[3.12] gh-62260: Fix ctypes.Structure subclassing with multiple layers (GH-13374...

The length field of StgDictObject for Structure class contains now
the total number of items in ffi_type_pointer.elements (excluding
the trailing null).

The old behavior of using the number of elements in the parent class can
cause the array to be truncated when it is copied, especially when there
are multiple layers of subclassing.

(cherry picked from commit 5f3cc90a12d6df404fd6f48a0df1334902e271f2)

Co-authored-by: Jeffrey Kintscher <49998481+websurfer5@users.noreply.github.com>

diff --git a/Lib/test/test_ctypes/test_structures.py b/Lib/test/test_ctypes/test_structures.py
index 466bfcd5a8e2d43fc5ca72382896f2bac93b9183..ce2d1b370c402c5ca2d4048a19414e1395ccd69b 100644 (file)
--- a/Lib/test/test_ctypes/test_structures.py
+++ b/Lib/test/test_ctypes/test_structures.py
@@ -1,4 +1,6 @@
 import platform
+from platform import architecture as _architecture
+import struct
 import sys
 import unittest
 from test.test_ctypes import need_symbol
@@ -7,6 +9,7 @@ from ctypes import (CDLL, Array, Structure, Union, POINTER, sizeof, byref, align
                     c_uint8, c_uint16, c_uint32,
                     c_short, c_ushort, c_int, c_uint,
                     c_long, c_ulong, c_longlong, c_ulonglong, c_float, c_double)
+from ctypes.util import find_library
 from struct import calcsize
 import _ctypes_test
 from collections import namedtuple
@@ -189,7 +192,6 @@ class StructureTestCase(unittest.TestCase):
         self.assertEqual(sizeof(X), 10)
         self.assertEqual(X.b.offset, 2)
 
-        import struct
         longlong_size = struct.calcsize("q")
         longlong_align = struct.calcsize("bq") - longlong_size
 
@@ -480,6 +482,66 @@ class StructureTestCase(unittest.TestCase):
         self.assertEqual(s.first, got.first)
         self.assertEqual(s.second, got.second)
 
+    def _test_issue18060(self, Vector):
+        # The call to atan2() should succeed if the
+        # class fields were correctly cloned in the
+        # subclasses. Otherwise, it will segfault.
+        if sys.platform == 'win32':
+            libm = CDLL(find_library('msvcrt.dll'))
+        else:
+            libm = CDLL(find_library('m'))
+
+        libm.atan2.argtypes = [Vector]
+        libm.atan2.restype = c_double
+
+        arg = Vector(y=0.0, x=-1.0)
+        self.assertAlmostEqual(libm.atan2(arg), 3.141592653589793)
+
+    @unittest.skipIf(_architecture() == ('64bit', 'WindowsPE'), "can't test Windows x64 build")
+    @unittest.skipUnless(sys.byteorder == 'little', "can't test on this platform")
+    def test_issue18060_a(self):
+        # This test case calls
+        # PyCStructUnionType_update_stgdict() for each
+        # _fields_ assignment, and PyCStgDict_clone()
+        # for the Mid and Vector class definitions.
+        class Base(Structure):
+            _fields_ = [('y', c_double),
+                        ('x', c_double)]
+        class Mid(Base):
+            pass
+        Mid._fields_ = []
+        class Vector(Mid): pass
+        self._test_issue18060(Vector)
+
+    @unittest.skipIf(_architecture() == ('64bit', 'WindowsPE'), "can't test Windows x64 build")
+    @unittest.skipUnless(sys.byteorder == 'little', "can't test on this platform")
+    def test_issue18060_b(self):
+        # This test case calls
+        # PyCStructUnionType_update_stgdict() for each
+        # _fields_ assignment.
+        class Base(Structure):
+            _fields_ = [('y', c_double),
+                        ('x', c_double)]
+        class Mid(Base):
+            _fields_ = []
+        class Vector(Mid):
+            _fields_ = []
+        self._test_issue18060(Vector)
+
+    @unittest.skipIf(_architecture() == ('64bit', 'WindowsPE'), "can't test Windows x64 build")
+    @unittest.skipUnless(sys.byteorder == 'little', "can't test on this platform")
+    def test_issue18060_c(self):
+        # This test case calls
+        # PyCStructUnionType_update_stgdict() for each
+        # _fields_ assignment.
+        class Base(Structure):
+            _fields_ = [('y', c_double)]
+        class Mid(Base):
+            _fields_ = []
+        class Vector(Mid):
+            _fields_ = [('x', c_double)]
+        self._test_issue18060(Vector)
+
     def test_array_in_struct(self):
         # See bpo-22273
 

diff --git a/Misc/NEWS.d/next/Library/2019-05-17-07-22-33.bpo-18060.5mqTQM.rst b/Misc/NEWS.d/next/Library/2019-05-17-07-22-33.bpo-18060.5mqTQM.rst
new file mode 100644 (file)
index 0000000..3fefbc3
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2019-05-17-07-22-33.bpo-18060.5mqTQM.rst
@@ -0,0 +1,2 @@
+Fixed a class inheritance issue that can cause segfaults when deriving two or more levels of subclasses from a base class of Structure or Union.
+

diff --git a/Modules/_ctypes/_ctypes.c b/Modules/_ctypes/_ctypes.c
index 534ef8c1d6cf8f4b9e4bc027c09036d266006baf..c5157560f6e0d064e989764a295aeb3a9308926f 100644 (file)
--- a/Modules/_ctypes/_ctypes.c
+++ b/Modules/_ctypes/_ctypes.c
@@ -4352,10 +4352,10 @@ _init_pos_args(PyObject *self, PyTypeObject *type,
         return index;
     }
 
-    for (i = 0;
-         i < dict->length && (i+index) < PyTuple_GET_SIZE(args);
+    for (i = index;
+         i < dict->length && i < PyTuple_GET_SIZE(args);
          ++i) {
-        PyObject *pair = PySequence_GetItem(fields, i);
+        PyObject *pair = PySequence_GetItem(fields, i - index);
         PyObject *name, *val;
         int res;
         if (!pair)
@@ -4365,7 +4365,7 @@ _init_pos_args(PyObject *self, PyTypeObject *type,
             Py_DECREF(pair);
             return -1;
         }
-        val = PyTuple_GET_ITEM(args, i + index);
+        val = PyTuple_GET_ITEM(args, i);
         if (kwds) {
             res = PyDict_Contains(kwds, name);
             if (res != 0) {
@@ -4386,7 +4386,7 @@ _init_pos_args(PyObject *self, PyTypeObject *type,
         if (res == -1)
             return -1;
     }
-    return index + dict->length;
+    return dict->length;
 }
 
 static int

diff --git a/Modules/_ctypes/stgdict.c b/Modules/_ctypes/stgdict.c
index 451dcdc66f5491e17037af44525dbe6f0d2662c4..844c7b1c48de014af1cf278c1ccbb7f57c24b8de 100644 (file)
--- a/Modules/_ctypes/stgdict.c
+++ b/Modules/_ctypes/stgdict.c
@@ -694,7 +694,7 @@ PyCStructUnionType_update_stgdict(PyObject *type, PyObject *fields, int isStruct
 
     stgdict->size = aligned_size;
     stgdict->align = total_align;
-    stgdict->length = len;      /* ADD ffi_ofs? */
+    stgdict->length = ffi_ofs + len;
 
 /*
  * The value of MAX_STRUCT_SIZE depends on the platform Python is running on.