what is an example of out of bounds read in order to leak sensitive information?

I Am trying to understand a little bit better behind the scenes on bypassing aslr by reading the bytes in the memory of a process, but how can I make an example of an info leak in WIN32? my code does the leaks of bytes , but how can I check the image base based on those bytes?

#include <stdio.h>
#include <string.h>

int main(int argc, char **argv) {
    char a[16];

    strncpy(a, "0123456789abcdef", sizeof(a));

    //... lots of code passes, functions are called...
    //... we finally come back to array a ...

    printf("%sn", a);
}