Merge pull request #10529 from eric-wieser/fix-pep3118-error

BUG: Provide a better error message for out-of-order fields

2 files changed, 24 insertions, 5 deletions

diff --git a/numpy/core/src/multiarray/buffer.c b/numpy/core/src/multiarray/buffer.c
index e76d406de..f892cf6cd 100644
--- a/numpy/core/src/multiarray/buffer.c
+++ b/numpy/core/src/multiarray/buffer.c
@@ -12,6 +12,7 @@
 #include "npy_pycompat.h"
 
 #include "buffer.h"
+#include "common.h"
 #include "numpyos.h"
 #include "arrayobject.h"
 
@@ -243,14 +244,19 @@ _buffer_format_string(PyArray_Descr *descr, _tmp_string_t *str,
 
             child = (PyArray_Descr*)PyTuple_GetItem(item, 0);
             offset_obj = PyTuple_GetItem(item, 1);
-            new_offset = base_offset + PyInt_AsLong(offset_obj);
+            new_offset = PyInt_AsLong(offset_obj);
+            if (error_converting(new_offset)) {
+                return -1;
+            }
+            new_offset += base_offset;
 
             /* Insert padding manually */
             if (*offset > new_offset) {
-                PyErr_SetString(PyExc_RuntimeError,
-                                "This should never happen: Invalid offset in "
-                                "buffer format string generation. Please "
-                                "report a bug to the Numpy developers.");
+                PyErr_SetString(
+                    PyExc_ValueError,
+                    "dtypes with overlapping or out-of-order fields are not "
+                    "representable as buffers. Consider reordering the fields."
+                );
                 return -1;
             }
             while (*offset < new_offset) {
diff --git a/numpy/core/tests/test_multiarray.py b/numpy/core/tests/test_multiarray.py
index 0fbaacb03..d65bb17e6 100644
--- a/numpy/core/tests/test_multiarray.py
+++ b/numpy/core/tests/test_multiarray.py
@@ -6461,6 +6461,19 @@ class TestNewBufferProtocol(object):
             shape, strides = get_buffer_info(arr, ['C_CONTIGUOUS'])
             assert_(strides[-1] == 8)
 
+    def test_out_of_order_fields(self):
+        dt = np.dtype(dict(
+            formats=['<i4', '<i4'],
+            names=['one', 'two'],
+            offsets=[4, 0],
+            itemsize=8
+        ))
+
+        # overlapping fields cannot be represented by PEP3118
+        arr = np.empty(1, dt)
+        with assert_raises(ValueError):
+            memoryview(arr)
+
 
 class TestArrayAttributeDeletion(object):