SCM_CARLOC and applications

[Ken Raeburn]

Is it intended that applications should use SCM_CARLOC, or is it
intended for internal use only?

Before realizing it was available, but after discovering that SCM_CAR
was no longer an lvalue, I started making arguments to the Emacs folks
for changing the assumption in Emacs that XCAR(foo) would always be an
addressable lvalue.  (Emacs both assigns to car/cdr slots, and takes
their addresses for simple or complicated data structure
manipulation.)  Async copying GC, anything involving write barriers,
etc... nothing that's being used at the moment, but might not be ruled
out for the future.

If SCM_CARLOC is intended to be part of the interface for applications
to use, it undermines my argument, which I thought was a good one :-),
but makes my current Guile-Emacs changes a lot smaller...