create two idl files: foo.idl and foo2.idl contents of foo.idl: [uuid(1a6e4140-0efb-11d3-babb-00805f8a5dd7)] interface foo{}; contents of foo2.idl interface foo{}; run: xpidl -m typelib foo.idl xpidl -m typelib foo2.idl xpt_link.exe out.xpt foo.xpt foo2.xpt The linker should detect a problem. Instead it goes into an infinite loop in the 'while' loop starting at about line 262

Thanks for catching this. I noticed a similar bug during some earlier forward-decl hacking.

Fixed; the loop to iterate through all the interfaces and remove redundant unresolved interfaces was missing an else clause for the case where the name and namespace matched but the iids differed. It now produces a friendly, informative error message.