If DebugMode receive a specific linker, raise an error at it can only use its own linker.

theano/compile/debugmode.py

@@ -1674,6 +1674,9 @@ class DebugMode(Mode):
         If any of these arguments (except optimizer) is not None, it overrides the class default.
         The linker arguments is not used. It is set their to allow Mode.requiring() and some other fct to work with DebugMode too.
         """
+        if linker is not None and not isinstance(linker,_Linker):
+            raise Exception("DebugMode can use only its own linker! Don't give him one to use it.")
+
         super(DebugMode, self).__init__(
                 optimizer=optimizer,
                 linker=_Linker)

theano/compile/mode.py

@@ -285,9 +285,12 @@ def get_mode(orig_string):
         if instanciated_default_mode:
             return instanciated_default_mode
         #need to import later to break circular dependency.
-        from profilemode import ProfileMode,prof_mode_instance_to_print
+        if string == 'DebugMode':
             from debugmode import DebugMode
-
+            #DebugMode use its own linker.
+            ret = eval(string+'(optimizer=config.optimizer)')
+        else:
+            from profilemode import ProfileMode,prof_mode_instance_to_print
             ret = eval(string+'(linker=config.linker, optimizer=config.optimizer)')
 
     elif not predefined_modes.has_key(string):

theano/configdefaults.py

@@ -49,13 +49,12 @@ try:
     subprocess.Popen('gcc', stdout=subprocess.PIPE, stderr=subprocess.PIPE)
     # Keep the default linker the same as the one for the mode FAST_RUN
     AddConfigVar('linker',
-            "Default linker. If not None, will use this linker with the Mode "+
-            "object(not ProfileMode or DebugMode)",
+                 "Default linker used if the theano flags mode is Mode or ProfileMode",
                  EnumStr('c|py', 'py', 'c', 'c|py_nogc', 'c&py'))
 except OSError:
     # gcc is not present, linker should default to python only
     AddConfigVar('linker',
-            "Default linker. If not None, will use this linker with the Mode object(not ProfileMode or DebugMode)",
+                 "Default linker used if the theano flags mode is Mode or ProfileMode",
                  EnumStr('py', 'c|py', 'c', 'c|py_nogc', 'c&py'))
     warning('GCC not detected ! Theano will be unable to execute optimized '+
             'C-implementations (for both CPU and GPU) and will default to '+