I'm using DMC 8.40 on Win98 SE.
Windows handles (HWND, HINSTANCE, ...) not exported from DLL.
Sample code is:

// ------------------------------------------------
//                 Nothing.h
// ------------------------------------------------
#include <windows.h>
#ifdef CMPDLL
#define EXPALL __declspec(dllexport)
#define EXPVAR __declspec(dllexport) extern
#else
#define EXPALL __declspec(dllimport)
#define EXPVAR __declspec(dllimport) extern
#endif
EXPVAR HWND NoExp;          // Not exported with DMC
EXPVAR int  ExpOk;          // Exported OK
EXPALL int  FunOk(long x);  // Exported OK
// ------------------------------------------------
//                 Nothing.cpp
// ------------------------------------------------
#include "Nothing.h"
BOOL WINAPI DllMain(HINSTANCE h,DWORD d, LPVOID p) {return TRUE;}
EXPALL HWND NoExp = 0;
EXPALL int  ExpOk = 0;
EXPALL int  FunOk(long x) {NoExp=(HWND)x; return ++ExpOk;}
// ------------------------------------------------
//                 Client.cpp
// ------------------------------------------------
#include <stdio.h>
#include "Nothing.h"
int main()
{
printf("DMC DLL Test\n\n");
printf("FunOk(10) returns: %d\n", FunOk(10));
printf("NoExp = %ld    ExpOk = %d\n", NoExp, ExpOk);
printf("Altering NoExp to 20 and ExpOk to 2\n");
NoExp = (HWND)20;
ExpOk = 2;
printf("NoExp = %ld    ExpOk = %d\n", NoExp, ExpOk);
printf("FunOk(30) returns: %d\n", FunOk(30));
printf("NoExp = %ld    ExpOk = %d\n", NoExp, ExpOk);
printf("\n\nPress Enter to quit:");
getchar();
return (0);
}
// ------------------------------------------------
//                DMC Command Line
// ------------------------------------------------
Building DLL / Compiler output:
>dmc -oNothing.dll -L/implib -WD -mn -DCMPDLL Nothing.cpp kernel32.lib user32.lib gdi32.lib
link Nothing,Nothing.dll,,kernel32+user32+gdi32,Nothing/noi/implib;

Building Client / Compiler output:
>dmc Client.cpp Nothing.lib
link Client,,,Nothing+user32+kernel32/noi;
OPTLINK (R) for Win32  Release 7.50B1
Copyright (C) Digital Mars 1989 - 2001  All Rights Reserved

Client.obj(Client)
Error 42: Symbol Undefined ?NoExp@@3PAXA (void *NoExp)

--- errorlevel 1

----------------------------------------------------------------------------
Final comments:
 Compilation on bcc5.5 and mingw works fine.
 On DMC, "ExpOk" and "FunOk" exporteds ok, but "NoExp" handle is not exported.
 "NoExp" symbol not present in "Nothing.lib" import library.
 DLL Compilation gives no errors or warnings.
 Use of stlport or change .cpp extensions to .c do not solve the problem.
 Any sugestion, please?

The fix for this will go out in the next update. Thanks, -Walter