In pre-2.x Guile, ‘gc-stats’ returns an alist w/ keys:

 gc-time-taken
 cells-allocated
 total-cells-allocated
 cell-heap-size
 bytes-malloced
 gc-malloc-threshold
 gc-times
 gc-mark-time-taken
 cells-marked
 cells-swept
 malloc-yield
 cell-yield
 protected-objects
 cell-heap-segments

In Guile 2.0.6, the keys are now:

 gc-time-taken
 heap-size
 heap-free-size
 heap-total-allocated
 heap-allocated-since-gc
 protected-objects gc-times

I think the NEWS should mention this change and the documentation should
summarize what the fields mean.  Practically speaking, i am interested
mostly in the 2.x equivalent for pre-2.x ‘bytes-malloced’, as its lack
causes Guile-SDL to fail "make check DEBUG=1":