bpo-27987: pymalloc: align by 16bytes on 64bit platform (GH-12850)
diff --git a/Misc/NEWS.d/next/Core and Builtins/2019-04-16-11-52-21.bpo-27987.n2_DcQ.rst b/Misc/NEWS.d/next/Core and Builtins/2019-04-16-11-52-21.bpo-27987.n2_DcQ.rst
new file mode 100644
index 0000000..b0f32a5
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2019-04-16-11-52-21.bpo-27987.n2_DcQ.rst
@@ -0,0 +1,3 @@
+pymalloc returns memory blocks aligned by 16 bytes, instead of 8 bytes, on
+64-bit platforms to conform x86-64 ABI. Recent compilers assume this alignment
+more often. Patch by Inada Naoki.
diff --git a/Objects/obmalloc.c b/Objects/obmalloc.c
index 7cfd289..bd15bcf 100644
--- a/Objects/obmalloc.c
+++ b/Objects/obmalloc.c
@@ -795,8 +795,14 @@
*
* You shouldn't change this unless you know what you are doing.
*/
+
+#if SIZEOF_VOID_P > 4
+#define ALIGNMENT 16 /* must be 2^N */
+#define ALIGNMENT_SHIFT 4
+#else
#define ALIGNMENT 8 /* must be 2^N */
#define ALIGNMENT_SHIFT 3
+#endif
/* Return the number of bytes in size class I, as a uint. */
#define INDEX2SIZE(I) (((uint)(I) + 1) << ALIGNMENT_SHIFT)