Multiple LNK2005 errors

Question

I'm compiling a project and have the following errors:

  LIBCMTD.lib(_file.obj) : error LNK2005: ___iob_func already defined in      MSVCRTD.lib(MSVCR90D.dll)
  LIBCMTD.lib(dbgheap.obj) : error LNK2005: __CrtSetCheckCount already defined in MSVCRTD.lib(MSVCR90D.dll)
  LIBCMTD.lib(crt0dat.obj) : error LNK2005: _exit already defined in MSVCRTD.lib(MSVCR90D.dll)
  LIBCMTD.lib(crt0dat.obj) : error LNK2005: __exit already defined in MSVCRTD.lib(MSVCR90D.dll)
  LIBCMTD.lib(crt0dat.obj) : error LNK2005: __cexit already defined in MSVCRTD.lib(MSVCR90D.dll)
  LIBCMTD.lib(crt0dat.obj) : error LNK2005: __amsg_exit already defined in MSVCRTD.lib(MSVCR90D.dll) 
  LIBCMTD.lib(crt0dat.obj) : error LNK2005: __initterm_e already defined in MSVCRTD.lib(MSVCR90D.dll)
  LIBCMTD.lib(fflush.obj) : error LNK2005: _fflush already defined in MSVCRTD.lib(MSVCR90D.dll)
  LIBCMTD.lib(dbghook.obj) : error LNK2005: __crt_debugger_hook already defined in MSVCRTD.lib(MSVCR90D.dll)
  LIBCMTD.lib(invarg.obj) : error LNK2005: __invoke_watson already defined in MSVCRTD.lib(MSVCR90D.dll)
  LIBCMTD.lib(setlocal.obj) : error LNK2005: __configthreadlocale already defined in MSVCRTD.lib(MSVCR90D.dll)
  LIBCMTD.lib(tidtable.obj) : error LNK2005: __encode_pointer already defined in MSVCRTD.lib(MSVCR90D.dll)
  LIBCMTD.lib(tidtable.obj) : error LNK2005: __decode_pointer already defined in MSVCRTD.lib(MSVCR90D.dll)
  LIBCMTD.lib(sprintf.obj) : error LNK2005: _sprintf already defined in MSVCRTD.lib(MSVCR90D.dll)
  LIBCMTD.lib(crt0init.obj) : error LNK2005: ___xi_a already defined in MSVCRTD.lib(cinitexe.obj)
  LIBCMTD.lib(crt0init.obj) : error LNK2005: ___xi_z already defined in MSVCRTD.lib(cinitexe.obj)
  LIBCMTD.lib(crt0init.obj) : error LNK2005: ___xc_a already defined in MSVCRTD.lib(cinitexe.obj)
  LIBCMTD.lib(crt0init.obj) : error LNK2005: ___xc_z already defined in MSVCRTD.lib(cinitexe.obj)

When I remove two libraries, those errors stop appearing, but I have some unresolved internal symbols errors. So I have to maintain those libraries. Is there a way that I can ignore already defined functions so I don't have the LNK2005 error?

Answer 1

You are linking your project with two versions of run-time library: LIBCMTD.lib (static multithreaded debug) and MSVCRTD.lib (multithreaded debug DLL). How come both of these two versions are present in your project at the same time is impossible to say without knowing more about your setup.

Things like that might happen if you add third-party libraries to your project that demand different versions of run-time library.

This can often be worked around by using

Project Properties -> Linker -> Input -> Ignore Specific Default Libraries

setting in Project Properties for your executable. Decide which library you want to work with (LIBCMTD.lib or MSVCRTD.lib) and ask the linker to ignore the other one.