Delphi XE2, Delphi 10 Seattle, Application Handle, Dll, Action Error

Question

I have App.exe applications created in Delphi XE2, then the DLL is created in Delphi 10 Seattle. When I pass an Application.Handle to a DLL after calling a DLL I get an error "Exception class .... 'floating point stack check ...'". When I remove the Application.Handle from EXE assignment, the DLL is ok. I noticed this is related to the TAction action that is hooked to controlek. Eg to MainMenu. I'll also add that when a DLL is called from an EXE that is written in Delphi 10 Seattle it's all ok.

Thank you for your help.

Below I attach some code

Code Delphi XE2

unit Form_MainApp;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes,
  Vcl.Graphics, Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Vcl.Buttons;

type
  TfrmMainApp = class(TForm)
    btnRunDLL: TBitBtn;
    procedure btnRunDLLClick(Sender: TObject);
  private
  public

  end;

var
  frmMainApp: TfrmMainApp;

implementation

{$R *.dfm}

procedure TfrmMainApp.btnRunDLLClick(Sender: TObject);
const
  LibraryFolder = '\Library\';
    DLLName = LibraryFolder + 'TestDLL.dll';
type
  TDLLProc = Function(pAppHandle:HWND; pAppTitle:PChar; pId:Integer; var pOUTId:Integer): TModalResult; StdCall;
var
  DLLHandle: THandle;
    DLLProc: TDLLProc;
  DLLResult: TModalResult;
  OUTId: Integer;
  LibraryName: String;
begin
  LibraryName:=ExtractFileDir(Application.ExeName) + DLLName;
  DLLHandle:=Winapi.Windows.LoadLibrary(PChar(LibraryName));
    try
    if DLLHandle <> 0 then
      begin
        @DLLProc:=Winapi.Windows.GetProcAddress(DLLHandle, PChar('Run_TestDLL'));
        if (@DLLProc <> nil) then
          DLLResult:=DLLProc(Application.Handle, PChar(Application.Title), 0, OUTId);
      end;
    finally
    if DLLHandle <> 0 then
      Winapi.Windows.FreeLibrary(DLLHandle);
    end;
end;

end.

Code Delphi 10 Seattle

library TestDLL;

  uses
  System.SysUtils,
  System.Classes,
  Controls,
  Forms,
  Dialogs,
  Windows,
  Form_MainDLL in 'Form_MainDLL.pas' {frmMainDLL};

{$R *.res}

Function Run_TestDLL(pAppHandle:HWND; pAppTitle:PChar; pId:Integer; var pOUTId:Integer):TModalResult; StdCall;
begin
  Application.Handle:=pAppHandle;
    Result:=mrNone;
  try
    frmMainDLL:=TfrmMainDLL.Create('Test');
    frmMainDLL.ShowModal;
  finally
    FreeAndNil(frmMainDLL);
      Result:=mrOk;
  end;
end;

exports
  Run_TestDLL;
begin
  ReportMemoryLeaksOnShutdown:=True;
  Randomize;
end.

FORM in DLL

unit Form_MainDLL;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants,
  System.Classes, Vcl.Graphics, Vcl.Controls, Vcl.Forms, Vcl.Dialogs,
  cxEdit, dxBar, Vcl.ExtCtrls, System.Actions,
  Vcl.ActnList, Vcl.Menus, Vcl.StdCtrls;

type
  TfrmMainDLL = class(TForm)
    mmMain: TMainMenu;
    mmEdit: TMenuItem;
    mmAdd: TMenuItem;
    mmData: TMenuItem;
    mmClose: TMenuItem;
    mmOpen: TMenuItem;
    btnSetAction: TButton;
    alMain: TActionList;
    acAdd: TAction;
    procedure acAddExecute(Sender: TObject);
    procedure btnSetActionClick(Sender: TObject);
  private
    fName: String;
  public
    constructor Create(pName:String);reintroduce; virtual;
    destructor Destroy; Override;
  end;

var
  frmMainDLL: TfrmMainDLL;

implementation

{$R *.dfm}

constructor TfrmMainDLL.Create(pName:String);
begin
  inherited Create(Nil);
  fName:=pName;
end;

destructor TfrmMainDLL.Destroy;
begin

  inherited;
end;

procedure TfrmMainDLL.acAddExecute(Sender: TObject);
begin
  ShowMessage('TEST');
end;

procedure TfrmMainDLL.btnSetActionClick(Sender: TObject);
begin
  mmAdd.Action:=acAdd;
  mmAdd.OnClick:=acAddExecute;
end;


end.

Answer 1

You need to ensure that messages CM_ACTIONEXECUTE and CM_ACTIONUPDATE will not be sent from VCL code in DLL to VCL code in EXE (because they have different runtime, and different TAction objects).

There are several ways:

1. Hook window procedure for TApplication.Handle window and filter messages. For example see HookApplication and UnhookApplication at: https://github.com/achechulin/loodsman/blob/master/Loodsman/Loodsman.Infrastructure.PluginUtils.pas
2. Add OnUpdate and OnExecute handlers to all TAction objects.
3. Do not use TAction at all.

Also, you need to catch all exceptions in Run_TestDLL.