DOCUMENT:Q168111 04-MAY-2001 [visualc] TITLE :FIX: #import Does Not Compensate for Gaps in vtable PRODUCT :Microsoft C Compiler PROD/VER:winnt:5.0 OPER/SYS: KEYWORDS:kbtool kbCompiler kbVC500bug kbVS97sp1fix ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - The C/C++ Compiler (CL.EXE), used with: - Microsoft Visual C++, 32-bit Enterprise Edition, version 5.0 - Microsoft Visual C++, 32-bit Professional Edition, version 5.0 ------------------------------------------------------------------------------- SYMPTOMS ======== An access violation may occur when you #import a type library of a COM object that was produced by Visual Basic 5.0. CAUSE ===== The compiler does not compensate for gaps in the vtable left by Visual Basic for properties that are Objects. The sample code below demonstrates this problem. STATUS ====== Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This bug has been corrected in Visual Studio 97 Service Pack 1. For additional information about the Visual Studio 97 Service Pack 1, please see the following article in the Microsoft Knowledge Base: Q170365 INFO: Visual Studio 97 Service Packs - What, Where, and Why MORE INFORMATION ================ Steps to Reproduce Behavior --------------------------- 1. Place the following Visual Basic code in a Class Module of an ActiveX DLL project: Option Explicit Public Obj As Object Public Val As Long Private Sub Class_Initialize() Val = 2 End Sub 2. Make a native dll from the above code. In this example, it is named Test.dll and the Class Module is named TestClass. 3. Place the following code in a .cpp file: #import "test.dll" no_namespace void func() { _TestClassPtr p( __uuidof(TestClass) ); int i = p->Val; // 0xc0000005 here } When the C++ code is executed, an access violation occurs on the commented line of code. Additional query words: ====================================================================== Keywords : kbtool kbCompiler kbVC500bug kbVS97sp1fix Technology : kbVCsearch kbAudDeveloper kbCVCComp Version : winnt:5.0 Issue type : kbbug Solution Type : kbfix ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. Copyright Microsoft Corporation 2001.