WLL May Cause a GP Fault While Closing Word

• Microsoft Word for Windows, versions 6.0, 6.0a, 6.0c

SYMPTOMS

A WLL created using the CAPI may cause a general protection (GP) fault while closing Word.

CAUSE

This problem can occur if the WLL tries to subclass Word by unloading the WLL while it's responding to a message.

For example, if you are processing the WM_CLOSE command and call the following CAPI code, a GP fault may occur:

InitWCB( &wcb, 0, NULL, 0 ); AddStringParam( &wcb, "c:\\winword\\subclass.wll" ); wdCommandDispatch( wdDeleteAddIn, 0, wcb.cArgs, wcb.wdoprArgs, lpwdoprNil);

You cannot unload the WLL or un-subclass Word when the WLL contains the code that is responding to the message. More precisely, you cannot terminate the WLL while it is in the middle of responding to the WM_CLOSE message.

STATUS

This is a design feature of Windows.

MORE INFORMATION

Windows sends the WM_CLOSE message to a program when you choose the Close command from the System menu.

REFERENCES

Microsoft Windows SDK "Guide to Programming, Part 2"