In get_scalar_constant_value, do not return internal memory of constant

theano/tensor/basic.py

@@ -612,14 +612,14 @@ def get_scalar_constant_value(orig_v, elemwise=True,
             return numpy.asarray(v)
 
         if isinstance(v, numpy.ndarray):
-            return numpy_scalar(v)
+            return numpy_scalar(v).copy()
 
         if isinstance(v, Constant):
             if getattr(v.tag, 'unique_value', None) is not None:
                 data = v.tag.unique_value
             else:
                 data = v.data
-            return numpy_scalar(data)
+            return numpy_scalar(data).copy()
 
         if not only_process_constants and getattr(v, 'owner', None):
             if isinstance(v.owner.op, (Alloc, DimShuffle, Rebroadcast,
@@ -649,7 +649,7 @@ def get_scalar_constant_value(orig_v, elemwise=True,
                              for i in v.owner.inputs]
                     ret = [[None]]
                     v.owner.op.perform(v.owner, const, ret)
-                    return ret[0][0]
+                    return ret[0][0].copy()
             elif elemwise and isinstance(v.owner.op, Elemwise):
                 if isinstance(v.owner.op.scalar_op, scal.Second):
                     # We don't need both input to be constant for second
@@ -662,13 +662,13 @@ def get_scalar_constant_value(orig_v, elemwise=True,
                              for i in v.owner.inputs]
                     ret = [[None]]
                     v.owner.op.perform(v.owner, const, ret)
-                    return ret[0][0]
+                    return ret[0][0].copy()
             elif (isinstance(v.owner.op, theano.tensor.subtensor.Subtensor) and
                   v.ndim == 0):
                 if isinstance(v.owner.inputs[0], TensorConstant):
                     cdata = tuple(v.owner.op.get_constant_idx(v.owner.inputs))
                     try:
-                        return v.owner.inputs[0].data.__getitem__(cdata)
+                        return v.owner.inputs[0].data.__getitem__(cdata).copy()
                     except IndexError:
                         raise IndexError(
                             str(tuple(v.owner.op.idx_list)) +

theano/tensor/tests/test_basic.py

@@ -48,7 +48,7 @@ from theano.tensor import (_shared, wvector, bvector, autocast_float_as,
         nonzero, flatnonzero, nonzero_values,
         stacklists, DimShuffle, hessian, ptp, power,
         swapaxes, choose, Choose, NoneConst, AllocEmpty,
-        isclose, allclose, mgrid, ogrid,
+        isclose, allclose, mgrid, ogrid, extract_constant,
         )
 
 from theano.tests import unittest_tools as utt
@@ -7026,12 +7026,21 @@ class T_get_scalar_constant_value(unittest.TestCase):
         s = theano.tensor.second(shp, c)
         assert get_scalar_constant_value(s) == c.data
 
+    def test_copy(self):
+        # Make sure we do not return the internal storage of a constant,
+        # so we cannot change the value of a constant by mistake.
+        c = theano.tensor.constant(3)
+        d = extract_constant(c)
+        d += 1
+        e = extract_constant(c)
+        self.assertTrue(e == 3, (c, d, e))
+
 
 class T_as_tensor_variable(unittest.TestCase):
     """
     We test that ticket #649 stay fixed.
     We should not allow as_tensor_variable to accept True or False
-    But it should upcast an ndrarray of bool to uint8
+    But it should upcast an ndarray of bool to uint8
     """
 
     def test_bool(self):