#include <stdio.h>
#include <stdint.h>

typedef struct {
    char const *s1;
    char const *s2;
} S;

typedef void (*callback_fn)(S s, char const *data);

#ifdef _MSC_VER
#define EXPORT __declspec(dllexport)
#else
#define EXPORT __attribute__((visibility("default")))
#endif

EXPORT extern void ccb(callback_fn fn) {
    char const *data = "Let's be together, forever, we are never gonna be apart.";

    fprintf(stderr, "(C) address of data = %p\n", (void*)data);

    fn(
        ((S) {
            "Shall I leave you be, Is it love if I can set you free?",
            "But even it's not reality,",
        }),
        data
    );
}