title: Linker errors between multiple projects in Visual C++
body: <p>I have a solution with multiple projects. I have a "main" project, which acts as a menu and from there, the user can access any of the other projects. On this main project, I get linker errors for every function called. How do I avoid these linker errors? I set the project dependencies already in the "Project Dependencies..." dialog.</p>
  
  <p>Thanks</p>
  
  <p><strong>EDIT -- I did as suggested and added the output folder to the linker's additional directories. Now, however, I get a million errors as follows:</strong></p>
  
  <pre><code>3>msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: void __thiscall std::basic_ios >::setstate(int,bool)" (?setstate@?$basic_ios@DU?$char_traits@D@std@@@std@@QAEXH_N@Z) already defined in panels.lib(panel_main.obj)
  3>msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: int __thiscall std::ios_base::width(int)" (?width@ios_base@std@@QAEHH@Z) already defined in panels.lib(panel_main.obj)
  3>msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: int __thiscall std::basic_streambuf >::sputn(char const *,int)" (?sputn@?$basic_streambuf@DU?$char_traits@D@std@@@std@@QAEHPBDH@Z) already defined in panels.lib(panel_main.obj)
  3>msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: static bool __cdecl std::char_traits::eq_int_type(int const &,int const &)" (?eq_int_type@?$char_traits@D@std@@SA_NABH0@Z) already defined in panels.lib(panel_main.obj)
  3>msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: static int __cdecl std::char_traits::eof(void)" (?eof@?$char_traits@D@std@@SAHXZ) already defined in panels.lib(panel_main.obj)
  3>msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: int __thiscall std::basic_streambuf >::sputc(char)" (?sputc@?$basic_streambuf@DU?$char_traits@D@std@@@std@@QAEHD@Z) already defined in panels.lib(panel_main.obj)
  3>msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: class std::basic_streambuf > * __thiscall std::basic_ios >::rdbuf(void)const " (?rdbuf@?$basic_ios@DU?$char_traits@D@std@@@std@@QBEPAV?$basic_streambuf@DU?$char_traits@D@std@@@2@XZ) already defined in panels.lib(panel_main.obj)
  3>msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: char __thiscall std::basic_ios >::fill(void)const " (?fill@?$basic_ios@DU?$char_traits@D@std@@@std@@QBEDXZ) already defined in panels.lib(panel_main.obj)
  3>msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: int __thiscall std::ios_base::flags(void)const " (?flags@ios_base@std@@QBEHXZ) already defined in panels.lib(panel_main.obj)
  3>msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: int __thiscall std::ios_base::width(void)const " (?width@ios_base@std@@QBEHXZ) already defined in panels.lib(panel_main.obj)
  3>msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: static unsigned int __cdecl std::char_traits::length(char const *)" (?length@?$char_traits@D@std@@SAIPBD@Z) already defined in panels.lib(panel_main.obj)
  3>msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: class std::basic_ostream > & __thiscall std::basic_ostream >::flush(void)" (?flush@?$basic_ostream@DU?$char_traits@D@std@@@std@@QAEAAV12@XZ) already defined in panels.lib(panel_main.obj)
  3>msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: class std::basic_ostream > * __thiscall std::basic_ios >::tie(void)const " (?tie@?$basic_ios@DU?$char_traits@D@std@@@std@@QBEPAV?$basic_ostream@DU?$char_traits@D@std@@@2@XZ) already defined in panels.lib(panel_main.obj)
