sim: Include object header files in SWIG interfaces

When casting objects in the generated SWIG interfaces, SWIG uses
classical C-style casts ( (Foo *)bar; ). In some cases, this can
degenerate into the equivalent of a reinterpret_cast (mainly if only a
forward declaration of the type is available). This usually works for
most compilers, but it is known to break if multiple inheritance is
used anywhere in the object hierarchy.

This patch introduces the cxx_header attribute to Python SimObject
definitions, which should be used to specify a header to include in
the SWIG interface. The header should include the declaration of the
wrapped object. We currently don't enforce header the use of the
header attribute, but a warning will be generated for objects that do
not use it.

src/python/m5/SimObject.py

@@ -105,6 +105,9 @@ allClasses = {}
 # dict to look up SimObjects based on path
 instanceDict = {}
 
+# Did any of the SimObjects lack a header file?
+noCxxHeader = False
+
 def public_value(key, value):
     return key.startswith('_') or \
                isinstance(value, (FunctionType, MethodType, ModuleType,
@@ -119,6 +122,7 @@ class MetaSimObject(type):
     init_keywords = { 'abstract' : bool,
                       'cxx_class' : str,
                       'cxx_type' : str,
+                      'cxx_header' : str,
                       'type' : str }
     # Attributes that can be set any time
     keywords = { 'check' : FunctionType }
@@ -203,6 +207,12 @@ class MetaSimObject(type):
 
             cls._value_dict['cxx_type'] = '%s *' % cls._value_dict['cxx_class']
 
+            if 'cxx_header' not in cls._value_dict:
+                global noCxxHeader
+                noCxxHeader = True
+                print >> sys.stderr, \
+                    "warning: No header file specified for SimObject: %s" % name
+
         # Export methods are automatically inherited via C++, so we
         # don't want the method declarations to get inherited on the
         # python side (and thus end up getting repeated in the wrapped
@@ -407,6 +417,7 @@ class MetaSimObject(type):
         code('#include "params/$cls.hh"')
         for param in params:
             param.cxx_predecls(code)
+        code('#include "${{cls.cxx_header}}"')
         cls.export_method_cxx_predecls(code)
         code('''\
 /**
@@ -568,15 +579,7 @@ class SimObject(object):
     __metaclass__ = MetaSimObject
     type = 'SimObject'
     abstract = True
-
-    @classmethod
-    def export_method_cxx_predecls(cls, code):
-        code('''
-#include <Python.h>
-
-#include "sim/serialize.hh"
-#include "sim/sim_object.hh"
-''')
+    cxx_header = "sim/sim_object.hh"
 
     @classmethod
     def export_method_swig_predecls(cls, code):
@@ -1099,10 +1102,11 @@ baseClasses = allClasses.copy()
 baseInstances = instanceDict.copy()
 
 def clear():
-    global allClasses, instanceDict
+    global allClasses, instanceDict, noCxxHeader
 
     allClasses = baseClasses.copy()
     instanceDict = baseInstances.copy()
+    noCxxHeader = False
 
 # __all__ defines the list of symbols that get exported when
 # 'from config import *' is invoked.  Try to keep this reasonably