Fail fast on unsupported StridedMemoryView strides (#1730)

* Fail fast on unsupported StridedMemoryView strides.

Validate CAI and array-interface layout during StridedMemoryView construction so non-itemsize-divisible strides fail immediately. Add regression coverage to assert constructor-time failures for both interfaces.

Made-with: Cursor

* Expand CAI stride edge-case coverage for StridedMemoryView.

Add explicit CAI tests for zero, empty-array, and negative-stride layouts so stride divisibility validation remains covered for uncommon but valid cases. Require `shape` and `strides` as keyword-only args in the synthetic CAI helper to keep test call sites unambiguous.

Made-with: Cursor

Author: cpcloud

cuda_core/cuda/core/_memoryview.pyx

@@ -1096,6 +1096,8 @@ cpdef StridedMemoryView view_as_cai(obj, stream_ptr, view=None):
     buf.exporting_obj = obj
     buf.metadata = cai_data
     buf.dl_tensor = NULL
+    # Validate shape/strides/typestr eagerly so constructor paths fail fast.
+    buf.get_layout()
     buf.ptr, buf.readonly = cai_data["data"]
     buf.is_device_accessible = True
     if buf.ptr != 0:
@@ -1138,6 +1140,8 @@ cpdef StridedMemoryView view_as_array_interface(obj, view=None):
     buf.exporting_obj = obj
     buf.metadata = data
     buf.dl_tensor = NULL
+    # Validate shape/strides/typestr eagerly so constructor paths fail fast.
+    buf.get_layout()
     buf.ptr, buf.readonly = data["data"]
     buf.is_device_accessible = False
     buf.device_id = handle_return(driver.cuCtxGetDevice())

cuda_core/tests/test_utils.py

@@ -582,10 +582,53 @@ def test_from_array_interface_unsupported_strides(init_cuda):
     # Create an array with strides that aren't a multiple of itemsize
     x = np.array([(1, 2.0), (3, 4.0)], dtype=[("a", "i4"), ("b", "f8")])
     b = x["b"]
-    smv = StridedMemoryView.from_array_interface(b)
     with pytest.raises(ValueError, match="strides must be divisible by itemsize"):
-        # TODO: ideally this would raise on construction
-        smv.strides  # noqa: B018
+        StridedMemoryView.from_array_interface(b)
+
+
+def _make_cuda_array_interface_obj(*, shape, strides, typestr="<f8", data=(0, False), version=3):
+    return type(
+        "SyntheticCAI",
+        (),
+        {
+            "__cuda_array_interface__": {
+                "shape": shape,
+                "strides": strides,
+                "typestr": typestr,
+                "data": data,
+                "version": version,
+            }
+        },
+    )()
+
+
+def test_from_cuda_array_interface_unsupported_strides(init_cuda):
+    cai_obj = _make_cuda_array_interface_obj(shape=(2,), strides=(10,))
+    with pytest.raises(ValueError, match="strides must be divisible by itemsize"):
+        StridedMemoryView.from_cuda_array_interface(cai_obj, stream_ptr=-1)
+
+
+def test_from_cuda_array_interface_zero_strides(init_cuda):
+    cai_obj = _make_cuda_array_interface_obj(shape=(1, 1), strides=(0, 0))
+    smv = StridedMemoryView.from_cuda_array_interface(cai_obj, stream_ptr=-1)
+    assert smv.shape == (1, 1)
+    assert smv.strides == (0, 0)
+
+
+@pytest.mark.skipif(cp is None, reason="CuPy is not installed")
+def test_from_cuda_array_interface_negative_strides(init_cuda):
+    x = cp.arange(4, dtype=cp.float64)[::-1]
+    smv = StridedMemoryView.from_cuda_array_interface(_EnforceCAIView(x), stream_ptr=-1)
+    assert smv.shape == x.shape
+    assert smv.strides == (-1,)
+
+
+def test_from_cuda_array_interface_empty_array(init_cuda):
+    cai_obj = _make_cuda_array_interface_obj(shape=(0, 3), strides=(24, 8))
+    smv = StridedMemoryView.from_cuda_array_interface(cai_obj, stream_ptr=-1)
+    assert smv.size == 0
+    assert smv.shape == (0, 3)
+    assert smv.strides == (3, 1)
 
 
 @pytest.mark.parametrize(