do not reclaim segments if free-ing from a thread with an already abandoned heap (issue #944)

Author: daanx

src/free.c

@@ -236,11 +236,12 @@ static void mi_decl_noinline mi_free_block_delayed_mt( mi_page_t* page, mi_block
 static void mi_decl_noinline mi_free_block_mt(mi_page_t* page, mi_segment_t* segment, mi_block_t* block)
 {
   // first see if the segment was abandoned and if we can reclaim it into our thread
-  if (mi_option_is_enabled(mi_option_abandoned_reclaim_on_free) &&
+  if (_mi_option_get_fast(mi_option_abandoned_reclaim_on_free) != 0 &&
       #if MI_HUGE_PAGE_ABANDON
       segment->page_kind != MI_PAGE_HUGE &&
       #endif
-      mi_atomic_load_relaxed(&segment->thread_id) == 0)
+      mi_atomic_load_relaxed(&segment->thread_id) == 0 &&  // segment is abandoned?
+      mi_prim_get_default_heap() != (mi_heap_t*)&_mi_heap_empty) // and we did not already exit this thread (without this check, a fresh heap will be initalized (issue #944))
   {
     // the segment is abandoned, try to reclaim it into our heap
     if (_mi_segment_attempt_reclaim(mi_heap_get_default(), segment)) {