From 812479ed6c2c7854f5fafb2366d005845bfff67a Mon Sep 17 00:00:00 2001

From: "Miss Islington (bot)"

 <31488909+miss-islington@users.noreply.github.com>

Date: Sun, 12 Jan 2020 03:41:07 -0800

Subject: [PATCH] 00339: bpo-16575: Disabled checks for union types being

 passed by value

Although the underlying libffi issue remains open, adding these

checks have caused problems in third-party projects which are in

widespread use. See the issue for examples.

The corresponding tests have also been skipped.

(cherry picked from commit c12440c371025bea9c3bfb94945f006c486c2c01)

---

 Lib/ctypes/test/test_structures.py |  3 ++-

 Modules/_ctypes/_ctypes.c          | 18 ++++++++++++++++++

 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/Lib/ctypes/test/test_structures.py b/Lib/ctypes/test/test_structures.py

index 19c4430bea..cdbaa7fbd6 100644

--- a/Lib/ctypes/test/test_structures.py

+++ b/Lib/ctypes/test/test_structures.py

@@ -571,6 +571,7 @@ class StructureTestCase(unittest.TestCase):

             self.assertEqual(f2, [0x4567, 0x0123, 0xcdef, 0x89ab,

                                   0x3210, 0x7654, 0xba98, 0xfedc])

+    @unittest.skipIf(True, 'Test disabled for now - see bpo-16575/bpo-16576')

     def test_union_by_value(self):

         # See bpo-16575

@@ -651,7 +652,7 @@ class StructureTestCase(unittest.TestCase):

         self.assertEqual(test5.nested.an_int, 0)

         self.assertEqual(test5.another_int, 0)

-    #@unittest.skipIf('s390' in MACHINE, 'Test causes segfault on S390')

+    @unittest.skipIf(True, 'Test disabled for now - see bpo-16575/bpo-16576')

     def test_bitfield_by_value(self):

         # See bpo-16576

diff --git a/Modules/_ctypes/_ctypes.c b/Modules/_ctypes/_ctypes.c

index 347a3656b6..b51fcde364 100644

--- a/Modules/_ctypes/_ctypes.c

+++ b/Modules/_ctypes/_ctypes.c

@@ -2401,6 +2401,23 @@ converters_from_argtypes(PyObject *ob)

     for (i = 0; i < nArgs; ++i) {

         PyObject *cnv;

         PyObject *tp = PyTuple_GET_ITEM(ob, i);

+/*

+ *      The following checks, relating to bpo-16575 and bpo-16576, have been

+ *      disabled. The reason is that, although there is a definite problem with

+ *      how libffi handles unions (https://github.com/libffi/libffi/issues/33),

+ *      there are numerous libraries which pass structures containing unions

+ *      by values - especially on Windows but examples also exist on Linux

+ *      (https://bugs.python.org/msg359834).

+ *

+ *      It may not be possible to get proper support for unions and bitfields

+ *      until support is forthcoming in libffi, but for now, adding the checks

+ *      has caused problems in otherwise-working software, which suggests it

+ *      is better to disable the checks.

+ *

+ *      Although specific examples reported relate specifically to unions and

+ *      not bitfields, the bitfields check is also being disabled as a

+ *      precaution.

+

         StgDictObject *stgdict = PyType_stgdict(tp);

         if (stgdict != NULL) {

@@ -2428,6 +2445,7 @@ converters_from_argtypes(PyObject *ob)

                 return NULL;

             }

         }

+ */

         if (_PyObject_LookupAttrId(tp, &PyId_from_param, &cnv) <= 0) {

             Py_DECREF(converters);

-- 

2.24.1