fix ce bug in label value, test=develop

python/paddle/fluid/tests/unittests/test_cross_entropy_loss.py

@@ -1363,5 +1363,19 @@ class CrossEntropyLoss(unittest.TestCase):
         self.assertTrue(np.allclose(dy_ret_value, expected))
 
 
+class TestCrossEntropyFAPIError(unittest.TestCase):
+    def test_errors(self):
+        with program_guard(Program(), Program()):
+
+            def test_LabelValue():
+                input_data = paddle.rand(shape=[20, 100])
+                label_data = paddle.randint(0, 100, shape=[5, 1], dtype="int64")
+                label_data[0] = 255
+                paddle.nn.functional.cross_entropy(
+                    input=input_data, label=label_data)
+
+            self.assertRaises(ValueError, test_LabelValue)
+
+
 if __name__ == "__main__":
     unittest.main()

python/paddle/nn/functional/loss.py

@@ -1411,6 +1411,11 @@ def cross_entropy(input,
                 out = core.ops.elementwise_mul(out, weight_gather_reshape)
 
             else:
+                for label_val in label:
+                    if label_val < 0 or label_val >= input.shape[-1]:
+                        raise ValueError(
+                            'Expected 0 <= label_value < class_dimension({}), but got label_value {}'.
+                            format(input.shape[-1], label_val.numpy()))
                 weight_gather = core.ops.gather_nd(weight, label)
                 input_shape = list(label.shape)
                 weight_gather_reshape = reshape(