C++ forward declaration error -

i have error goes this

    in file included level.hpp:12,                  main.cpp:4: corridor.hpp: in method `void game::corridor::update()': corridor.hpp:41: invalid use of undefined type `class game::level' corridor.hpp:13: forward declaration of `class game::level' corridor.hpp:42: invalid use of undefined type `class game::level' corridor.hpp:13: forward declaration of `class game::level' corridor.hpp:43: invalid use of undefined type `class game::level' corridor.hpp:13: forward declaration of `class game::level' corridor.hpp:44: invalid use of undefined type `class game::level' corridor.hpp:13: forward declaration of `class game::level' 

corridor , level ...

  // corridor.hpp  #ifndef game_corridor_hpp #define game_corridor_hpp  #include <moot/math.hpp>  //#include <level.hpp> #include <gamewindow.hpp>  namespace game {     class level; // <-- line 13      class corridor     {         static const unsigned int defaultleveldepth = 800;          moot::math::vector3d wp1, wp2, wp3, wp4;         moot::math::vector2d sp1, sp2, sp3, sp4;          level * p_level;      public:          corridor(moot::math::vector3d setfirstpoint, moot::math::vector3d setsecondpoint)          {             wp1 = setfirstpoint;             wp2 = setsecondpoint;              wp3 = setfirstpoint;             wp3.z += defaultleveldepth;              wp4 = setsecondpoint;             wp4.z += defaultleveldepth;         }           void update() {              sp1 = p_level->getlevelcamera().convert3dvectorwithscreenalgorithm(wp1); // <- line 41 etc.             sp2 = p_level->getlevelcamera().convert3dvectorwithscreenalgorithm(wp2);             sp3 = p_level->getlevelcamera().convert3dvectorwithscreenalgorithm(wp3);             sp4 = p_level->getlevelcamera().convert3dvectorwithscreenalgorithm(wp4);               //p_level->getlevelcamera();         }          void draw()//const         {             moot::color tempcolor;              windowinstance().graphics().drawquad( sp1.x, sp1.y, tempcolor,                                                                                 sp2.x,sp2.y, tempcolor,                                                                                 sp3.x, sp3.y, tempcolor,                                                                                 sp4.x,sp4.y, tempcolor, 1);         }           void setlevel(level* setlevel) {             p_level = setlevel;         }      }; }  #endif 

and

// level.hpp  #ifndef game_level_hpp #define game_level_hpp  #include <moot/forward.hpp> #include <moot/window.hpp> #include <moot/math.hpp>  #include <gamewindow.hpp> #include <camera.hpp> #include <corridor.hpp> #include <player.hpp>  #include <vector>   namespace game {     class level     {          typedef corridor* p_corridor;         typedef std::vector<p_corridor> corridorlist;         typedef corridorlist::reverse_iterator reversecorridoritter;          corridorlist m_map;         camera       m_camera;         player         m_player;       public:          level()         {             m_player.setlevel(this);              // lots of vertices being defined m_map.               // loop through , set camera             reversecorridoritter rit;              for(rit = m_map.rbegin(); rit != m_map.rend(); rit++)                 (*rit)->setlevel(this);           }           ~level()         {             reversecorridoritter rit;              for(rit = m_map.rbegin(); rit != m_map.rend(); rit++)                  delete (*rit);              m_map.clear();         }           void update()          {             // temp delete when input , player implimented.             if(pad[0].buttons & pad_up)                 m_camera.updatetargetoffsets(0, -2);              if(pad[0].buttons & pad_down)                 m_camera.updatetargetoffsets(0, 2);              if(pad[0].buttons & pad_left)                 m_camera.updatetargetoffsets(-2, 0);              if(pad[0].buttons & pad_right)                 m_camera.updatetargetoffsets(2, 0);              m_player.update();               reversecorridoritter rit;              (rit = m_map.rbegin(); rit != m_map.rend(); rit++)                 (*rit)->update();         }           void draw() // const // eh!!! wtf reverseiter isn't member         {             m_player.draw();               reversecorridoritter rit;              (rit = m_map.rbegin(); rit != m_map.rend(); rit++)                 (*rit)->draw();          }           camera& getlevelcamera() {             return m_camera;         }      }; }  #endif 

the pointer being set far can tell, when try access function level, boom!

thanks.

ps: compiler gcc 2.95.2 if makes difference.

edit

updated complete code.

you #include-ing level's complete declaration:

#include <level.hpp> 

...and then try forward-declare level:

namespace game {     class level; 

don't this. choose 1 or other. (edit) or @ least put forward-declaration before #include-ion of complete declaration. if you're doing in game_corridor.hpp setting pointers level, forward declare should fine. if need call functions on level within hpp file, you'll need #include complete declaration.

edit2:

based on clarifying edit op, must #include complete declaration of level, , not try use forward declaration.