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FixInsight vs RTL

In this post I will continue to analyze Delphi source code. Last episode was about Delphi VCL, in this post we will look into Delphi RTL. I will ignore minor issues and will try to find out the most interesting pieces of code. All code examples in this post are related to Delphi XE7 (version 21.0.17017.3725).

W503 Assignment right hand side is equal to its left hand side

  constructor TNativeDownloader.Create(PublicKey: string; Salt: array of Byte; MainFile, PatchFile: TApkFileInfo);
  begin
    FMainFile := MainFile;
    FPatchFile := FPatchFile;
    FDownloader := TJNativeDownloaderLauncher.JavaClass.init(StringToJString(PublicKey), ByteArrayToJArray(Salt),
      CreateApkList(MainFile, PatchFile));
    Create;
  end;

I think, it should be “FPatchFile := PatchFile”.

W501 Empty EXCEPT block

  try
    Assert(FConnections.Count = 0); // All connections should have been removed
  except
  end;

That’s not an issue, just a WTF moment :)

W517 Variable hides a class field, method or property

procedure TTask.ExecuteReplicates(Root: TTask);
var
                                     
//  ReplicasQuitting: Boolean;
  ReplicaProc: TProc;
begin
//  ReplicasQuitting := False;
  ReplicaProc := procedure
    var
      CurrentTask, ChildTask: ITask;
    begin
      CurrentTask := CurrentTask;
      if not Root.ShouldCreateReplica {or ReplicasQuitting} then
        Exit;
      ChildTask := Root.CreateReplicaTask(ReplicaProc, Self, [TCreateFlag.Replicating, TCreateFlag.Replica]);
      ChildTask.Start;
      try
        Root.CallUserCode;
      except
        Root.HandleException(TTask(ChildTask), TObject(AcquireExceptionObject));
      end;
    end;
  ReplicaProc;
end;

W517 is a very popular warning for Delphi VCL and RTL. But I find this one to be the most interesting. TTask class has a class method called CurrentTask and CurrentTask variable hides that method. By the way there is one more warning (line 1865): “W503 Assignment right hand side is equal to its left hand side”.

So should that assignment look like “CurrentTask := Self.CurrentTask” or is it just a useless variable? In any case that code looks weird.

I cannot quote all W517 warnings, there are too many of them. But let me quote one more example from VCL.

procedure TCustomTaskDialog.ShowHelpException(E: Exception);
var
  Msg: string;
  Flags: Integer;
  SubE: Exception;
begin
  Flags := MB_OK or MB_ICONSTOP;
  if Application.UseRightToLeftReading then
    Flags := Flags or MB_RTLREADING;
  // ... [skipped]

That’s not a bug. But it could cause bugs in the future if you change this code. For instance, this code will compile even if you remove Flags variable, because TCustomTaskDialog has a property with the same name – Flags. Also it’s too easy to mistype and use the variable in this method instead of the propety and vice versa.

W504 Missing INHERITED call in destructor

destructor TJavaImport.Destroy;
begin
  TJNIResolver.DeleteGlobalRef(GetObjectID);
end;

There are a number of missed “inherited” calls again, I quote only one though.

W508 Variable is assigned twice successively

      // Another thread could start traversing the list between when we set the
      // head to P and when we assign to P.Next.  Initializing P.Next to point
      // to itself will make others spin until we assign the tail to P.Next.
      P.Next := P;
      P.Next := PThreadInfo(AtomicExchange(Pointer(FHashTable[H]), Pointer(P)));

Not an issue, as far as I understood. But I think it worth quoting. I never thought that it is possible to do multithreading like this.

That’s all I have to bring today. If you like this post, please let me know what library or framework you wish to run FixInsight against at the next time. FMX? JEDI? Anything else?