Solved

Problem with DLL parameters

Posted on 2004-04-25
4
252 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 50 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

Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

Question has a verified solution.

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

In this tutorial I will show you how to use the Windows Speech API in Delphi. I will only cover basic functions such as text to speech and controlling the speed of the speech. SAPI Installation First you need to install the SAPI type library, th…
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…
I designed this idea while studying technology in the classroom.  This is a semester long project.  Students are asked to take photographs on a specific topic which they find meaningful, it can be a place or situation such as travel or homelessness.…
Delivering innovative fully-managed cloud services for mission-critical applications requires expertise in multiple areas plus vision and commitment. Meet a few of the people behind the quality services of Concerto.

932 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

Need Help in Real-Time?

Connect with top rated Experts

12 Experts available now in Live!

Get 1:1 Help Now