Linker errors between multiple projects in Visual C++

Question

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.

Thanks

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:

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)

Answer 1

Without knowing any other detail about your solution it is hard to tell, however Rebuild All, might be helpful. This situation can sometimes occur when there are mixed object files for different architectures.

You might also want to consider using "References" instead of "Dependencies"

EDIT:

After what you have posted it seems that your linkage to standard libraries is inconsistent. Could it be that one of the project links standard libraries statically while others dynamically? (See project properties->linker) Or one to the release runtime, while others to debug? (though the last one should be possible, with caveats)

Answer 2

It is difficult to answer without knowing all the details about your solution, but I will assume your "other" project are set up to produce a .lib file, and the main project then links all these lib files. If that is the case then a possible cause for the errors you are getting is that your projects link to different versions of the runtime library.

From Microsoft's documentation, "All modules passed to a given invocation of the linker must have been compiled with the same run-time library compiler option (/MD, /MT, /LD)."

Try to change all the projects to use the same version of the runtime library. In Visual Studio 2010, this is in the Project's Properties | Configuration Properties | C/C++ | Code Generation | Runtime Library. Choose either Multi-threaded Debug DLL or Multi-threaded Debug (for your debug configuration).

Answer 3

Are the functions in your other projects exported? If they aren't exported, then there is nothing to link to from the main exe, so that would cause the errors. See Exporting from a DLL Using __declspec(export) for more information.

Answer 4

The errors you are getting are 'error LNK2005' where a symbol in the library you are linking (msvcprtd.lib) has already been defined in another library (for example panels.lib). If you add panels.lib to the 'ignore specific library' field (in VS2008 Configuration Properties--> Linker--> Input -->Ignore specific libraries), the errors will stop.