From 8766cb74e186d3820db0a855ccd780d6d84461f7 Mon Sep 17 00:00:00 2001 From: Inada Naoki Date: Mon, 3 Jun 2019 10:51:32 +0900 Subject: [PATCH] [3.7] bpo-27987: align PyGC_Head to alignof(long double) (GH-13335) (GH-13581) This reverts commit 2156fec1f7a8f9972e90cdbaf404e3fd9eaccb35. Now that https://github.com/python/cpython/commit/1b85f4ec45a5d63188ee3866bd55eb29fdec7fbf is in, this change makes sense. --- Include/objimpl.h | 6 +++++- .../2019-05-15-18-28-43.bpo-27987.FaxuLy.rst | 2 ++ 2 files changed, 7 insertions(+), 1 deletion(-) create mode 100644 Misc/NEWS.d/next/Core and Builtins/2019-05-15-18-28-43.bpo-27987.FaxuLy.rst diff --git a/Include/objimpl.h b/Include/objimpl.h index 057bb50cbda9..0436ba7899d9 100644 --- a/Include/objimpl.h +++ b/Include/objimpl.h @@ -255,7 +255,11 @@ typedef union _gc_head { 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; diff --git a/Misc/NEWS.d/next/Core and Builtins/2019-05-15-18-28-43.bpo-27987.FaxuLy.rst b/Misc/NEWS.d/next/Core and Builtins/2019-05-15-18-28-43.bpo-27987.FaxuLy.rst new file mode 100644 index 000000000000..98073471ca7e --- /dev/null +++ b/Misc/NEWS.d/next/Core and Builtins/2019-05-15-18-28-43.bpo-27987.FaxuLy.rst @@ -0,0 +1,2 @@ +``PyGC_Head`` structure is aligned to ``long double``. This is needed to +ensure GC-ed objects are aligned properly. Patch by Inada Naoki. -- 2.47.3