From ab35adc682ec51800aa19a77de9947c6aaa50f41 Mon Sep 17 00:00:00 2001

From: Victor Stinner <victor.stinner@gmail.com>

Date: Fri, 6 Oct 2017 22:28:59 +0200

Subject: [PATCH] bpo-31719: Fix test_regrtest.test_crashed() on s390x

Add a new _testcapi._read_null() function to crash Python in a

reliable way on s390x.

On s390x, ctypes.string_at(0) returns an empty string rather than

crashing.

---

 Lib/test/support/__init__.py                            |  4 ++--

 Lib/test/test_regrtest.py                               |  2 ++

 .../next/Tests/2017-10-06-22-37-38.bpo-31719.gHyrV3.rst |  3 +++

 Modules/_testcapimodule.c                               | 17 +++++++++++++++++

 4 files changed, 24 insertions(+), 2 deletions(-)

 create mode 100644 Misc/NEWS.d/next/Tests/2017-10-06-22-37-38.bpo-31719.gHyrV3.rst

diff --git a/Lib/test/support/__init__.py b/Lib/test/support/__init__.py

index ef474e00b68..25df3ed0c41 100644

--- a/Lib/test/support/__init__.py

+++ b/Lib/test/support/__init__.py

@@ -1960,6 +1960,6 @@ def _crash_python():

     Use SuppressCrashReport() to prevent a crash report from popping up.

     """

-    import ctypes

+    import _testcapi

     with SuppressCrashReport():

-        ctypes.string_at(0)

+        _testcapi._read_null()

diff --git a/Lib/test/test_regrtest.py b/Lib/test/test_regrtest.py

index 264c74d22ba..aae274384c7 100644

--- a/Lib/test/test_regrtest.py

+++ b/Lib/test/test_regrtest.py

@@ -543,6 +543,8 @@ def test_method2(self):

                                 testname)

         self.assertEqual(output.splitlines(), all_methods)

+    @unittest.skipIf(sys.platform.startswith('aix'),

+                     "support._crash_python() doesn't work on AIX")

     def test_crashed(self):

         # Any code which causes a crash

         code = 'import test.support; test.support._crash_python()'

diff --git a/Misc/NEWS.d/next/Tests/2017-10-06-22-37-38.bpo-31719.gHyrV3.rst b/Misc/NEWS.d/next/Tests/2017-10-06-22-37-38.bpo-31719.gHyrV3.rst

new file mode 100644

index 00000000000..a06c5267251

--- /dev/null

+++ b/Misc/NEWS.d/next/Tests/2017-10-06-22-37-38.bpo-31719.gHyrV3.rst

@@ -0,0 +1,3 @@

+Fix test_regrtest.test_crashed() on s390x. Add a new _testcapi._read_null()

+function to crash Python in a reliable way on s390x. On s390x,

+ctypes.string_at(0) returns an empty string rather than crashing.

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

index 7691b5188ff..5902de07823 100644

--- a/Modules/_testcapimodule.c

+++ b/Modules/_testcapimodule.c

@@ -2566,6 +2566,22 @@ py_w_stopcode(PyObject *self, PyObject *args)

 #endif

+/* Read memory from NULL (address 0) to raise a SIGSEGV or SIGBUS signal

+   depending on the platform. This function is used by

+   test.support._crash_python() to "crash" Python. */

+static PyObject *

+read_null(PyObject *self, PyObject *args)

+{

+    volatile int *x;

+    volatile int y;

+

+    x = NULL;

+    y = *x;

+    return PyLong_FromLong(y);

+

+}

+

+

 static PyMethodDef TestMethods[] = {

     {"raise_exception",         raise_exception,                 METH_VARARGS},

     {"set_errno",               set_errno,                       METH_VARARGS},

@@ -2685,6 +2701,7 @@ static PyMethodDef TestMethods[] = {

 #ifdef W_STOPCODE

     {"W_STOPCODE", py_w_stopcode, METH_VARARGS},

 #endif

+    {"_read_null", (PyCFunction)read_null, METH_NOARGS},

     {NULL, NULL} /* sentinel */

 };