test.cpp

#include <stddef.h>

struct SaveLoad {
    bool global;
    void *address;
};

static inline void *GetVariableAddress(const void *object, const SaveLoad *sld)
{
        return const_cast<unsigned char *>((const unsigned char*)(sld->global ? nullptr : object) + (ptrdiff_t)sld->address);
}


struct Settings {
    int a;
    int b;
    int c;
    int d;
};

Settings settings;

void setup1() __attribute__ ((optnone));
struct SaveLoad *setup2() __attribute__ ((optnone));

void setup1() {
    settings.a = 11;
    settings.b = 22;
    settings.c = 33;
    settings.d = 44;
}

struct SaveLoad *setup2() {
    SaveLoad *sl = new SaveLoad();
    sl->global = true;
    sl->address = &settings.c;
    return sl;
}

int test1() {
    setup1();
    SaveLoad *sl = setup2();

    void *ptr1 = GetVariableAddress(nullptr, sl);
    return *((int*)ptr1);
}

int test2() {
    setup1();
    SaveLoad *sl = setup2();

    void *ptr1 = GetVariableAddress(&settings, sl);
    return *((int*)ptr1);
}

#include <stdio.h>
int main()
{
	printf("%d, %d\n", test1(), test2());
	return 0;
}