outputgruard check added to debugmode

theano/compile/debugmode.py

@@ -27,7 +27,8 @@ from theano.compile.function_module import (
     FunctionMaker, Function, infer_reuse_pattern,
     SymbolicOutput, Supervisor, std_fgraph)
 from theano.compile.mode import Mode, register_mode
-from theano.compile.ops import OutputGuard
+from theano.compile.ops import OutputGuard, _output_guard
+
 
 __docformat__ = "restructuredtext en"
 _logger = logging.getLogger("theano.compile.debugmode")
@@ -2311,6 +2312,17 @@ class _Maker(FunctionMaker):  # inheritance buys a few helper functions
                               "of", len(li), "events was stable.",
                               file=sys.stderr)
         self.fgraph = fgraph
+        for o in fgraph.outputs:
+            try:
+                fgraph.replace_validate(o, _output_guard(o), reason='output_guard')
+                raise Exception("Output variable %s required output_guard, "
+                                "how was this output left unprotected against "
+                                "destructive operations?" % o)
+
+            except gof.InconsistencyError:
+                # This output is already impossible to destroy.
+                # No guard necessary
+                pass
 
         linker = _Linker(self)
 

theano/compile/mode.py

@@ -118,9 +118,9 @@ class AddDestroyHandler(gof.Optimizer):
                 supervisor_added = True
                 break
         if not supervisor_added:
-            warnings.warn("WARNING: Supervisor is not added. Please do not"
-                          "use some_op.optimize(fgraph). Instead use theano.function"
-                          "to add the optimiztions.",
+            warnings.warn("WARNING: Supervisor is not added. Please build a FunctionGraph"
+                          "via theano.compile.function_module.std_graph()"
+                          "or add the Supervisor class manually.",
                           stacklevel=3)
 
     def add_requirements(self, fgraph):