set-register-server-error-reporter sets up a function func that is called to report when calls and automatic calls to register-server or unregister-server via the system-defined entry points of a DLL fail.
The automatic calls happen when registering/unregistering a LispWorks DLL that was saved or delivered with the keyword
:com in its
:dll-exports (see Making a COM DLL with LispWorks). If such a call fails, func is invoked with the name of the function that failed (currently either register-server or unregister-server) and the condition. func should report the failure in a useful way, which would normally mean logging it in a place where you can inspect it later.
DllUnregisterServer) should normally print an error too. For example,
regsvr32would raise a dialog by default. However, this dialog will not contain any information about what failed inside Lisp.
set-register-server-error-reporter) any such error is simply printed to standard output.
cl:invoke-debugger, which may sometimes be useful during development.
LispWorks COM/Automation User Guide and Reference Manual - 23 Mar 2017