bpo-37188: Fix a divide-by-zero in arrays of size-0 objects (#13881)

Lib/ctypes/test/test_arrays.py

@@ -208,6 +208,21 @@ class ArrayTestCase(unittest.TestCase):
             _type_ = c_int
             _length_ = 0
 
+    def test_empty_element_struct(self):
+        class EmptyStruct(Structure):
+            _fields_ = []
+
+        obj = (EmptyStruct * 2)()  # bpo37188: Floating point exception
+        assert sizeof(obj) == 0
+
+    def test_empty_element_array(self):
+        class EmptyArray(Array):
+            _type_ = c_int
+            _length_ = 0
+
+        obj = (EmptyArray * 2)()  # bpo37188: Floating point exception
+        assert sizeof(obj) == 0
+
     def test_bpo36504_signed_int_overflow(self):
         # The overflow check in PyCArrayType_new() could cause signed integer
         # overflow.

Modules/_ctypes/_ctypes.c

@@ -1518,7 +1518,7 @@ 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");
         goto error;