  3>msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: bool __thiscall std::ios_base::good(void)const " (?good@ios_base@std@@QBE_NXZ) already defined in panels.lib(panel_main.obj)
  3>msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: void __thiscall std::basic_ostream >::_Osfx(void)" (?_Osfx@?$basic_ostream@DU?$char_traits@D@std@@@std@@QAEXXZ) already defined in panels.lib(panel_main.obj)
  3>msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: void __thiscall std::basic_streambuf >::_Lock(void)" (?_Lock@?$basic_streambuf@DU?$char_traits@D@std@@@std@@QAEXXZ) already defined in panels.lib(panel_main.obj)
  3>msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: void __thiscall std::basic_streambuf >::_Unlock(void)" (?_Unlock@?$basic_streambuf@DU?$char_traits@D@std@@@std@@QAEXXZ) already defined in panels.lib(panel_main.obj)
  3>msvcprtd.lib(MSVCP90D.dll) : error LNK2005: "public: class std::locale::facet * __thiscall std::locale::facet::_Decref(void)" (?_Decref@facet@locale@std@@QAEPAV123@XZ) already defined in panels.lib(panel_main.obj)
  3>libcpmtd.lib(ios.obj) : error LNK2005: "private: static void __cdecl std::ios_base::_Ios_base_dtor(class std::ios_base *)" (?_Ios_base_dtor@ios_base@std@@CAXPAV12@@Z) already defined in msvcprtd.lib(MSVCP90D.dll)
  3>libcpmtd.lib(ios.obj) : error LNK2005: "public: static void __cdecl std::ios_base::_Addstd(class std::ios_base *)" (?_Addstd@ios_base@std@@SAXPAV12@@Z) already defined in msvcprtd.lib(MSVCP90D.dll)
  3>libcpmtd.lib(locale0.obj) : error LNK2005: "void __cdecl _AtModuleExit(void (__cdecl*)(void))" (?_AtModuleExit@@YAXP6AXXZ@Z) already defined in msvcprtd.lib(locale0_implib.obj)
  3>libcpmtd.lib(locale0.obj) : error LNK2005: __Fac_tidy already defined in msvcprtd.lib(locale0_implib.obj)
  3>libcpmtd.lib(locale0.obj) : error LNK2005: "private: static void __cdecl std::locale::facet::facet_Register(class std::locale::facet *)" (?facet_Register@facet@locale@std@@CAXPAV123@@Z) already defined in msvcprtd.lib(locale0_implib.obj)
  3>libcpmtd.lib(locale0.obj) : error LNK2005: "private: static class std::locale::_Locimp * __cdecl std::locale::_Getgloballocale(void)" (?_Getgloballocale@locale@std@@CAPAV_Locimp@12@XZ) already defined in msvcprtd.lib(MSVCP90D.dll)
  3>libcpmtd.lib(locale0.obj) : error LNK2005: "private: static class std::locale::_Locimp * __cdecl std::locale::_Init(void)" (?_Init@locale@std@@CAPAV_Locimp@12@XZ) already defined in msvcprtd.lib(MSVCP90D.dll)
  3>libcpmtd.lib(locale0.obj) : error LNK2005: "public: static void __cdecl std::_Locinfo::_Locinfo_ctor(class std::_Locinfo *,class std::basic_string,class std::allocator > const &)" (?_Locinfo_ctor@_Locinfo@std@@SAXPAV12@ABV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@2@@Z) already defined in msvcprtd.lib(MSVCP90D.dll)
  3>libcpmtd.lib(locale0.obj) : error LNK2005: "public: static void __cdecl std::_Locinfo::_Locinfo_dtor(class std::_Locinfo *)" (?_Locinfo_dtor@_Locinfo@std@@SAXPAV12@@Z) already defined in msvcprtd.lib(MSVCP90D.dll)
  3>libcpmtd.lib(xlock.obj) : error LNK2005: "public: __thiscall std::_Lockit::_Lockit(int)" (??0_Lockit@std@@QAE@H@Z) already defined in msvcprtd.lib(MSVCP90D.dll)
  3>libcpmtd.lib(xlock.obj) : error LNK2005: "public: __thiscall std::_Lockit::~_Lockit(void)" (??1_Lockit@std@@QAE@XZ) already defined in msvcprtd.lib(MSVCP90D.dll)
  </code></pre>