exit-dialog is the means to successfully return a value from the current dialog. Hence, it might be called from an
button so that pressing the button would cause the dialog to return successfully, while the
button would call the counterpart function abort-dialog.
If there is no current dialog then
exit-dialog does nothing and returns
nil. If there is a current dialog then
exit-dialog either returns non-nil or does a non-local exit. Therefore code that depends on
exit-dialog returning must be written carefully - see the discussion under abort-dialog for details.
CAPI User Guide and Reference Manual (Macintosh version) - 25 Feb 2015