Patch #1521817: The index range checking on ctypes arrays containing

exactly one element is enabled again.

Lib/ctypes/test/test_varsize_struct.py

@@ -46,70 +46,5 @@ class VarSizeTest(unittest.TestCase):
         self.failUnlessRaises(IndexError, array.__setitem__, -1, None)
         self.failUnlessRaises(IndexError, array.__getitem__, -1)
 
-    def test_varsized_array(self):
-        array = (c_int * 20)(20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
-
-        # no range checking is done on arrays with size == 1
-        varsize_array = (c_int * 1).from_address(addressof(array))
-
-        # __getitem__
-        self.failUnlessEqual(varsize_array[0], 20)
-        self.failUnlessEqual(varsize_array[1], 21)
-        self.failUnlessEqual(varsize_array[2], 22)
-        self.failUnlessEqual(varsize_array[3], 23)
-        self.failUnlessEqual(varsize_array[4], 24)
-        self.failUnlessEqual(varsize_array[5], 25)
-        self.failUnlessEqual(varsize_array[6], 26)
-        self.failUnlessEqual(varsize_array[7], 27)
-        self.failUnlessEqual(varsize_array[8], 28)
-        self.failUnlessEqual(varsize_array[9], 29)
-
-        # still, normal sequence of length one behaviour:
-        self.failUnlessEqual(varsize_array[-1], 20)
-        self.failUnlessRaises(IndexError, lambda: varsize_array[-2])
-        # except for this one, which will raise MemoryError
-        self.failUnlessRaises(MemoryError, lambda: varsize_array[:])
-
-        # __setitem__
-        varsize_array[0] = 100
-        varsize_array[1] = 101
-        varsize_array[2] = 102
-        varsize_array[3] = 103
-        varsize_array[4] = 104
-        varsize_array[5] = 105
-        varsize_array[6] = 106
-        varsize_array[7] = 107
-        varsize_array[8] = 108
-        varsize_array[9] = 109
-
-        for i in range(10):
-            self.failUnlessEqual(varsize_array[i], i + 100)
-            self.failUnlessEqual(array[i], i + 100)
-
-        # __getslice__
-        self.failUnlessEqual(varsize_array[0:10], range(100, 110))
-        self.failUnlessEqual(varsize_array[1:9], range(101, 109))
-        self.failUnlessEqual(varsize_array[1:-1], [])
-
-        # __setslice__
-        varsize_array[0:10] = range(1000, 1010)
-        self.failUnlessEqual(varsize_array[0:10], range(1000, 1010))
-
-        varsize_array[1:9] = range(1001, 1009)
-        self.failUnlessEqual(varsize_array[1:9], range(1001, 1009))
-
-    def test_vararray_is_sane(self):
-        array = (c_int * 15)(20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
-
-        varsize_array = (c_int * 1).from_address(addressof(array))
-        varsize_array[:] = [1, 2, 3, 4, 5]
-
-        self.failUnlessEqual(array[:], [1, 2, 3, 4, 5, 25, 26, 27, 28, 29, 0, 0, 0, 0, 0])
-        self.failUnlessEqual(varsize_array[0:10], [1, 2, 3, 4, 5, 25, 26, 27, 28, 29])
-
-        array[:5] = [10, 11, 12, 13, 14]
-        self.failUnlessEqual(array[:], [10, 11, 12, 13, 14, 25, 26, 27, 28, 29, 0, 0, 0, 0, 0])
-        self.failUnlessEqual(varsize_array[0:10], [10, 11, 12, 13, 14, 25, 26, 27, 28, 29])
-
 if __name__ == "__main__":
     unittest.main()

Misc/NEWS

@@ -25,6 +25,10 @@ Library
 Extension Modules
 -----------------
 
+- Patch #1521817: Index range checking on ctypes arrays containing
+  exactly one element enabled again.  This allows iterating over these
+  arrays, without the need to check the array size before.
+
 - Bug #1521375: When the code in ctypes.util.find_library was
   run with root privileges, it could overwrite or delete
   /dev/null in certain cases; this is now fixed.

Modules/_ctypes/_ctypes.c

@@ -3573,7 +3573,8 @@ Array_item(PyObject *_self, Py_ssize_t index)
 	int offset, size;
 	StgDictObject *stgdict;
 
-	if (self->b_length == 0 || index < 0 || (self->b_length > 1 && index >= self->b_length)) {
+
+	if (index < 0 || index >= self->b_length) {
 		PyErr_SetString(PyExc_IndexError,
 				"invalid index");
 		return NULL;
@@ -3602,11 +3603,11 @@ Array_slice(PyObject *_self, Py_ssize_t ilow, Py_ssize_t ihigh)
 
 	if (ilow < 0)
 		ilow = 0;
-	else if (ilow > self->b_length && self->b_length != 1)
+	else if (ilow > self->b_length)
 		ilow = self->b_length;
 	if (ihigh < ilow)
 		ihigh = ilow;
-	else if (ihigh > self->b_length && self->b_length != 1)
+	else if (ihigh > self->b_length)
 		ihigh = self->b_length;
 	len = ihigh - ilow;
 
@@ -3649,8 +3650,7 @@ Array_ass_item(PyObject *_self, Py_ssize_t index, PyObject *value)
 	}
 	
 	stgdict = PyObject_stgdict((PyObject *)self);
-	if (self->b_length == 0 || index < 0
-	    || (self->b_length > 1 && index >= self->b_length)) {
+	if (index < 0 || index >= stgdict->length) {
 		PyErr_SetString(PyExc_IndexError,
 				"invalid index");
 		return -1;
@@ -3677,19 +3677,17 @@ Array_ass_slice(PyObject *_self, Py_ssize_t ilow, Py_ssize_t ihigh, PyObject *va
 
 	if (ilow < 0)
 		ilow = 0;
-	else if (ilow > self->b_length && self->b_length != 1)
+	else if (ilow > self->b_length)
 		ilow = self->b_length;
-
 	if (ihigh < 0)
 		ihigh = 0;
-
 	if (ihigh < ilow)
 		ihigh = ilow;
-	else if (ihigh > self->b_length && self->b_length != 1)
+	else if (ihigh > self->b_length)
 		ihigh = self->b_length;
 
 	len = PySequence_Length(value);
-	if (self->b_length != 1 && len != ihigh - ilow) {
+	if (len != ihigh - ilow) {
 		PyErr_SetString(PyExc_ValueError,
 				"Can only assign sequence of same size");
 		return -1;