bpo-27987: align PyGC_Head to alignof(long double) (GH-13335)
diff --git a/Include/objimpl.h b/Include/objimpl.h
index 057bb50..0436ba7 100644
--- a/Include/objimpl.h
+++ b/Include/objimpl.h
@@ -255,7 +255,11 @@
union _gc_head *gc_prev;
Py_ssize_t gc_refs;
} gc;
- double dummy; /* force worst-case alignment */
+ long double dummy; /* force worst-case alignment */
+ // malloc returns memory block aligned for any built-in types and
+ // long double is the largest standard C type.
+ // On amd64 linux, long double requires 16 byte alignment.
+ // See bpo-27987 for more discussion.
} PyGC_Head;
extern PyGC_Head *_PyGC_generation0;