explains why it doesn't compile as expected, since I assume the code was tested, but apparently not in Delphi 7.