How To Call C Functions That Use the _cdecl Calling Convention

MORE INFORMATION

Step-by-Step Example

1. Create a 32-bit Windows C DLL with the following functions:

         long _cdecl PassStr(LPSTR pStr)
         {
          MessageBox (NULL, pStr, "Test DLL", MB_OK);
          return 1;
         }
   
         long _stdcall PassStrStdCall(LPSTR pStr)
         {
          return PassStr(pStr);
         }
   
   						

   Export the functions in a .DEF file as follows:

         LIBRARY   TESTDLL
   
         CODE      PRELOAD MOVEABLE DISCARDABLE
         DATA      PRELOAD SINGLE
   
         EXPORTS
         PassStr            @1
         PassStrStdCall     @2
   
   						

   Name this DLL Testdll.dll, and save the file to the Windows\System directory in Windows 95 or Windows 98, or the Windows\System32 directory in Windows NT or Windows 2000.
2. Create a new project in Visual Basic. Form1 is created by default. Add the following code to the general declarations portion of Form1:

         Private Declare Function PassStrStdCall Lib "testdll.dll" _
                                      (ByVal s As String) As Long
   
         Private Sub Form_Click()
            ret& = PassStrStdCall("hello")
            Print ret&
         End Sub
   
   					

3. Run the Visual Basic program, and click the form. A Msgbox will show the value of the passed string.