C / C++ / MFC

2 Errors:
a) Lambda does not not with static var, so I must to work wwith bind
b) I try to invoke functions of class from DLL, saved in unordered_map object and fall.If to invoke functions of class not from DLL it is work properly.
How can this problem be solved?


	file UnorderedMapFunctions.cpp
<pre lang="C++">#include <iostream>
#include <unordered_map>
#include <functional>
#include <windows.h>

#include "..\\Geometry\\Geometry.h"
using namespace std;

namespace NS
{
  class Math
  {
  public:
    int Sum(int x, int y) { return x + y; }
    int Sub(int x, int y) { return x - y; }
    int Mul(int x, int y) { return x * y; }
    int Div(int x, int y) { return x / y; }
  };
}
using namespace NS;

int main()
{
  unordered_map<string, function<int(int, int)>>* mydata = new unordered_map<string, function<int(int, int)>>;
  Math* m = new Math;
 
  // Using lambda functions to bind member functions
  (*mydata)["sum"] = [m](int x, int y) { return m->Sum(x, y); };
  (*mydata)["sub"] = [m](int x, int y) { return m->Sub(x, y); };
  (*mydata)["mul"] = [m](int x, int y) { return m->Mul(x, y); };
  (*mydata)["div"] = [m](int x, int y) { return m->Div(x, y); };
  /*
  //Geometry* g = new Geometry;
  (*mydata)["circle"] = [g](int x, int y) { return g->Circle(x, y); };
  (*mydata)["rectangle"] = [g](int x, int y) { return g->Rectangle(x, y); };
  */
  //==============================================================
  string fullname_dll = "Geometry";
  HINSTANCE hInst = LoadLibraryA(fullname_dll.c_str());
  if (hInst == nullptr)
  {
    cout << "Error: [FuncImport] wrong name " << fullname_dll.c_str() << endl;
    return false;
  }
  typedef void (CALLBACK* CreateInstanceFunc)(unordered_map<string, function<int(int, int)>>* mydata);
  string CreateFuncName = "CreateInstance"; 
  CreateInstanceFunc CreateInstance = (CreateInstanceFunc)GetProcAddress(hInst, CreateFuncName.c_str()); 
  if (CreateInstance == nullptr)
  {
    cout << "Error: wrong name " << fullname_dll << endl;
    FreeLibrary(hInst);
    return false;
  }
  CreateInstance(mydata);
  cout << "Imported " << fullname_dll.c_str();
  FreeLibrary(hInst);
  //==============================================================
  // Invoke by 'key' functions, saved in 'mydata'
  // it is right! 
  for (const auto& [k, v] : *mydata)
    std::cout << "Key: " << k << " Value: " << v(3, 5) << std::endl;
  //===================================
  auto it = mydata->find("circle");
  if (it != mydata->end())
   // Exception thrown: read access violation.
   // fault in functional.h line 920
   // it->second.vfptr = addr(??? ??? ??? ??? ???)
    cout << "\nKey: " << it->first << " Value: " << it->second(4, 2) << std::endl;
  else
    cout << "Error\n";
  //===================================

  delete m;
  delete mydata;
  return 0;
}

#pragma once
#include <iostream>
#include <unordered_map>
#include <functional>
#include <windows.h>

#ifdef GEOMETRY_EXPORTS
#define GEOMETRY_API __declspec(dllexport)
#else
#define GEOMETRY_API __declspec(dllimport)
#endif

using namespace std;
namespace NS
{
  class GEOMETRY_API Geometry
  {
  public:
    Geometry();
    int Circle(int x, int y);
    int Rectangle(int x, int y);
  };
  extern "C" void  GEOMETRY_API  CreateInstance(unordered_map<string, function<int(int, int)>>* mydata);
  extern "C" void  GEOMETRY_API  Cleanup();
}

#include "pch.h"
#include "Geometry.h"

namespace NS
{
   Geometry* geometryInstance;
  void CreateInstance(unordered_map<string, function<int(int, int)>>* mydata)
  {
    geometryInstance = new Geometry;
    // Can't capture a static variable in a lambda
    //(*mydata)["circle"] = [geometryInstance](int x, int y) { return geometryInstance->Circle(x, y); };
    //(*mydata)["rectangle"] = [geometryInstance](int x, int y) { return geometryInstance->Rectangle(x, y); };

    (*mydata)["circle"] = bind(&Geometry::Circle, geometryInstance, placeholders::_1, placeholders::_2);
    (*mydata)["rectangle"] = bind(&Geometry::Rectangle, geometryInstance, placeholders::_1, placeholders::_2);
  }
  Geometry::Geometry() {}
  int Geometry::Circle(int x, int y) { return 3.14 * x * x; }
  int Geometry::Rectangle(int x, int y) { return x * y; }
  void Cleanup()
  {
        delete geometryInstance;
        geometryInstance = nullptr;
  }
}