c++ - Linker can't find function definitions, LNK2001 unresolved external symbol -

here simple setup: (i've hidden lots of unneeded information)

//autofocustest.h #include "camavtex.h"  class cautofocustestapp : public cwinapp { protected:     camera_t* mcamera;  public:     virtual bool initinstance(); };  //camavtex.h class camera_avtcam_ex_t : public camera_t { public:     camera_avtcam_ex_t();     virtual ~camera_avtcam_ex_t();      //member variables      //member function declarations }  //camavtex.cpp #include "camavtex.h"  camera_avtcam_ex_t::camera_avtcam_ex_t() {     //stuff }  camera_avtcam_ex_t::~camera_avtcam_ex_t() {     //stuff }  //the rest defined here in program  //autofocustest.cpp #include autofocustest.h  bool cautofocustestapp::initinstance() {     mcamera = new camera_avtcam_ex_t(); } 

this setup produces error:

3>autofocustest.obj : error lnk2001: unresolved external symbol "public: __cdecl camera_avtcam_ex_t::camera_avtcam_ex_t(void)" (??0camera_avtcam_ex_t@@qeaa@xz)

from i've read on relatively common problem, have not linked causing camera_avtcam_ex_t function definitions not found. however, can't figure out have missed. have added of include directories , library directories, added library files additional dependencies section.

can spot might missing?

assuming have defined constructor camera_avtcam_ex_t, it's declared private, can't instantiate it.