Fix (yet another) odd interaction between selector thunks and compacting GC

This should fix errors of the form

  internal error: scavenge_mark_stack: unimplemented/strange closure
    type 28 @ 0x2b92e5f79960

But since it's quite difficult to reproduce the error, I can't be 100%
certain it's gone.  I certainly can't reproduce it again after the
fix, anyway.

diff --git a/rts/sm/Evac.c b/rts/sm/Evac.c
index bae6ed7..6ca7d85 100644 (file)
--- a/rts/sm/Evac.c
+++ b/rts/sm/Evac.c
@@ -846,6 +846,14 @@ selector_loop:
          if (thunk_selector_depth >= MAX_THUNK_SELECTOR_DEPTH) {
              break;
          }
+
+         // we don't update THUNK_SELECTORS in the compacted
+         // generation, because compaction does not remove the INDs
+         // that result, this causes confusion later.
+         if (Bdescr((P_)selectee)->flags && BF_COMPACTED) {
+             break;
+         }
+
          thunk_selector_depth++;
 
          val = eval_thunk_selector(info->layout.selector_offset,