* [Buildroot] [PATCH] package/python: add upstream GCC8 build fix
@ 2018-05-02 11:14 Stefan Becker
2018-05-02 12:52 ` Thomas Petazzoni
2018-05-02 19:30 ` Peter Korsgaard
0 siblings, 2 replies; 3+ messages in thread
From: Stefan Becker @ 2018-05-02 11:14 UTC (permalink / raw)
To: buildroot
Fedora 28 switched to GCC8.
Signed-off-by: Stefan Becker <chemobejk@gmail.com>
---
package/python/0035-GCC8-alignment-fix.patch | 66 ++++++++++++++++++++
1 file changed, 66 insertions(+)
create mode 100644 package/python/0035-GCC8-alignment-fix.patch
diff --git a/package/python/0035-GCC8-alignment-fix.patch b/package/python/0035-GCC8-alignment-fix.patch
new file mode 100644
index 0000000000..34618d9b18
--- /dev/null
+++ b/package/python/0035-GCC8-alignment-fix.patch
@@ -0,0 +1,66 @@
+From 0b91f8a668201fc58fa732b8acc496caedfdbae0 Mon Sep 17 00:00:00 2001
+From: Florian Weimer <fw@deneb.enyo.de>
+Date: Sun, 29 Apr 2018 12:18:33 -0700
+Subject: [PATCH] Indicate that _PyGC_Head is only 8-byte aligned. (closes
+ bpo-33374)
+
+By spec, the "long double" in _PyGC_Head requires the union to always be 16-byte
+aligned. However, obmalloc only yields 8-byte alignment. Compilers including GCC
+8 are starting to use alignment information to do store-merging. So, the "long
+double" needs to be changed to a simple "double" as was long ago done in Python
+3 by e348c8d154cf6342c79d627ebfe89dfe9de23817. For 2.7, we need to add some
+dummy padding to make sure _PyGC_Head stays the same size.
+---
+ Include/objimpl.h | 17 ++++++++++++++++-
+ .../2018-04-29-12-07-00.bpo-33374.-xegL6.rst | 3 +++
+ 2 files changed, 19 insertions(+), 1 deletion(-)
+ create mode 100644 Misc/NEWS.d/next/Core and Builtins/2018-04-29-12-07-00.bpo-33374.-xegL6.rst
+
+Upstream: https://bugs.python.org/issue33374
+Signed-off-by: Stefan Becker <chemobejk@gmail.com>
+---
+
+diff --git a/Include/objimpl.h b/Include/objimpl.h
+index 5f2868332955..cbf6bc3f8763 100644
+--- a/Include/objimpl.h
++++ b/Include/objimpl.h
+@@ -248,6 +248,20 @@ PyAPI_FUNC(PyVarObject *) _PyObject_GC_Resize(PyVarObject *, Py_ssize_t);
+ /* for source compatibility with 2.2 */
+ #define _PyObject_GC_Del PyObject_GC_Del
+
++/*
++ * Former over-aligned definition of PyGC_Head, used to compute the size of the
++ * padding for the new version below.
++ */
++union _gc_head;
++union _gc_head_old {
++ struct {
++ union _gc_head_old *gc_next;
++ union _gc_head_old *gc_prev;
++ Py_ssize_t gc_refs;
++ } gc;
++ long double dummy;
++};
++
+ /* GC information is stored BEFORE the object structure. */
+ typedef union _gc_head {
+ struct {
+@@ -255,7 +269,8 @@ typedef union _gc_head {
+ union _gc_head *gc_prev;
+ Py_ssize_t gc_refs;
+ } gc;
+- long double dummy; /* force worst-case alignment */
++ double dummy; /* Force at least 8-byte alignment. */
++ char dummy_padding[sizeof(union _gc_head_old)];
+ } PyGC_Head;
+
+ extern PyGC_Head *_PyGC_generation0;
+diff --git a/Misc/NEWS.d/next/Core and Builtins/2018-04-29-12-07-00.bpo-33374.-xegL6.rst b/Misc/NEWS.d/next/Core and Builtins/2018-04-29-12-07-00.bpo-33374.-xegL6.rst
+new file mode 100644
+index 000000000000..9ec1a605c8f2
+--- /dev/null
++++ b/Misc/NEWS.d/next/Core and Builtins/2018-04-29-12-07-00.bpo-33374.-xegL6.rst
+@@ -0,0 +1,3 @@
++Tweak the definition of PyGC_Head, so compilers do not believe it is always
++16-byte aligned on x86. This prevents crashes with more aggressive
++optimizations present in GCC 8.
