BUG: Remove fragile use of __array_interface__ in ctypeslib.as_array

Everything behaves a lot better if we let the array constructor handle it, which will use the ctypes PEP3118 support.

Bugs this fixes:

* Stale state being attached to pointer objects (fixes gh-2671, closes gh-6214)
* Weird failure modes on structured arrays (fixes-10978)
* A regression in gh-10882 (fixes gh-10968)

1 files changed, 43 insertions, 5 deletions

diff --git a/numpy/tests/test_ctypeslib.py b/numpy/tests/test_ctypeslib.py
index fd4336fad..75ce9c8ca 100644
--- a/numpy/tests/test_ctypeslib.py
+++ b/numpy/tests/test_ctypeslib.py
@@ -118,17 +118,55 @@ class TestNdpointer(object):
 class TestAsArray(object):
     def test_array(self):
         from ctypes import c_int
-        at = c_int * 2
-        a = as_array(at(1, 2))
+
+        pair_t = c_int * 2
+        a = as_array(pair_t(1, 2))
         assert_equal(a.shape, (2,))
         assert_array_equal(a, np.array([1, 2]))
-        a = as_array((at * 3)(at(1, 2), at(3, 4), at(5, 6)))
+        a = as_array((pair_t * 3)(pair_t(1, 2), pair_t(3, 4), pair_t(5, 6)))
         assert_equal(a.shape, (3, 2))
         assert_array_equal(a, np.array([[1, 2], [3, 4], [5, 6]]))
 
     def test_pointer(self):
         from ctypes import c_int, cast, POINTER
+
         p = cast((c_int * 10)(*range(10)), POINTER(c_int))
-        a = as_array(p, (10,))
+
+        a = as_array(p, shape=(10,))
         assert_equal(a.shape, (10,))
-        assert_array_equal(a, np.array(range(10)))
+        assert_array_equal(a, np.arange(10))
+
+        a = as_array(p, shape=(2, 5))
+        assert_equal(a.shape, (2, 5))
+        assert_array_equal(a, np.arange(10).reshape((2, 5)))
+
+        # shape argument is required
+        assert_raises(TypeError, as_array, p)
+
+    def test_struct_array_pointer(self):
+        from ctypes import c_int16, Structure, pointer
+
+        class Struct(Structure):
+            _fields_ = [('a', c_int16)]
+
+        Struct3 = 3 * Struct
+
+        c_array = (2 * Struct3)(
+            Struct3(Struct(a=1), Struct(a=2), Struct(a=3)),
+            Struct3(Struct(a=4), Struct(a=5), Struct(a=6))
+        )
+
+        expected = np.array([
+            [(1,), (2,), (3,)],
+            [(4,), (5,), (6,)],
+        ], dtype=[('a', np.int16)])
+
+        def check(x):
+            assert_equal(x.dtype, expected.dtype)
+            assert_equal(x, expected)
+
+        # all of these should be equivalent
+        check(as_array(c_array))
+        check(as_array(pointer(c_array), shape=()))
+        check(as_array(pointer(c_array[0]), shape=(2,)))
+        check(as_array(pointer(c_array[0][0]), shape=(2, 3)))