A simple test case seems to indicate that you can longjmp() out of the IOErrorHandler as long as you delete the `Display *' from the XtAppContext (if you don't, select() continuously fails). The bad news is that: a) The XtDeleteFromAppContext function is internal to libXt, and (worse still): b) XtAppContext is an opaque type. It's actually an `_XtAppStruct *', and _XtAppStruct is defined in InitialI.h, which is an internal Xt header. We could just copy the definition, but there's no guarantee that individual vendors haven't made changes to it. IOW: there seems to be a solution, but I don't know whether it can be implemented in a way that doesn't mean that you need the X11 source code to build XEmacs.