load dll
lazarus / 9-Editor

----------------------------------------------------------------------
skaner1900 · 2010-10-23 18:46

procedure TForm1.Button1Click(Sender: TObject);
var
  DLL : THandle;
  ShowForm : procedure;
begin
  DLL := LoadLibrary('LibSample.dll');
  try
    ShowForm := GetProcAddress(DLL, 'ShowForm');       <-------LINE 60
    if ShowForm=nil then raise Exception.Create('Bład');
    ShowForm;
  finally
    FreeLibrary(DLL);
  end;
end;

unit1.pas(60,17) Error: Incompatible types: got "Pointer" expected
"<procedure variable type of procedure;Register>"

i'm stupid or my lazarus is broken? ;(

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Phil · 2010-10-23 19:11

Since GetProcAddress returns a pointer, ShowForm should be declared
Pointer.

Then to call ShowForm, you normally cast it to a function type that
matches (1) the library function's parameter signature and (2) the
function's calling convention.

See various FPC source packages for how this is done. For example, I
see the MySql package does this extensively.

Also, make sure Windows can find your DLL, per normal Windows library
loading assumptions. See Windows documentation for LoadLibrary. If in
doubt include path to DLL.

Thanks.

-Phil

----------------------------------------------------------------------
cdbc · 2010-10-24 04:52

Hi
In lieu of Phils comment, it would look something like this:

procedure TForm1.Button1Click(Sender: TObject);
var
  DLL : THandle;
  ShowForm : procedure(Sender: TObject); register; // presumably
begin
  DLL := LoadLibrary('LibSample.dll');
  try
    pointer(ShowForm) := GetProcAddress(DLL, 'ShowForm');      
<-------LINE 60
    if ShowForm=nil then raise Exception.Create('Bład');
    ShowForm(Sender);
  finally
    FreeLibrary(DLL);
  end;
end;

Beware untested code, just some hints...
hth - Regards Benny