numpy · charris · Jul 22, 2025 · Jul 11, 2025
diff --git a/numpy/_core/src/umath/ufunc_object.c b/numpy/_core/src/umath/ufunc_object.c
@@ -3727,6 +3727,8 @@ PyUFunc_GenericReduction(PyUFuncObject *ufunc,
     if (ret == NULL) {
         goto fail;
     }
+
+    Py_XDECREF(out);
 
     Py_DECREF(signature[0]);
     Py_DECREF(signature[1]);
@@ -3753,6 +3755,8 @@ PyUFunc_GenericReduction(PyUFuncObject *ufunc,
     return wrapped_result;
 
 fail:
+    Py_XDECREF(out);
+
     Py_XDECREF(signature[0]);
     Py_XDECREF(signature[1]);
     Py_XDECREF(signature[2]);

diff --git a/numpy/_core/tests/test_ufunc.py b/numpy/_core/tests/test_ufunc.py
@@ -3004,6 +3004,45 @@ def test_reduce_casterrors(offset):
     assert out[()] < value * offset
 
 
+@pytest.mark.skipif(not HAS_REFCOUNT, reason="Python lacks refcounts")
+def test_reduction_no_reference_leak():
+    # Test that the generic reduction does not leak references.
+    # gh-29358
+    arr = np.array([1, 2, 3], dtype=np.int32)
+    count = sys.getrefcount(arr)
+
+    np.add.reduce(arr, dtype=np.int32, initial=0)
+    assert count == sys.getrefcount(arr)
+
+    np.add.accumulate(arr, dtype=np.int32)
+    assert count == sys.getrefcount(arr)
+
+    np.add.reduceat(arr, [0, 1], dtype=np.int32)
+    assert count == sys.getrefcount(arr)
+
+    # with `out=` the reference count is not changed
+    out = np.empty((), dtype=np.int32)
+    out_count = sys.getrefcount(out)
+
+    np.add.reduce(arr, dtype=np.int32, out=out, initial=0)
+    assert count == sys.getrefcount(arr)
+    assert out_count == sys.getrefcount(out)
+
+    out = np.empty(arr.shape, dtype=np.int32)
+    out_count = sys.getrefcount(out)
+
+    np.add.accumulate(arr, dtype=np.int32, out=out)
+    assert count == sys.getrefcount(arr)
+    assert out_count == sys.getrefcount(out)
+
+    out = np.empty((2,), dtype=np.int32)
+    out_count = sys.getrefcount(out)
+
+    np.add.reduceat(arr, [0, 1], dtype=np.int32, out=out)
+    assert count == sys.getrefcount(arr)
+    assert out_count == sys.getrefcount(out)
+
+
 def test_object_reduce_cleanup_on_failure():
     # Test cleanup, including of the initial value (manually provided or not)
     with pytest.raises(TypeError):