Minor modifications to issue #2613.

theano/sandbox/cuda/basic_ops.py

@@ -3044,21 +3044,25 @@ class GpuJoin(tensor.Join, GpuOp):
         as_tensor_variable_args = [as_cuda_ndarray_variable(x)
                                    for x in tensors]
 
-        # If axis is negative, we need to increment it with the number
-        # of dimensions of the smallest tensor variable
-        axis_int = int(axis.eval())
+        # Get joining axis as int
+        axis_int = 0
+        if not isinstance(axis, int):
+            try:
+                # Note : `get_scalar_constant_value` returns a ndarray not
+                # an int
+                axis_int = int(tensor.get_scalar_constant_value(axis))
+
+            except tensor.basic.NotScalarConstantError:
+                pass
+	else:
+	    axis_int = axis
+
         if (axis_int < 0):
             # Find tensor with smallest number of dimensions
             min_dim = -1
             for cnda in tensors:
-	        if min_dim < 0 or min_dim > len(list(cnda.shape)):
-	            min_dim = len(list(cnda.shape))
-
-	    # Throw error if it's not safe to increment axis with the 
-	    # minimum dim. Normally, this error will be caught in the 
-	    # Join op class, but just to be sure we double check it here. 
-            if axis_int + min_dim < 0:
-                raise ValueError("Cannot join list of tensors at axis (%s) when tensor with smallest dim (%s) is smaller." % (axis_int, min_dim))
+	        if min_dim < 0 or min_dim > cnda.ndim:
+	            min_dim = cnda.ndim
 
 	    axis = axis + min_dim