blender -P xxx -b crashed sometimes, still will crash in some cases if the python functions access screen data. but at least Blender.sys.expandpath wont segfault anymore.

source/blender/python/api2_2x/Blender.c

@@ -817,7 +817,8 @@ void M_Blender_Init(void)
 	G.scene is NULL */
 	if(G.background && G.main->scene.first==0) {
 		Scene *sce= add_scene("1");
-		set_scene(sce);
+		//set_scene(sce); /* causes a crash */
+		G.scene= sce;
 	}
 	
 	module = Py_InitModule3("Blender", Blender_methods,

source/blender/src/drawscene.c

@@ -134,10 +134,8 @@ void set_scene(Scene *sce)		/* also see scene.c: set_scene_bg() */
 	set_radglobal();
 		
 	/* complete redraw */
-	if (!G.background) {
 	allqueue(REDRAWALL, 0);
 	allqueue(REDRAWDATASELECT, 0);	/* does a remake */
-	}
 }