   Weird problem with boost
  Today I (seemingly out of nowhere) started getting the following errors when compiling a few of my game classes:1>C:\libs\boost\boost/type_traits/is_polymorphic.hpp(46) : error C2504: 'Sketchy::BackgroundSprite' : base class undefinedThe output window gives me the following error:1>C:\libs\boost\boost/type_traits/is_polymorphic.hpp(46) : error C2504: 'Sketchy::BackgroundSprite' : base class undefined1>   C:\libs\boost\boost/type_traits/is_polymorphic.hpp(62) : see reference to class template instantiation 'boost::detail::is_polymorphic_imp1<T>::d2' being compiled1>   with1>   [1>  T=Sketchy::BackgroundSprite1>   ]It seems that it cannot find the base class of BackgroundSprite which is SceneObject. However, there a a lof of other classes that derive from SceneObject and they work just fine. Besides, I have not included is_polymorphic.hpp anywhere myself. I suppose another boost library has done that. For convenience, here is the header for BackgroundSprite:/** This file is part of Sketchy** Copyright (c) 2009 Sebastian Ahlman* http://www.sebastian-ahlman.fi/*/#ifndef _BACKGROUNDSPRITE_H_#define _BACKGROUNDSPRITE_H_#include <Ogre.h>#include <string>#include "Constants.h"#include "SceneObject.h"namespace Sketchy{// A non-physics background sprite. Belongs to either SKY, FAR_AWAY_BACKGROUND or NEAR_BACKGROUND.class BackgroundSprite : public SceneObject{public:void FrameStarted(const Ogre::FrameEvent& evt);void FrameEnded(const Ogre::FrameEvent& evt);void PhysicsStep();void CreateResources();void DestroyResources();BackgroundSprite(std::string name, std::string materialName, Ogre::Vector3 position, int type, float width, float height, Scene* scene);private:std::string m_Name;std::string m_MaterialName;Ogre::Vector3 m_Position;float m_Width, m_Height;};}#endif // _BACKGROUNDSPRITE_H_Any idea what might be wrong? Thanks!   
  It sounds like it's complaining about BackgroundSprite, not SceneObject.  Double check your #includes in whatever source file is being compiled when these errors pop up -- if BackgroundSprite.hpp is in there okay, things to double check for include:- All scopes properly closed (no missing }s, or ;s on the ends of classes)- You're not reusing #include guard names (often happens with copy+paste)Is this the entirety of your error messages?   ;  Okay, I got it working. Seems that it was somehow related to Box2D being compiled with static C++ runtimes, while the game uses dynamic ones. I am still not quite sure how this fixed the problem, but it is fixed now. Have to do some research on the subject later.Thanks for your help!   ;  Given that you were getting compile errors, and the runtime isn't even involved until link time, I find it unlikely that changing it is what fixed your problem.Good to hear it's fixed, though.   ;  Seemingly illogical "base class undefined" errors could also be a symptom of this problem.   