Fix the code written while way too tired.

theano/gof/link.py

@@ -183,7 +183,7 @@ raise_with_op.print_thunk_trace = False
 class Linker(object):
     """WRITEME"""
 
-    def clone(allow_gc=undef):
+    def clone(self, allow_gc=undef):
         new = copy(self)
         if allow_gc is not undef:
             new.allow_gc = allow_gc

theano/scan_module/scan_op.py

@@ -38,9 +38,10 @@ _logger = logging.getLogger('theano.scan_module.scan_op')
 
 
 from theano.configparser import AddConfigVar, BoolParam
+
 AddConfigVar('scan.allow_gc',
-             "Allow/disallow gc inside of Scan",
-             BoolParam(False))
+             "Allow/disallow gc inside of Scan (default: config.allow_gc)",
+             BoolParam(lambda: config.allow_gc))
 
 
 class Scan(PureOp):
@@ -110,7 +111,7 @@ class Scan(PureOp):
             isinstance(mode_instance, compile.profilemode.ProfileMode)):
             mode_instance = compile.profilemode.ProfileMode(
                 optimizer=mode_instance.provided_optimizer,
-                linker=mode_instance.provided_linker)
+                linker=mode_instance.linker.clone(allow_gc=allow_gc))
             compile.profilemode.prof_mode_instance_to_print.append(
                                                     mode_instance)
             self.mode_instance = mode_instance
@@ -119,10 +120,9 @@ class Scan(PureOp):
             else:
                 self.mode_instance.message = "Scan sub profile"
         else:
-            mode_instance = mode_instance.__type__(
+            self.mode_instance = type(mode_instance)(
                 optimizer=mode_instance.provided_optimizer,
-                linker=mode_instance.provided_linker.clone(allow_gc=allow_gc))
-            self.mode_instance = mode_instance
+                linker=mode_instance.linker.clone(allow_gc=allow_gc))
 
         if not hasattr(self, 'name') or self.name is None:
             self.name = 'scan_fn'
@@ -632,10 +632,17 @@ class Scan(PureOp):
             p = self.execute
         # default arguments are stored in the closure of `rval`
 
-        def rval(p=p, i=node_input_storage, o=node_output_storage, n=node):
+        # Big ugly hack since we can't get the real value of allow_gc
+        # for the englobing function.
+        allow_gc = config.allow_gc
+
+        def rval(p=p, i=node_input_storage, o=node_output_storage, n=node,
+                 allow_gc=allow_gc):
             r = p(n, [x[0] for x in i], o)
             for o in node.outputs:
                 compute_map[o][0] = True
+            if allow_gc:
+                self.fn.free()
             return r
         rval.inputs = node_input_storage
         rval.outputs = node_output_storage