The following example demonstrates memory access outside the boundary of an array:

#include <iostream>
using namespace std;

int main ( ) {
    int a[10];

    a[10] = 100;
    cout << a[10] << endl;

    return 0;
}

The following output shows the valgrind debug session that precisely points to memory access outside the boundary of the array:

g++ arrayboundsoverrun.cpp -g -std=c++17 

jegan@ubuntu  ~/MasteringC++/Debugging  valgrind --track-origins=yes --read-var-info=yes ./a.out
==28576== Memcheck, a memory error detector
==28576== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==28576== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info
==28576== Command: ./a.out
==28576== 
100
*** stack smashing detected ***: ./a.out terminated
==28576== 
==28576== Process terminating with default action of signal 6 (SIGABRT)
==28576== at 0x51F1428: raise (raise.c:54)
==28576== by 0x51F3029: abort (abort.c:89)
==28576== by 0x52337E9: __libc_message (libc_fatal.c:175)
==28576== by 0x52D511B: __fortify_fail (fortify_fail.c:37)
==28576== by 0x52D50BF: __stack_chk_fail (stack_chk_fail.c:28)
==28576== by 0x4008D8: main (arrayboundsoverrun.cpp:11)
==28576== 
==28576== HEAP SUMMARY:
==28576== in use at exit: 72,704 bytes in 1 blocks
==28576== total heap usage: 2 allocs, 1 frees, 73,728 bytes allocated
==28576== 
==28576== LEAK SUMMARY:
==28576== definitely lost: 0 bytes in 0 blocks
==28576== indirectly lost: 0 bytes in 0 blocks
==28576== possibly lost: 0 bytes in 0 blocks
==28576== still reachable: 72,704 bytes in 1 blocks
==28576== suppressed: 0 bytes in 0 blocks
==28576== Rerun with --leak-check=full to see details of leaked memory
==28576== 
==28576== For counts of detected and suppressed errors, rerun with: -v
==28576== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
[1] 28576 abort (core dumped) valgrind --track-origins=yes --read-var-info=yes ./a.out

As you will notice, the application crashed with core dump due to illegal memory access.  In the preceding output, the Valgrind tool accurately points to the line that caused the crash.