#include <stdio.h>

typedef int cb_fun_t(char *);

struct info {
   cb_fun_t* cb_fun;
   int flag;
};

int do_callback(struct info* info) {
    char* str = "Hello World";
    int ret;
    printf("do_callback called with flag=%i\n", info->flag);
    ret = info->cb_fun(str);
    printf("cb_fun returned %i\n", ret);
    return(ret);
}