--
2.17.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* [Buildroot] [PATCH] package/python: add upstream GCC8 build fix
2018-05-02 11:14 [Buildroot] [PATCH] package/python: add upstream GCC8 build fix Stefan Becker
@ 2018-05-02 12:52 ` Thomas Petazzoni
2018-05-02 19:30 ` Peter Korsgaard
1 sibling, 0 replies; 3+ messages in thread
From: Thomas Petazzoni @ 2018-05-02 12:52 UTC (permalink / raw)
To: buildroot
Hello Stefan,
On Wed, 2 May 2018 14:14:48 +0300, Stefan Becker wrote:
> Fedora 28 switched to GCC8.
>
> Signed-off-by: Stefan Becker <chemobejk@gmail.com>
I've applied, after fixing one small formatting issue, see below.
> ---
> package/python/0035-GCC8-alignment-fix.patch | 66 ++++++++++++++++++++
> 1 file changed, 66 insertions(+)
> create mode 100644 package/python/0035-GCC8-alignment-fix.patch
>
> diff --git a/package/python/0035-GCC8-alignment-fix.patch b/package/python/0035-GCC8-alignment-fix.patch
> new file mode 100644
> index 0000000000..34618d9b18
> --- /dev/null
> +++ b/package/python/0035-GCC8-alignment-fix.patch
> @@ -0,0 +1,66 @@
> +From 0b91f8a668201fc58fa732b8acc496caedfdbae0 Mon Sep 17 00:00:00 2001
> +From: Florian Weimer <fw@deneb.enyo.de>
> +Date: Sun, 29 Apr 2018 12:18:33 -0700
> +Subject: [PATCH] Indicate that _PyGC_Head is only 8-byte aligned. (closes
> + bpo-33374)
> +
> +By spec, the "long double" in _PyGC_Head requires the union to always be 16-byte
> +aligned. However, obmalloc only yields 8-byte alignment. Compilers including GCC
> +8 are starting to use alignment information to do store-merging. So, the "long
> +double" needs to be changed to a simple "double" as was long ago done in Python
> +3 by e348c8d154cf6342c79d627ebfe89dfe9de23817. For 2.7, we need to add some
> +dummy padding to make sure _PyGC_Head stays the same size.
The Upstream status and SoB should have been here.
> +---
> + Include/objimpl.h | 17 ++++++++++++++++-
> + .../2018-04-29-12-07-00.bpo-33374.-xegL6.rst | 3 +++
> + 2 files changed, 19 insertions(+), 1 deletion(-)
> + create mode 100644 Misc/NEWS.d/next/Core and Builtins/2018-04-29-12-07-00.bpo-33374.-xegL6.rst
> +
> +Upstream: https://bugs.python.org/issue33374
> +Signed-off-by: Stefan Becker <chemobejk@gmail.com>
Not here.
Once again: applied with this issue fixed. Thanks a lot!
Peter: I guess we want this as well for 2018.02.x.
Best regards,
Thomas
--
Thomas Petazzoni, CTO, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Buildroot] [PATCH] package/python: add upstream GCC8 build fix
2018-05-02 11:14 [Buildroot] [PATCH] package/python: add upstream GCC8 build fix Stefan Becker
2018-05-02 12:52 ` Thomas Petazzoni
@ 2018-05-02 19:30 ` Peter Korsgaard
1 sibling, 0 replies; 3+ messages in thread
From: Peter Korsgaard @ 2018-05-02 19:30 UTC (permalink / raw)
To: buildroot
>>>>> "Stefan" == Stefan Becker <chemobejk@gmail.com> writes:
> Fedora 28 switched to GCC8.
> Signed-off-by: Stefan Becker <chemobejk@gmail.com>
Committed to 2018.02.x, thanks.
--
Bye, Peter Korsgaard
^ permalink raw reply [flat|nested] 3+ messages in thread
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2018-05-02 11:14 [Buildroot] [PATCH] package/python: add upstream GCC8 build fix Stefan Becker
2018-05-02 12:52 ` Thomas Petazzoni
2018-05-02 19:30 ` Peter Korsgaard
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