OK, now i understand better what your question is about. For reference i modified your program this way:

Code:

#include <iostream>
using namespace std;

int main()
{
        const int index=1000;
        int numbers[8] = {1,2,3,4,5,6,7,8};

        numbers[index] = 999;
        cout << numbers[index] << endl;

        return 0;
}

and used this compiler version:

Code:

# g++ --version
g++ (Ubuntu 5.4.0-6ubuntu1~16.04.6) 5.4.0 20160609
Copyright (C) 2015 Free Software Foundation, Inc.

with the same results.

The problem IMHO is a misunderstanding of runtime-bounds-checking and compile-time bounds-checking. Runtime bounds-checking is included in the frontend (if at all) and this is only done for C but not for C++ according to this source. The link also mentions other options (mudflap, MIRO, valgrind, ...), which i haven't tested at all (i haven't programmed anything worthwhile in a HLL for a long time).

As far as i have understood the GNU compiler suite allows for switching on runtime bounds-checking, which the C-frontend does provide but the g++-frontend does not.

None of the frontends do compile-time bounds-checking (which you seem to be after) and, frankly, i doubt this is possible to do in a general way. The compiler would have to guess at compile-time which values any expression could evaluate to, which not only would need arbitrary computing time but also would need to decide the "Entscheidungsproblem - Wikipedia", which is proven to be undecidable (see also "halting problem in Turing-machines").

I hope this helps.

bakunin