FIX: Navigate(2) Causes Access Violation in Shdocvw.dll (182490)

The information in this article applies to:

Microsoft Internet Explorer (Programming) 3.0
Microsoft Internet Explorer (Programming) 3.01
Microsoft Internet Explorer (Programming) 3.02
Microsoft Internet Explorer (Programming) 4.0
Microsoft Internet Explorer (Programming) 4.01

This article was previously published under Q182490

SYMPTOMS

Calling Navigate or Navigate2 causes an access violation in Shdocvw.dll. The error that is reported is "(showdocvw.dll): 0xC0000005: Access Violation".

CAUSE

This is caused by passing NULLs to the Navigate or Navigate2 methods like this:

m_WebBrowser.Navigate2(pUrl, NULL, NULL, NULL, NULL);

Navigate(2) expects a pointers to VARIANTs. The access violation is due to the fact that the WebBrowser control is trying to write to the memory pointed to by one of these parameters. When you pass NULL for one or more of these parameters, the WebBrowser control tries to write to the NULL memory. This causes the access violation.

RESOLUTION

You must pass the address of empty VARIANTs to the Navigate or Navigate2 methods.

Typically, this can be accomplished with the following C++ code:

VARIANT vtEmpty;
vtEmpty.vt = VT_EMPTY;

However, using the compiler's native support for OLE is usually much easier. Use the following code to take advantage of the compiler's native support.

_variant_t vtEmpty;
// nothing further needed

If you are using MFC, the COleVariant class can be used to created an empty VARIANT. The default constructor for COleVariant sets the type of the VARIANT to VT_EMPTY. Here is the MFC code:

COleVariant vtEmpty;

Then, you pass the vtEmpty variable to the Navigate or Navigate2 method like so:

m_WebBrowser.Navigate2(pUrl, &vtEmpty, &vtEmpty, &vtEmpty, &vtEmpty);

STATUS

Microsoft has confirmed that this is a bug in the Microsoft products that are listed at the beginning of this article. This bug was corrected in Microsoft Internet Explorer 5.

REFERENCES

Please see the "Reusing the WebBrowser" and "Reusing MSHTML" subsections of the "Internet Tools and Technologies" section in the Internet Client SDK online help:

http://msdn.microsoft.com/workshop/essentials/inetsdk/inetsdk_map.asp

Modification Type:	Minor	Last Reviewed:	3/16/2005
Keywords:	kbBug kberrmsg kbfix kbie500fix KB182490