How to crash Delphi compiler in four easy steps

Step one

Start Delphi XE.

Step Two

Create simple project.

program F2048;

uses
  Classes,
  StreamEnh;

type
  TTest = class(TStream)
  end;

begin
end.

Step Three

Create unit StreamEnh.

unit StreamEnh;
                                 
interface

uses
  SysUtils,
  Classes;

type
  TGpStreamEnhancer = class helper for TStream
  public
    procedure BE_WriteDWord(const dw: cardinal);
    procedure BE_WriteHuge(const h: Int64);
  end;

implementation

procedure TGpStreamEnhancer.BE_WriteDWord(const dw: cardinal);
begin
end;

procedure TGpStreamEnhancer.BE_WriteHuge(const h: Int64);
begin
  BE_WriteDWord(Int64Rec(h).Hi);
  BE_WriteDWord(Int64Rec(h).Lo);
end;

end.

Step Four

Rebuild.

Expected: Program should compile.

Reality: [DCC Fatal Error] F2048.dpr(1): F2084 Internal Error: C10343

Funny things happen if you don’t restart the Delphi. Try recompiling: [DCC Fatal Error] F2048.dpr(9): F2084 Internal Error: O826

Workaround

Change BE_WriteHuge to use a temporary variable:

procedure TGpStreamEnhancer.BE_WriteHuge(const h: Int64);
var
  a: int64;
begin
  a := h;
  BE_WriteDWord(Int64Rec(a).Hi);
  BE_WriteDWord(Int64Rec(a).Lo);
end;

Be aware though that you have to restart Delphi if you want the fixed code to compile. Otherwise you’ll be getting Internal error O826.

QC

Reported as QC #91327. Vote for it!