ensure thread delayed freeing is correct during heap_absorb; #204

src/heap.c

@@ -338,6 +338,8 @@ static void mi_heap_absorb(mi_heap_t* heap, mi_heap_t* from) {
   
   // transfer all pages by appending the queues; this will set a new heap field 
   // so threads may do delayed frees in either heap for a while.
+  // note: appending waits for each page to not be in the `MI_DELAYED_FREEING` state
+  // so after this only the new heap will get delayed frees
   for (size_t i = 0; i <= MI_BIN_FULL; i++) {
     mi_page_queue_t* pq = &heap->pages[i];
     mi_page_queue_t* append = &from->pages[i];
@@ -351,7 +353,7 @@ static void mi_heap_absorb(mi_heap_t* heap, mi_heap_t* from) {
   // note: be careful here as the `heap` field in all those pages no longer point to `from`,
   // turns out to be ok as `_mi_heap_delayed_free` only visits the list and calls a 
   // the regular `_mi_free_delayed_block` which is safe.
-  _mi_heap_delayed_free(from);
+  _mi_heap_delayed_free(from);  
   mi_assert_internal(from->thread_delayed_free == NULL);
 
   // and reset the `from` heap

src/page-queue.c

@@ -329,6 +329,7 @@ static void mi_page_queue_enqueue_from(mi_page_queue_t* to, mi_page_queue_t* fro
   mi_page_set_in_full(page, mi_page_queue_is_full(to));
 }
 
+// Only called from `mi_heap_absorb`.
 size_t _mi_page_queue_append(mi_heap_t* heap, mi_page_queue_t* pq, mi_page_queue_t* append) {
   mi_assert_internal(mi_heap_contains_queue(heap,pq));
   mi_assert_internal(pq->block_size == append->block_size);
@@ -339,6 +340,10 @@ size_t _mi_page_queue_append(mi_heap_t* heap, mi_page_queue_t* pq, mi_page_queue
   size_t count = 0;
   for (mi_page_t* page = append->first; page != NULL; page = page->next) {
     mi_page_set_heap(page,heap);
+    // set it to delayed free (not overriding NEVER_DELAYED_FREE) which has as a
+    // side effect that it spins until any DELAYED_FREEING is finished. This ensures
+    // that after appending only the new heap will be used for delayed free operations.
+    _mi_page_use_delayed_free(page, MI_USE_DELAYED_FREE, false);
     count++;
   }
 

test/main-override.cpp

@@ -28,7 +28,7 @@ int main() {
   mi_stats_reset();  // ignore earlier allocations
   // heap_no_delete();  // issue #202
   // heap_late_free();  // issue #204
-  // various_tests();
+  various_tests();
   mi_stats_print(NULL);
   return 0;
 }