From 3f033eadab668fd2d338f44aa95fa77d709170f0 Mon Sep 17 00:00:00 2001
From: Eric Wieser <wieser.eric@gmail.com>
Date: Thu, 6 Jun 2019 23:45:57 -0700
Subject: [PATCH] [2.7] bpo-37188: Fix a divide-by-zero in arrays of size-0
 objects

`itemsize` can be zero when `_type_` is an empty struct or length-0 array.

This line used to be `length * itemsize < 0`, which didn't exhibit this problem.
---
 Lib/ctypes/test/test_arrays.py | 15 +++++++++++++++
 Modules/_ctypes/_ctypes.c      |  2 +-
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/Lib/ctypes/test/test_arrays.py b/Lib/ctypes/test/test_arrays.py
index 29fd422a68cc0d3..ec00d9f9f657ee5 100644
--- a/Lib/ctypes/test/test_arrays.py
+++ b/Lib/ctypes/test/test_arrays.py
@@ -134,6 +134,21 @@ class my_int(c_int):
         t2 = my_int * 1
         self.assertIs(t1, t2)
 
+    def test_empty_element_struct(self):
+        class EmptyStruct(Structure):
+            _fields_ = []
+
+        obj = (EmptyStruct * 2)()  # bpo37188: Floating point exception
+        self.assertEqual(sizeof(obj), 0)
+
+    def test_empty_element_array(self):
+        class EmptyArray(Array):
+            _type_ = c_int
+            _length_ = 0
+
+        obj = (EmptyArray * 2)()  # bpo37188: Floating point exception
+        self.assertEqual(sizeof(obj), 0)
+
     def test_bpo36504_signed_int_overflow(self):
         # The overflow check in PyCArrayType_new() could cause signed integer
         # overflow.
diff --git a/Modules/_ctypes/_ctypes.c b/Modules/_ctypes/_ctypes.c
index d608100243d8b96..bef251ef049d5ef 100644
--- a/Modules/_ctypes/_ctypes.c
+++ b/Modules/_ctypes/_ctypes.c
@@ -1534,7 +1534,7 @@ PyCArrayType_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
     }
 
     itemsize = itemdict->size;
-    if (length > PY_SSIZE_T_MAX / itemsize) {
+    if (itemsize != 0 && length > PY_SSIZE_T_MAX / itemsize) {
         PyErr_SetString(PyExc_OverflowError,
                         "array too large");
         Py_DECREF(stgdict);