@@ -175,9 +175,9 @@ mi_heap_t* _mi_heap_main_get(void) {
 
 // note: in x64 in release build `sizeof(mi_thread_data_t)` is under 4KiB (= OS page size).
 typedef struct mi_thread_data_s {
-  mi_heap_t  heap;  // must come first due to cast in `_mi_heap_done`
+  mi_heap_t  heap;   // must come first due to cast in `_mi_heap_done`
   mi_tld_t   tld;
-  mi_memid_t memid;
+  mi_memid_t memid;  // must come last due to zero'ing
 } mi_thread_data_t;
 
 
@@ -223,7 +223,7 @@ static mi_thread_data_t* mi_thread_data_zalloc(void) {
   }
 
   if (td != NULL && !is_zero) {
-    _mi_memzero_aligned(td, sizeof(*td));
+    _mi_memzero_aligned(td, offsetof(mi_thread_data_t,memid));
   }
   return td;
 }
Original file line number	Diff line number	Diff line change
@@ -175,9 +175,9 @@ mi_heap_t* _mi_heap_main_get(void) {
175	175
176	176	// note: in x64 in release build `sizeof(mi_thread_data_t)` is under 4KiB (= OS page size).
177	177	typedef struct mi_thread_data_s {
178		- mi_heap_t heap; // must come first due to cast in `_mi_heap_done`
	178	+ mi_heap_t heap; // must come first due to cast in `_mi_heap_done`
179	179	mi_tld_t tld;
180		- mi_memid_t memid;
	180	+ mi_memid_t memid; // must come last due to zero'ing
181	181	} mi_thread_data_t;
182	182
183	183
@@ -223,7 +223,7 @@ static mi_thread_data_t* mi_thread_data_zalloc(void) {
223	223	}
224	224
225	225	if (td != NULL && !is_zero) {
226		- _mi_memzero_aligned(td, sizeof(*td));
	226	+ _mi_memzero_aligned(td, offsetof(mi_thread_data_t,memid));
227	227	}
228	228	return td;
229	229	}