BUG: Fix for np.dtype(ctypes.Structure) does not respect _pack_ field

See #10532
Cosmetic changes + added an additional test with a more complex
structure.

1 files changed, 20 insertions, 0 deletions

diff --git a/numpy/core/tests/test_dtype.py b/numpy/core/tests/test_dtype.py
index f4b118bab..39493d52d 100644
--- a/numpy/core/tests/test_dtype.py
+++ b/numpy/core/tests/test_dtype.py
@@ -837,6 +837,26 @@ class TestFromCTypes(object):
         ])
         self.check(PackedStructure, expected)
 
+    def test_large_packed_structure(self):
+        class PackedStructure(ctypes.Structure):
+            _pack_ = 2
+            _fields_ = [
+                ('a', ctypes.c_uint8),
+                ('b', ctypes.c_uint16),
+                ('c', ctypes.c_uint8),
+                ('d', ctypes.c_uint16),
+                ('e', ctypes.c_uint32),
+                ('f', ctypes.c_uint32),
+                ('g', ctypes.c_uint8)
+            ]
+        expected = np.dtype(dict(
+            formats=[np.uint8, np.uint16, np.uint8, np.uint16, np.uint32, np.uint32, np.uint8 ],
+            offsets=[0, 2, 4, 6, 8, 12, 16],
+            names=['a', 'b', 'c', 'd', 'e', 'f', 'g'],
+            itemsize=18
+        ))
+        self.check(PackedStructure, expected)
+
     @pytest.mark.xfail(sys.byteorder != 'little',
         reason="non-native endianness does not work - see gh-10533")
     def test_little_endian_structure(self):