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Problems importing functions from a DLL in a C++ program

Posted on 1998-10-29
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Last Modified: 2012-06-27
Hi all... I need your help again:

I've programmed the following DLL (I only show the function definitions):

#include <windows.h>
#include "handkey.h"
#pragma hdrstop

class TSerial
{
  public:
    BOOL      Error;
    MSG_FMT      MessageOut, MessageIn;

    TSerial( );                    // Constructor
    ~TSerial( );           // Destructor
    void SendMessage( );     // Envía un mensaje
    void ReceiveMessage( );  // Recibe el mensaje

  private:
    HANDLE      hCom;
    LPSTR      Message;
};

BOOL APIENTRY DllEntryPoint( HINSTANCE hDLL, DWORD dwReason, LPVOID Reserved )
{
  hInstance = hDLL;
  switch( dwReason )
  {
       case DLL_PROCESS_ATTACH:
       {
            break;
       }
       case DLL_PROCESS_DETACH:
       {
            break;
       }
  }
  return TRUE;
}

BOOL APIENTRY Setup( )
{
  ..................
}

TSerial::TSerial( )
{
  ................................
}

TSerial::~TSerial( )
{
  ............................
}

void TSerial::SendMessage( )
{
  ................................
}

void TSerial::ReceiveMessage( )
{
  .............................
}

BOOL APIENTRY HandKey_RequestTemplate( BYTE Reader )
{
  ...............................
}

BOOL APIENTRY HandKey_RequestDatalog( BYTE Reader )
{
  ................................
}


The exported functions are Setup, HandKey_RequestTemplate and HandKey_RequestDatalog, so the .DEF file is:

LIBRARY        HANDKEY
DESCRIPTION    'Rutinas que manejan el HandKey Reader'
CODE           PRELOAD MOVEABLE DISCARDABLE
DATA           PRELOAD MOVEABLE SINGLE
EXPORTS        Setup
               HandKey_RequestTemplate
             HandKey_RequestDatalog

When I compile the program, and then link it, I got the following linking error;

Info :Linking E:\Trabajos\HandKey\DLL\handkey.dll
Warn :Warning: Attempt to export non-public symbol 'Setup'
Warn :Warning: Attempt to export non-public symbol 'HandKey_RequestTemplate'
Warn :Warning: Attempt to export non-public symbol 'HandKey_RequestDatalog'

The million question, WHY??????? Why cannot I export those functions????? How can I do it????? I think this problem is related to the use of a class because I have a similar DLL but made in C, not in C++ and it compiles and links well.

Thanks a lot in advance :)
Jaime
0
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Question by:demarcy
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6 Comments
 
LVL 12

Accepted Solution

by:
rwilson032697 earned 180 total points
ID: 1176543
I think you need to add 'export'  to the function declarations.
0
 

Author Comment

by:demarcy
ID: 1176544
rwilson... I have done so and it compiles well.... but in that case, I cannot use the functions in the DLL from an EXE program.

I have in the EXE program the following declarations:

#define DLLIMPORT __declspec(dllimport)

DLLIMPORT BOOL APIENTRY HandKey_RequestTemplate( BYTE );
DLLIMPORT BOOL APIENTRY HandKey_RequestDatalog( BYTE );

When I compile the program, linker gives the errors:
Info :Linking E:\Trabajos\HandKey\DLL\prueba.exe
Error:Error: Unresolved external 'HandKey_RequestTemplate' referenced from module prueba.c
Error:Error: Unresolved external 'HandKey_RequestDatalog' referenced from module prueba.c

How can I import it properly?  The PRUEBA program is in C.

Thanks
Jaime
0
 

Author Comment

by:demarcy
ID: 1176545
One strange thing is that if I use IMPDEF to generate a DEF file of an example program I got:

LIBRARY     DLLSKEL.DLL

EXPORTS
    DLLFunction1                   @1
    DLLFunction2                   @2
    __DebuggerHookData             @3

While if I do it with my program, I get:

LIBRARY     HANDKEY.DLL

EXPORTS
    @HandKey_RequestDatalog$qqsuc  @3   ; HandKey_RequestDatalog(unsigned char)
__stdcall
    @HandKey_RequestTemplate$qqsuc @2   ; HandKey_RequestTemplate(unsigned
char) __stdcall
    @Setup$qqsv                    @1   ; Setup() __stdcall
    __DebuggerHookData             @4

Why is this?
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Author Comment

by:demarcy
ID: 1176546
I've proved that those letters, for example, $qqsv after Setup is placed only by the CPP compiler, how can I do it so that in the LIB file only appear Setup, instead of Setup$qqsv?

Thanks
Jaime
0
 
LVL 12

Expert Comment

by:rwilson032697
ID: 1176547
I think what you are seeing is the name mangling that the compiler does. You need to specify the pascal calling convention (either pascal (or _pascal) or stdcall (or _stdcall)) in the function declarations.

Cheers,

Raymond.
0
 

Author Comment

by:demarcy
ID: 1176548
Thanks.. I have solved the problem.. it was obvious  :)

Bye

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