+.PP
+X/Open defines no error conditions.
+.PP
+In this implementation,
+these functions return an error
+if the window pointer is null, or
+if its timeout expires without having any data.
+.PP
+This implementation provides an extension as well.
+If a SIGWINCH interrupts the function, it will return \fBKEY_RESIZE\fP
+rather than \fBOK\fP or \fBERR\fP.