[Python-checkins] bpo-27987: pymalloc: align by 16bytes on 64bit platform (GH-12850)

[Inada Naoki]

https://github.com/python/cpython/commit/f0be4bbb9b3cee876249c23f2ae6f38f43fa7495
commit: f0be4bbb9b3cee876249c23f2ae6f38f43fa7495
branch: master
author: Inada Naoki <songofacandy at gmail.com>
committer: GitHub <noreply at github.com>
date: 2019-05-14T18:51:15+09:00
summary:

bpo-27987: pymalloc: align by 16bytes on 64bit platform (GH-12850)

files:
A Misc/NEWS.d/next/Core and Builtins/2019-04-16-11-52-21.bpo-27987.n2_DcQ.rst
M Objects/obmalloc.c

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 000000000000..b0f32a5c6c3f
--- /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 7cfd28965967..bd15bcf1363b 100644
--- a/Objects/obmalloc.c
+++ b/Objects/obmalloc.c
@@ -795,8 +795,14 @@ static int running_on_valgrind = -1;
  *
  * 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)