BUG: ensure passing np.dtype to itself doesn't crash

ngoldbaum · ngoldbaum · commit ac8f1f1027ff · 2023-10-31T10:06:01.000-06:00
diff --git a/numpy/_core/src/multiarray/convert_datatype.c b/numpy/_core/src/multiarray/convert_datatype.c
@@ -1099,6 +1099,9 @@ PyArray_CastDescrToDType(PyArray_Descr *descr, PyArray_DTypeMeta *given_DType)
         Py_INCREF(descr);
         return descr;
     }
+    if (given_DType == (PyArray_DTypeMeta *)&PyArrayDescr_Type) {
+        goto error;
+    }
     if (!NPY_DT_is_parametric(given_DType)) {
         /*
          * Don't actually do anything, the default is always the result
diff --git a/numpy/_core/tests/test_dtype.py b/numpy/_core/tests/test_dtype.py
@@ -1931,3 +1931,9 @@ def test_result_type_integers_and_unitless_timedelta64():
     td = np.timedelta64(4)
     result = np.result_type(0, td)
     assert_dtype_equal(result, td.dtype)
+
+
+def test_creating_dtype_with_dtype_class_errors():
+    # Regression test for #25031, calling `np.dtype` with itself segfaulted.
+    with pytest.raises(TypeError, match="float64 to <class 'numpy.dtype'>"):
+        np.array(np.ones(10), dtype=np.dtype)
