Dynamic loading of a lib

Loader.cpp

#define MAJOR_VER 1
#define MINOR_VER 0

#ifdef _WIN32
#define WINDOWS
#endif

#ifdef WINDOWS
#include <Windows.h>
#include <delayimp.h>
#include "Psapi.h"
#pragma comment(lib, "Psapi")
#pragma comment(lib, "Kernel32")
#else
#include <dlfcn.h>
#endif

#include <iostream>
#include <stdio.h>

#ifdef WINDOWS
#define LIBAPI __stdcall
#else
#define LIBAPI
#endif

inline void * loadLibrary(const char* name) {
    printf("Loading %s...\n", name);

#ifdef WINDOWS
    return LoadLibrary(name);
#else
    return dlopen(name, RTLD_NOW);
#endif
}

inline void (*getProcAddress(void * lib, const char *name))(void) {
#ifdef WINDOWS
    return (void (*)(void)) GetProcAddress((HMODULE) lib, name);
#else
    return (void (*)(void)) dlsym(lib, (const char *) name);
#endif
}

inline int freeLibrary(void *lib) {
#ifdef WINDOWS
    return FreeLibrary((HMODULE) lib);
#else
    return dlclose(lib);
#endif
}

#ifdef WINDOWS
 std::string dlerror(){
     return "error load DLL";
 }
#endif

typedef int (LIBAPI *get_version_pt)(int *major, int *minor);

class Loader {
public:

    Loader() {
        p_lib = NULL;
        get_version = NULL;
        libLoaded = false;
    }

    ~Loader() {
        if (p_lib)
            freeLibrary(p_lib);
    }

    int loadLib() {
#ifdef WINDOWS
        const char* lib_name = "my_lib.dll";
#else
        const char* lib_name = "libmy_lib.so";
#endif
        // load library
        if ((p_lib = loadLibrary(lib_name)) != NULL) {
            //libLoaded = true;
        } else {
            fprintf(stderr, "loadLibrary: %s\n", dlerror());
            return 1;
        }

        if ((get_version = (get_version_pt) getProcAddress(p_lib, "get_version")) == NULL) {
            fprintf(stderr, "getProcAddress (get_version): %s\n", dlerror());
            return 1;
        } else {
            int major, minor;
            get_version(&major, &minor);
            if (!(major == MAJOR_VER && minor == MINOR_VER)) {
                printf("Incompatible my_lib version (found %d.%d, required %d.%d)\n", major, minor, MAJOR_VER, MINOR_VER);
                return 1;
            }
        }

        libLoaded = true;
        return 0;
    }

    //private:
    void* p_lib = NULL;
    get_version_pt get_version = NULL;
    bool libLoaded = false;
};

int main(){
 
  Loader loader_;
  loader_.loadLib();
  
  int major, minor;
  loader_.get_version(&major, &minor);
  printf("my_lib version %d.%d\n", major, minor);
  
  return 0;
}