PRB: CPropertySheet::DoModal() or Create() Causes an Exception

• The Microsoft Foundation Classes (MFC) included with: - Microsoft Visual C++, 32-bit Edition, versions 4.0, 4.1, 4.2, 5.0

SYMPTOMS

Calling CPropertySheet::DoModal() or CPropertySheet::Create() in Windows 95 may cause an exception. The Output window displays a message that says the following:

   First-chance exception in <program.exe> (Comctl32.dll): 0xC0000005:
   Access Violation.

CAUSE

The CommCtl32.dll tries to modify the resources for the pages. Since the resources are normally in read-only sections this throws an Exception that can be caught in the application. However, if the application does not catch this exception then the OS will handle this exception correctly.

RESOLUTION

The first-chance exception can be ignored because it is safely handled by the operating system.

One way to prevent the exception from being thrown is to make the resources read/write. You can do this by adding a linker setting of "/SECTION:.rsrc,rw."

A second way to prevent the exception being thrown is to change the font of the pages so they are not "MS Sans Serif". MFC checks the dialog template font for the page. If it is not "MS Sans Serif" then it makes a copy of the resource in read/write memory, modifies the font and passes this to the C mCtl32.dll. So when the dll writes to the template for the page it is writing to read/write memory and hence exception is not thrown.

Another way to prevent the exception from affecting your application is not to have the call for creating the property sheet in a try/catch(...) block. Instead catch particular exceptions in the catch block.

If the property sheet is part of an OLE Automation Server that can be invoked through a method of the server then you have to make the resources read/write, using either of the first two methods described above, since OLE catches the exception.

NOTE: Making the resources Read/Write can cause the resources to be written to a page file.

STATUS

This behavior is by design.

MORE INFORMATION

Sample Code

   /* Compile options needed: default
   */

   /***** this code will cause unpredictable results *****/
   try
   {
       sheet.DoModal();
   }
   catch(...)
   {
   }

   /***** this code is OK *****/
   try
   {
       if (0 == sheet.DoModal())
           throw "DoModal() failed!";
   }
   catch(char * str)
   {
       TRACE ("Exception thrown: %s\n", str);
   }

REFERENCES

For more information, please see the following article in the Microsoft Knowledge Base:

   ARTICLE ID: Q126630
   TITLE     : Resource Sections are Read-only

Keywords          : MfcUI kbprg
Technology        : kbMfc
Version           : WINDOWS NT:4.0 4.1 4.2 5.0;
Platform          : NT WINDOWS
Issue type        : kbprb