PRB: Script Error Occurs When Referencing Non-variant Array (165967)

MORE INFORMATION

The VBSARRAY is a simple Active Template Library (ATL) version 2.1 component object that demonstrates this behavior. The component implements a dual interface Ivbsa that supports three methods: TestBstrs, TestVariants, and TestPassArray. The first demonstrates the problem by returning a SAFEARRAY of BSTRs. The second demonstrates the solution by packaging each of the BSTRs in a VARIANT. The third demonstrates that an array of non-VARIANT type can be passed from component to VBSCRIPT or JSCRIPT to component. The data remains intact.

Here is the implementation of TestVariants:

      // Return a VARIANT array of VARIANTs which hold BSTRs
      STDMETHODIMP Cvbsa::TestVariants(VARIANT * pvaVariant)
      {
         HRESULT hr = NOERROR;
         LPSAFEARRAY psa;
         SAFEARRAYBOUND rgsabound[]  = { 3, 0 }; // 3 elements, 0-based
         int i;

         if (!pvaVariant)
         {
            return E_INVALIDARG;
         }

         VariantInit(pvaVariant);

         psa = SafeArrayCreate(VT_VARIANT, 1, rgsabound);
         if (!psa)
         {
            return E_OUTOFMEMORY;
         }

         VARIANT vFlavors[3];
         for (i = 0; i < 3; i++)
         {
            VariantInit(&vFlavors[i]);
            V_VT(&vFlavors[i]) = VT_BSTR;
         }

         V_BSTR(&vFlavors[0]) = SysAllocString(OLESTR("Vanilla"));
         V_BSTR(&vFlavors[1]) = SysAllocString(OLESTR("Chocolate"));
         V_BSTR(&vFlavors[2]) = SysAllocString(OLESTR("Espresso Chip"));
         if (!V_BSTR(&vFlavors[0]) || !V_BSTR(&vFlavors[1]) ||
             !V_BSTR(&vFlavors[2]))
         {
            hr = E_OUTOFMEMORY;
            goto Error;
         }

         {
                //Plug references to the data into the SAFEARRAY
               LPVARIANT rgElems;
               if (FAILED(hr = SafeArrayAccessData(psa,(LPVOID*)&rgElems)))

            {
               goto Error;
            }
            for (i = 0; i < 3; i++)
            {
               rgElems[i] = vFlavors[i];
            }
            SafeArrayUnaccessData(psa);
         }

         V_VT(pvaVariant) = VT_ARRAY | VT_VARIANT;
         V_ARRAY(pvaVariant) = psa;

         return NOERROR;

   Error:
         for (i = 0; i < 3; i++)
         {
            if (V_BSTR(&vFlavors[i])
            {
               VariantClear(&vFlavors[i]);
            }
         }
         return hr;
   }
				

Here is the JSCRIPT code from VBSARRAY.HTM, the test page included with the sample, that checks the datatype of a variable:

      <SCRIPT LANGUAGE=JSCRIPT>
      function JScriptSafeArrayTest()
      {
         pvaBstr = SimpleComponent.TestBstrs()
         if (typeof(pvaBstr) == "unknown")
         {
            Alert("JSCRIPT cannot handle the type returned by TestBstrs()")
            SimpleComponent.TestPassedArray(pvaBstr)
         }

         pvaVariant = SimpleComponent.TestVariants()
         if (typeof(pvaVariant) == "unknown")
         {
         Alert("JSCRIPT cannot handle the type returned by TestVariants()")
            SimpleComponent.TestPassedArray(pvaVariant)
         }
      }
      </SCRIPT>
				

To demonstrate the problem and the solution, perform the following steps:

1. Follow the instructions below on obtaining the sample component VBSARRAY.DLL and sample page VBSARRAY.HTM.
2. Register the component VBSARRAY.DLL using a tool such as REGSVR32.EXE.
3. Launch Internet Explorer, and load the test page VBSARRAY.HTM.
4. Follow the instructions on the page, clicking the various buttons and observing the resulting behavior.

The sample component was created using the Active Template Library version 2.1 including with Visual C++ 5.0 in the Visual Studio 97 environment. If you have Visual Studio 97, you can load the VBSARRAY project directly. Otherwise, you can open the relevant source file VBSA.CPP in any editor to see how the SAFEARRAY is constructed in both the VARIANT and the BSTR cases. Search for the implementation of both Cvbsa::TestVariants and Cvbsa::TestBstrs in the source file.

The following files are available for download from the Microsoft Download Center:
For additional information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base: Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help to prevent any unauthorized changes to the file.