Fix #10701 & 10838

Author: Safety0ff

src/gc/gc.d

@@ -2630,7 +2630,7 @@ struct Gcx
                                 toClear |= GCBits.BITS_1 << clearIndex;
 
                                 List *list = cast(List *)p;
-                                debug(PRINTF) printf("\tcollecting %p\n", list);
+                                debug(COLLECT_PRINTF) printf("\tcollecting %p\n", list);
                                 log_free(sentinel_add(list));
 
                                 debug (MEMSTOMP) memset(p, 0xF3, size);
@@ -2744,11 +2744,15 @@ struct Gcx
             {
                 biti = (offset & notbinsize[bins]) >> pool.shiftBy;
             }
-            else
+            else if(bins == B_PAGEPLUS)
             {
                 pn -= pool.bPageOffsets[pn];
                 biti = pn * (PAGESIZE >> pool.shiftBy);
             }
+            else // bins == B_FREE
+            {
+                return IsMarked.no;
+            }
             return pool.mark.test(biti) ? IsMarked.yes : IsMarked.no;
         }
         return IsMarked.unknown;