From dd8a2a8e29b0dc85dca4d2964c92df3604acc212 Mon Sep 17 00:00:00 2001
From: Eric Wieser <wieser.eric@gmail.com>
Date: Fri, 12 Jan 2018 10:03:48 -0800
Subject: [PATCH] BUG: Instead of returning garbage, make dtype.descr error for
 out-of-order fields

---
 numpy/core/_internal.py          |  4 ++++
 numpy/core/tests/test_records.py | 13 +++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/numpy/core/_internal.py b/numpy/core/_internal.py
index 004c2762b55e..8c6596d131ca 100644
--- a/numpy/core/_internal.py
+++ b/numpy/core/_internal.py
@@ -110,6 +110,10 @@ def _array_descr(descriptor):
             num = field[1] - offset
             result.append(('', '|V%d' % num))
             offset += num
+        elif field[1] < offset:
+            raise ValueError(
+                "dtype.descr is not defined for types with overlapping or "
+                "out-of-order fields")
         if len(field) > 3:
             name = (field[2], field[3])
         else:
diff --git a/numpy/core/tests/test_records.py b/numpy/core/tests/test_records.py
index 73cfe35701bc..9461bddc27b4 100644
--- a/numpy/core/tests/test_records.py
+++ b/numpy/core/tests/test_records.py
@@ -340,6 +340,19 @@ def test_nonwriteable_setfield(self):
         with assert_raises(ValueError):
             r.setfield([2,3], *r.dtype.fields['f'])
 
+    def test_out_of_order_fields(self):
+        # names in the same order, padding added to descr
+        x = self.data[['col1', 'col2']]
+        assert_equal(x.dtype.names, ('col1', 'col2'))
+        assert_equal(x.dtype.descr,
+                     [('col1', '<i4'), ('col2', '<i4'), ('', '|V4')])
+
+        # names change order to match indexing, as of 1.14 - descr can't
+        # represent that
+        y = self.data[['col2', 'col1']]
+        assert_equal(y.dtype.names, ('col2', 'col1'))
+        assert_raises(ValueError, lambda: y.dtype.descr)
+
     def test_pickle_1(self):
         # Issue #1529
         a = np.array([(1, [])], dtype=[('a', np.int32), ('b', np.int32, 0)])