From f30cecb89264660b5818fedaf7ce1fbb3e35050b Mon Sep 17 00:00:00 2001
From: Alexander Belopolsky <a@enlnt.com>
Date: Wed, 6 Nov 2013 14:17:27 -0500
Subject: BUG: Support ndim=0 when constructing arrays from buffer

Previously the buffer was interpreted as 1-dimensional when
no shape was provided, even when ndim was 0.

Closes gh-4015
---
 numpy/core/src/multiarray/ctors.c   | 18 +++++++++++++-----
 numpy/core/tests/test_multiarray.py |  8 ++++++++
 2 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/numpy/core/src/multiarray/ctors.c b/numpy/core/src/multiarray/ctors.c
index 1b7e1c428..a897169a3 100644
--- a/numpy/core/src/multiarray/ctors.c
+++ b/numpy/core/src/multiarray/ctors.c
@@ -1293,8 +1293,8 @@ _array_from_buffer_3118(PyObject *obj, PyObject **out)
         descr->elsize = view->itemsize;
     }
 
+    nd = view->ndim;
     if (view->shape != NULL) {
-        nd = view->ndim;
         if (nd >= NPY_MAXDIMS || nd < 0) {
             goto fail;
         }
@@ -1318,9 +1318,17 @@ _array_from_buffer_3118(PyObject *obj, PyObject **out)
         }
     }
     else {
-        nd = 1;
-        shape[0] = view->len / view->itemsize;
-        strides[0] = view->itemsize;
+        if (nd == 1) {
+            shape[0] = view->len / view->itemsize;
+            strides[0] = view->itemsize;
+        }
+        else if (nd > 1) {
+            PyErr_WarnEx(PyExc_RuntimeWarning,
+                         "ndim computed from the PEP 3118 buffer format "
+                         "is greater than 1, but shape is NULL.",
+                         0);
+            goto fail;
+        }
     }
 
     flags = NPY_ARRAY_BEHAVED & (view->readonly ? ~NPY_ARRAY_WRITEABLE : ~0);
@@ -2082,7 +2090,7 @@ PyArray_FromInterface(PyObject *origin)
     /* Get the strides */
 
     iface = PyArray_GetAttrString_SuppressException(origin,
-						    "__array_interface__");
+                                                    "__array_interface__");
     if (iface == NULL) {
         return Py_NotImplemented;
     }
diff --git a/numpy/core/tests/test_multiarray.py b/numpy/core/tests/test_multiarray.py
index 9d191da35..f42c426bc 100644
--- a/numpy/core/tests/test_multiarray.py
+++ b/numpy/core/tests/test_multiarray.py
@@ -3407,9 +3407,13 @@ class TestNewBufferProtocol(object):
         y2 = np.array(x)
         assert_(not y.flags.owndata)
         assert_(y2.flags.owndata)
+
         assert_equal(y.dtype, obj.dtype)
+        assert_equal(y.shape, obj.shape)
         assert_array_equal(obj, y)
+
         assert_equal(y2.dtype, obj.dtype)
+        assert_equal(y2.shape, obj.shape)
         assert_array_equal(obj, y2)
 
     def test_roundtrip(self):
@@ -3520,6 +3524,10 @@ class TestNewBufferProtocol(object):
                 x = np.zeros(4, dtype=dt)
                 self._check_roundtrip(x)
 
+    def test_roundtrip_scalar(self):
+        # Issue #4015.
+        self._check_roundtrip(0)
+
     def test_export_simple_1d(self):
         x = np.array([1, 2, 3, 4, 5], dtype='i')
         y = memoryview(x)
-- 
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