加载的库函数如何在主应用程序中调用符号？

#include<windows.h>

typedef int (*FuncPtr)(int, int);

int main() {
    HINSTANCE hDLL = LoadLibrary("mylibrary.dll");
    if (hDLL != NULL) {
        FuncPtr myFunc = (FuncPtr)GetProcAddress(hDLL, "myFunction");
        if (myFunc != NULL) {
            int result = myFunc(1, 2);
            FreeLibrary(hDLL);
            return result;
        }
    }
    return -1;
}

#include <dlfcn.h>

typedef int (*FuncPtr)(int, int);

int main() {
    void *hDLL = dlopen("libmylibrary.so", RTLD_LAZY);
    if (hDLL != NULL) {
        FuncPtr myFunc = (FuncPtr)dlsym(hDLL, "myFunction");
        if (myFunc != NULL) {
            int result = myFunc(1, 2);
            dlclose(hDLL);
            return result;
        }
    }
    return -1;
}

#include<memory>

class MyBase {
public:
    virtual int myFunction(int a, int b) = 0;
};

class MyDerived : public MyBase {
public:
    virtual int myFunction(int a, int b) {
        return a + b;
    }
};

int main() {
    std::shared_ptr<MyBase> pBase = std::make_shared<MyDerived>();
    std::shared_ptr<MyDerived> pDerived = std::dynamic_pointer_cast<MyDerived>(pBase);
    if (pDerived != nullptr) {
        int result = pDerived->myFunction(1, 2);
        return result;
    }
    return -1;
}