   How to use the C++ in C
  here is the question, How to use the C++ in C on VC6.0My strategy is like thisfirst,make a *.dll in cpp,and copy the *.dll and *.lib to the route of the  second filesecond, make the interface file which employs the generated functions in *.dll.   it is an interface bridges the gap between *.c and *.cpp,the   interface also is a *.dll    third, in a *.c file, use the interface dll in the second approachbut in the second setp the system told me "int __cdecl add(int,int)" (?add@@YAHHH@Z)"int __cdecl sun(int,int)" (?sun@@YAHHH@Z)Debug/22c.dll : fatal error LNK1120: 2 unresolved externalsError executing link.exe.22c.dll - 3 error(s), 0 warning(s)and how can i use the interface dll in *.C//-----------------------------------//   FIRST// the cppdll.h#ifndef dynamic#definedynamic_declspec(dllexport) int add(int a, int b);_declspec(dllexport) int sun(int a, int b);#endif// the cppdll.cpp#include "cppdll.h"_declspec(dllexport) int add(int a, int b){return a+b;}_declspec(dllexport) int sub(int a, int b){return a-b;}//-----------------------------------//   SECOND#include   <iostream>   #include   "../22/cppdll.h"   extern   "C"    {   int cpp_add(int a, int b);   int cpp_add(int a, int b){return add(a,b);}int cpp_sun(int a, int b);   int cpp_sun(int a, int b){return sun(a,b);}    }  //-----------------------------------//-----------------------------------//Third// ????????????????????????main(){   int x, y, z;   x=1; y=2;   z = add(x,y);}//-----------------------------------   
  Declare your interface functions as extern "C".   