Simple use of a canary

canary.c

#include <stdio.h>
#include "lib.h"

#define CANARY_VALUE 0x42424242

int main(void)
{
    int lib_data[LIB_DATA_SIZE+1];          /* Allocating lib data plus one element (the canary) */
    int *canary = &lib_data[LIB_DATA_SIZE]; /* the canary is just after the lib_data */
    *canary = CANARY_VALUE;                 /* Setting the canary */

    calling_the_lib(lib_data);              /* Calling the somewhat "shady" lib */

    if(*canary != CANARY_VALUE)            /* Testing the canary */
        printf("Poor Canary died and lib did a buffer overflow\n");

    return 0;

}