new int[2] () is broken in 3.4.x, see PR 20427.

Testcase which was attached on PR 20427:


#include <iostream>
void f(int n)
{
    int * a = new int [n] () ;
    for (int i = 0; i < n; ++i)
    {
        std::cout << a[i]++ << ' ';
    }
    std::cout << '\n';
    delete[] a;
}

int main()
{
    f(5);
    f(5);
    f(5);
    f(5);
}

Which shows the issue more clearer.

3.2.3 and 3.0.4 rejected the code:
t.cc: In function `void f(int)':
t.cc:4: variable-sized object of type `int[n]' may not be initialized

No recent (from 2.95.3 and above) GCC version got this right (well at least the versions I tested).

Here is a self contained testcase which fails and should not:
extern "C" void abort ();
void f(int n)
{
    int * a = new int [n] () ;
    for (int i = 0; i < n; ++i)
    {
        if (a[i])
                abort ();
        a[i]++;
    }
    delete[] a;
}
int main()
{
    f(5);
    f(5);
    f(5);
    f(5);
}

Even ICC 8.1 gets this wrong :).

Fixed for 4.0.3 and above.