+ // We don't want to end up in to-space, because this causes
+ // problems when the GC later tries to evacuate the result of
+ // eval_thunk_selector(). There are various ways this could
+ // happen:
+ //
+ // 1. following an IND_STATIC
+ //
+ // 2. when the old generation is compacted, the mark phase updates
+ // from-space pointers to be to-space pointers, and we can't
+ // reliably tell which we're following (eg. from an IND_STATIC).
+ //
+ // 3. compacting GC again: if we're looking at a constructor in
+ // the compacted generation, it might point directly to objects
+ // in to-space. We must bale out here, otherwise doing the selection
+ // will result in a to-space pointer being returned.
+ //
+ // (1) is dealt with using a BF_EVACUATED test on the
+ // selectee. (2) and (3): we can tell if we're looking at an
+ // object in the compacted generation that might point to
+ // to-space objects by testing that (a) it is BF_COMPACTED, (b)
+ // the compacted generation is being collected, and (c) the
+ // object is marked. Only a marked object may have pointers that
+ // point to to-space objects, because that happens when
+ // scavenging.
+ //
+ // The to-space test is now embodied in the in_to_space() inline
+ // function, as it is re-used below.
+ //
+ if (is_to_space(selectee)) {
+ goto bale_out;
+ }
+