+
+ This version is intended to be only used for variables of static
+ lifetime (which are not feasible to protect using the per-instance
+ mechanism of the smob classes) but possibly varying content. As a
+ result, the protection mechanism being used is the irreversible
+ scm_permanent_object. The destructor (typically called after the
+ end of program execution) does not free resources and consequently
+ does not require the memory subsystem to be still workable. A
+ working memory subsystem is only required once a non-immediate
+ Scheme value is assigned to the variable. Since creation of a
+ non-immediate Scheme value requires a working memory subsystem in
+ the first place, this is not really a restriction.
+
+ To avoid accidental creation of temporaries, the copy constructor is
+ made unavailable.