main.c

#include <stdio.h>

#ifdef _WIN32
#include <windows.h>
#else
#include <dlfcn.h>
#endif

#ifdef _WIN32
#define EXPORT __declspec(dllexport)
#else
#define EXPORT
#endif

EXPORT int multiplier(int a, int b)
{
    return a * b;
}

EXPORT void *aiv_open_lib(const char *name)
{
#ifdef _WIN32
    // get address of the current process symbols table
    if (name == NULL)
        return GetModuleHandle(NULL);
    return LoadLibrary(name);
#else
    return dlopen(name, RTLD_LAZY);
#endif
}

EXPORT void *aiv_lib_symbol(void *lib, const char *name)
{
#ifdef _WIN32
    return GetProcAddress(lib, name);
#else
    return dlsym(lib, name);
#endif
}

static int call_add(int a, int b)
{
    
    void *plugin = aiv_open_lib("libfoo.dll");
    if (!plugin) 
    {
        fprintf(stderr, "adder() is not implemented\n");
        return -1;
    }
    int (*adder)(int, int) = aiv_lib_symbol(plugin, "adder");
    if (!adder)
    {
        fprintf(stderr, "adder() is not implemented\n");
        return -1;
    }
    // adder is now a valid function pointer
    fprintf(stdout, "plugin loaded at %p: %d\n", plugin, adder(a, b));
    return -1;
}

int main(int argc, char *argv[])
{
    fprintf(stdout, "hello i am main()\n");
    call_add(17, 22);

    void *myself = aiv_open_lib(NULL);
    fprintf(stdout, "myself available at %p\n", myself);

    fprintf(stdout, "multiplier is at address %p\n", aiv_lib_symbol(myself, "multiplier"));
    fprintf(stdout, "aiv_open_lib is at address %p\n", aiv_lib_symbol(myself, "aiv_open_lib"));
    fprintf(stdout, "aiv_lib_symbol is at address %p\n", aiv_lib_symbol(myself, "aiv_lib_symbol"));

    return 0;
}