How to Obtain the Version of VBRUN300.DLL

• Standard, Professional, and Enterprise Editions of Microsoft Visual Basic, 16-bit and 32-bit, for Windows, version 4.0
• Standard and Professional Editions of Microsoft Visual Basic for Windows, version 3.0

SUMMARY

The function VBGetVersion(), documented in the Visual Basic API Reference file, returns the constant for version 3.0 in both Versions 3.0 and 4.0 of Visual Basic. This return value was preserved in order to maintain compatibility with many existing .VBX files that check for a version constant. This article describes a technique you can use to obtain the true version of Visual Basic.

MORE INFORMATION

At address SS:0020 (Hex), Visual Basic will load the address of a function table when a Visual Basic program is running. This address is always fixed, although the address will depend on whether the program is run from the design environment or being run as an executable. VBRUN300.DLL contained in Version 3.0 always loads an address different from the version 4.0 equivalent. The following table details these addresses. The 16-Bit Hexadecimal address found at SS:0020 for a Visual Basic program:

   Mode                    Version 3.0    Version 4.0
   --------------------------------------------------
   Design/Run Mode         142E           39D2
   Run as Executable       01ED           1A90

It is important to note that the addresses listed in this article will probably change in any future releases of Visual Basic. Therefore a control developer should account for the fact that the technique described below may provide incorrect results with any future releases.

Step-by-Step Example

1. Start a new project to make a DLL. In this example, Visual C++ version 1.52 was used as the compiler. First create a DEF file as below:

      LIBRARY              GetVersionVB
      DESCRIPTION          'GetVersion Can be called from Visual Basic'
      EXETYPE              WINDOWS 3.1
      CODE                 PRELOAD MOVEABLE DISCARDABLE
      DATA                 PRELOAD MOVEABLE SINGLE
      HEAPSIZE             4096
      EXPORTS
                           GetVersionVB @1
   
   

2. Create a new source code file containing the following code. This code retrieves the address at SS:0020 (Hex) and compares it with the predefined values:

      #include <windows.h>
      #include <vbapi.h>
   
      int FAR PASCAL LibMain (HANDLE hInstance, WORD wDataSeg, WORD wHeapSize,
         LPSTR lpszCmdLine)
      {
         if (wHeapSize > 0)
            UnlockData (0);  //Unlocks the data segment of the library.
         return 1;
      }
   
      WORD FAR PASCAL _export GetVersionVB( void )
      {
         unsigned short nVerConst;
         nVerConst=VBGetVersion(); //Call VB API
   
         if (nVerConst==VB100_VERSION)  //Constant VB100_VERSION in vbapi.h
            return 1;
   
         if (nVerConst==VB200_VERSION)
            return 2;
   
         if (nVerConst==VB300_VERSION)
         {
   
            WORD SS20;
   
            _asm  {                 //Retrieve function table address at SS20
                  mov ax, SS:[0x0020];
                  mov SS20, ax;
                  }
   
            if ( (SS20==0x01ED) || (SS20==0x142E) )
            {
               return 3;
            }
   
            if ( (SS20==0x39D2) || (SS20==0x1A90) )
            {
               return 4;
            }
         }
   
   // If we reach this point, none of the addresses were correct
   // possibly indicating a new release of VB - so the code returns 0
   
   

   int FAR PASCAL _export WEP(int nParam)
   {
      return 1;
   }