Using C DLLs

Posted on 1997-05-18
Last Modified: 2010-04-04
I now beleive thet the problem i described accured
because i made a 32bit DLL and tried to use it with DELPHI 1.0
which is 16 bit.

After making a 16 bit DLL, i keep getting , at run time, when
DELPHI is trying to LINK the DLL, a "can't find file" message.

The code looks like thet:

  function CreateDiffJpeg (a : Integer):Integer;
    { Private declarations }
    { Public declarations }


  Form1: TForm1;

  index : integer;


{$R *.DFM}
function CreateDiffJpeg ;  external 'diffjpeg.dll' index 1;

procedure TForm1.Button1Click(Sender: TObject);

     index := index +1;



Any idea ?
Question by:gur
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Expert Comment

ID: 1336433
You should post the relevent code, so we can see what you might me doing wrong.


Accepted Solution

GWalter earned 100 total points
ID: 1336434
In the Delphi Program link the dll-call like this:function ComInit (Handle: Integer): Integer; cdecl; extern "testdll.dll" index 12;
It is very import to supply the index, I couldnt manage to linka DLL with the Name. You can get the Index e.g. in B C++ 5.0by using IMPDEF. Now you can read the indexes in the .DEF file.! Indexes may change when recompiling the program.* cdecl =>  C-Stack-Handling

In the C++- DLL:
Declaration as folowing:
#ifdef __WIN32_DLL__
  #define exp __declspec(dllexport)
  #define exp __declspec(dllimport)

int exp ComInit (int Handle);

(tried in MC C++ 4.0 , should also work with Borland C)

There might appear problems, when you link a DLL thats links another DLL, the DLL might be loaded twice.Gregor


Author Comment

ID: 1336435
Edited text of question

Author Comment

ID: 1336436
Edited text of question

Author Comment

ID: 1336437
I am sorry, but the problem was in the C DLL :
It seems thet there must be two functions (except my regular code) : the WEP exit function (in 16 bit DLL) and an EntryPoint function.


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