fix issue #204 (and #205) by doing thread delayed free after absorbing the pages

src/heap.c

@@ -312,33 +312,29 @@ static void mi_heap_absorb(mi_heap_t* heap, mi_heap_t* from) {
   mi_assert_internal(heap!=NULL);
   if (from==NULL || from->page_count == 0) return;
 
-  // unfull all full pages in the `from` heap
-  mi_page_t* page = from->pages[MI_BIN_FULL].first;
-  while (page != NULL) {
-    mi_page_t* next = page->next;
-    _mi_page_unfull(page);
-    page = next;
-  }
-  mi_assert_internal(from->pages[MI_BIN_FULL].first == NULL);
-
-  // free outstanding thread delayed free blocks
+  // reduce the size of the delayed frees
   _mi_heap_delayed_free(from);
-
-  // transfer all pages by appending the queues; this will set
-  // a new heap field which is ok as all pages are unfull'd and thus
-  // other threads won't access this field anymore (see `mi_free_block_mt`)
-  for (size_t i = 0; i < MI_BIN_FULL; i++) {
+  
+  // 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.
+  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];
     size_t pcount = _mi_page_queue_append(heap, pq, append);
     heap->page_count += pcount;
     from->page_count -= pcount;
   }
-  mi_assert_internal(from->thread_delayed_free == NULL);
   mi_assert_internal(from->page_count == 0);
 
+  // and do outstanding delayed frees in the `from` heap  
+  // 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_assert_internal(from->thread_delayed_free == NULL);
+
   // and reset the `from` heap
-  mi_heap_reset_pages(from);
+  mi_heap_reset_pages(from);  
 }
 
 // Safe delete a heap without freeing any still allocated blocks in that heap.

test/main-override.cpp

@@ -12,21 +12,27 @@
 #include <mimalloc.h>
 #include <assert.h>
 
-// Issue #202
-void thread_main() {
-  mi_heap_t* heap = mi_heap_new();
-  void* q = mi_heap_malloc(heap,1024);
-  // mi_heap_delete(heap); // uncomment to prevent assertion
-}
+#ifdef _WIN32
+#include <windows.h>
+static void msleep(unsigned long msecs) { Sleep(msecs); }
+#else
+#include <unistd.h>
+static void msleep(unsigned long msecs) { usleep(msecs * 1000UL); }
+#endif
+
+void heap_no_delete();
+void heap_late_free();
+void various_tests();
 
 int main() {
-  auto t1 = std::thread(thread_main);
-  t1.join();
+  mi_stats_reset();  // ignore earlier allocations
+  // heap_no_delete();  // issue #202
+  // heap_late_free();  // issue #204
+  various_tests();
+  mi_stats_print(NULL);
   return 0;
 }
 
-/*
-
 static void* p = malloc(8);
 
 void free_p() {
@@ -43,8 +49,7 @@ public:
 };
 
 
-int main() {
-  mi_stats_reset();  // ignore earlier allocations
+void various_tests() {  
   atexit(free_p);
   void* p1 = malloc(78);
   void* p2 = mi_malloc_aligned(16,24);
@@ -68,8 +73,6 @@ int main() {
   delete t;
   t = new (std::nothrow) Test(42);
   delete t;  
-  mi_stats_print(NULL);
-  return 0;
 }
 
 class Static {
@@ -104,4 +107,37 @@ bool test_stl_allocator2() {
   vec.pop_back();
   return vec.size() == 0;
 }
-*/
+
+
+
+// Issue #202
+void heap_no_delete_worker() {
+  mi_heap_t* heap = mi_heap_new();
+  void* q = mi_heap_malloc(heap,1024);
+  // mi_heap_delete(heap); // uncomment to prevent assertion
+}
+
+void heap_no_delete() {
+  auto t1 = std::thread(heap_no_delete_worker);
+  t1.join();  
+}
+
+
+// Issue #204
+volatile void* global_p;
+
+void t1main() {
+  mi_heap_t* heap = mi_heap_new();
+  global_p = mi_heap_malloc(heap, 1024);
+  mi_heap_delete(heap);
+}
+
+void heap_late_free() {
+  auto t1 = std::thread(t1main);
+
+  msleep(2000);
+  assert(global_p);
+  mi_free((void*)global_p);
+
+  t1.join();
+}