Go Premium for a chance to win a PS4. Enter to Win

x
?
Solved

Problem with DLL parameters

Posted on 2004-04-25
4
Medium Priority
?
260 Views
Last Modified: 2012-05-04
Hello experts,

I am having some difficulty making a call to a dll function that I wrote.  I am passing a PChar parameter from my application to the DLL function (to avoid passing strings), but the value is corrupted when it is received by the dll.  This is a snapshot of my code:

**********************
Application code....

...

  try
    Handle := LoadLibrary(test.dll');
    @Func1:= GetProcAddress(Handle, Func1);
    if @Func1= nil then
      exit;
    Func1('Parameter');
  except
  end

...

**********************
DLL code....

...

function Func1(lpszCmdLine :PChar) : Integer; stdcall;
begin
  ShowMessage(Parameter: ' + lpszCmdLine);
end;

...


Am I doing something wrong?
Thanks,

dannyguindi
0
Comment
Question by:dannyguindi
  • 2
4 Comments
 
LVL 17

Accepted Solution

by:
geobul earned 200 total points
ID: 10915569
Hi,

1. What's your function declaration in the app? It should be something like:

type
   TFunc1 = function(lpszCmdLine :PChar) : Integer; stdcall;

var
  Func1: TFunc1;

or:
var
  Func1: function(lpszCmdLine :PChar) : Integer; stdcall;

2. Do not forget to free the library

 try
    Handle := LoadLibrary('test.dll'); // // there should be one more ' character
    if Handle <> 0 then begin
      @Func1:= GetProcAddress(Handle, 'Func1'); // two more ' chars
      if @Func1 <> nil then begin
        Func1('Parameter');
      end;
      FreeLibrary(Handle);
    end;
  except
  end
...

3. In the DLL:

function Func1(lpszCmdLine :PChar) : Integer; stdcall;
begin
  result := 0;
  ShowMessage('Parameter: ' + lpszCmdLine); // there should be one ' before Parameter
end;

Regards, Geo
0
 
LVL 19

Expert Comment

by:Melih SARICA
ID: 10915715
Sometimes, I dont even understand why, Pchar sucks... I always prefer PAnsiChar in this type of parameter  values..

0
 

Author Comment

by:dannyguindi
ID: 10918196
The missing ' were just typos in my snapshot.   What was causing the problem was the missing 'stdcall' in my function declaration.  It works now!

Thanks geobul.
0
 
LVL 17

Expert Comment

by:geobul
ID: 10918411
You are welcome :-)
0

Featured Post

Free Tool: Subnet Calculator

The subnet calculator helps you design networks by taking an IP address and network mask and returning information such as network, broadcast address, and host range.

One of a set of tools we're offering as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Hello everybody This Article will show you how to validate number with TEdit control, What's the TEdit control? TEdit is a standard Windows edit control on a form, it allows to user to write, read and copy/paste single line of text. Usua…
Introduction Raise your hands if you were as upset with FireMonkey as I was when I discovered that there was no TListview.  I use TListView in almost all of my applications I've written, and I was not going to compromise by resorting to TStringGrid…
Exchange organizations may use the Journaling Agent of the Transport Service to archive messages going through Exchange. However, if the Transport Service is integrated with some email content management application (such as an anti-spam), the admin…
Look below the covers at a subform control , and the form that is inside it. Explore properties and see how easy it is to aggregate, get statistics, and synchronize results for your data. A Microsoft Access subform is used to show relevant calcul…

916 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question