gcc -fstack-protector does not throw error

Question

Does someone know why the following lines of code throws a *** stack smashing detected *** error

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

int main(int argc, char **argv)
{
  char x[16];
  strcpy(x,"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa");
}

but the following code does not throw it?

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

int main(int argc, char **argv)
{
    char x[16];
    x[17] = 'a';
}

Thank you!!

Answer 1

Overwriting x[17] doesn't overwite the canary-value put before the return address by gcc.