Posted on 1997-04-27
Last Modified: 2010-04-04
 I don't get right results when using C++ made DLL in Delphi1 project.
Below you can see the vital parts of the program I am using. I can
successfully load the 16 bit DLL and use it. The first DLL call

         wsResult := RscCreateOptions(pulOptionsHandle);

should have a parameter 'a pointer to the variable that receives the
handle of the options structure'. After call I show the handle value
and it is  f. ex. 0045870000. Doesn't seem to be any handle value.

The second Dll call

         wsResult := RscGetOption(ulOptionsHandle,

confirms it saying that Options Structure is corrupted!
Why doesn't this work? Is the a different pointer structure in C++
compared to Delphi? How I must declare the pointer I pass to the C++
DLL?. If someone can help me I would be veru grateful!
These are the definations and preparations in order to use the C++

type TRscCreateOptions = function(pulOptionsHandle: PLongint): Integer cdecl;
type TRscGetOption = function(ulOptionsHandle: LongInt;
                            pcOptionSelector: PChar;
                            pvValue: PChar): Integer cdecl;

      var RscCreateOptions: TRscCreateOptions;
      var RscGetOption: TRscGetOption;

      Var hRsc4d: THandle;

      Procedure LoadRsc4dDLL;           {Load dll & function pointers}
        Var FP: TFarProc;
          If hRsc4d >= 32 Then FreeLibrary (hRsc4d);
          hRsc4d := LoadLibrary ('Rscw.DLL');
          If hRsc4d < 32 Then Exit;
          FP := GetProcAddress (hRsc4d, 'RSCOC');
          RscCreateOptions := TRscCreateOptions (FP);
          if (FP = NIL) then
            ShowMessage('RSCW.dll, function RscCreateOptions not found');
           FP := GetProcAddress (hRsc4d, 'RSCOG');
          RscGetOption := TRscGetOption (FP);
          if (FP = NIL) then
            ShowMessage('RSCW.dll, function RscGetOption not found');


This is the Delphi unit where C++ DLL is called.

        ulOptionsHandle:      Longint;
        pulOptionsHandle:       PLongInt;
        const pcHostInetAddress: Pchar = 'HOST_INET_ADDRESS';
        pcOptionValue:    PChar;


      {$R *.DFM}

      procedure TForm1.BitBtn1Click(Sender: TObject);
         pulOptionsHandle := Addr(ulOptionsHandle);
         wsResult := RscCreateOptions(pulOptionsHandle);
         if wsResult = 0 then
           ShowMessage('RscCreateOptions OK ');
           wsLuku := IntToHex(wsArvo, 10);
           ShowMessage('Options,handle='+ wsLuku);
         else begin

   {If successfully Options structure created,test  if it is OK}

         wsResult := RscGetOption(ulOptionsHandle,
         if wsResult = 0 then
           ShowMessage('RscGetOption Ok , address= ' +
         else begin
Question by:maurik
  • 2

Expert Comment

ID: 1335756
Do you have the DLL export declarations? If so, post them and I'll have a look. I believe the problem lies either in calling conventions or parameter sizing, but it's hard to say exactly what without both C and Delphi declarations...




Author Comment

ID: 1335757
This is rsc.h C-hederfile for the functions in question. This are the original function reclarations and the delphi ones was already in my question.

#ifndef SHORT
#define SHORT             short     /* 16 bit signed integer,   prefix 'n' */

#ifndef USHORT
#define USHORT   unsigned short     /* 16 bit unsigned integer, prefix 'u' */

#ifndef LONG
#define LONG            long      /* 32 bit signed integer,   prefix 'l' */

#ifndef ULONG
#define ULONG  unsigned long      /* 32 bit unsigned integer, prefix 'ul'*/

#ifndef VOID
#define VOID            void      /* void or unknown type,    prefix 'v' */

#define RscCreateOptions        RSCOC
#define RscGetOption            RSCOG

USHORT  FTYPE RscCreateOptions      ( ULONG PTYPE  *ulOptionsHandle );

USHORT  FTYPE RscGetOption          ( ULONG         ulOptionsHandle
                                  , CHAR  PTYPE  *pcOptionSelector
                                  , VOID  PTYPE  *pvValue


Accepted Solution

sperling earned 100 total points
ID: 1335758
From the H/PAS files, I can find only one possible error.

Are you certain "cdecl" should be used? I'd try "pascal" instead. I'll know for sure if you've got the FTYPE declaration somewhere...

And, the handle seems very correct. A common way to create a handle, is to allocate some memory and then cast the pointer to a longint, which is used as the handle. The handle you get looks like this.




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