c++ - Using (or not using) parentheses when initializing an array

Question

In the c++ code that I am reading through there are some arrays initialised like

int *foo = new int[length];

and some like

int *foo = new int[length]();

My quick experimentation could not detect any difference between these two, yet they are used right next to one another.

Is there a difference, if so what?

Edit; since there is an assertion that the first one should give indeterminate output here is a test showing a suspicious number of 0s;

[s1208067@hobgoblin testCode]$ cat arrayTest.cc
//Test how array initilization works
#include <iostream>
using namespace std;
int main(){
int length = 30;
//Without parenthsis
int * bar = new int[length];
for(int i=0; i<length; i++) cout << bar[0] << " ";

cout << endl;
//With parenthsis 
int * foo = new int[length]();
for(int i=0; i<length; i++) cout << foo[0] << " ";


cout << endl;
return 0;
}
[s1208067@hobgoblin testCode]$ g++ arrayTest.cc
[s1208067@hobgoblin testCode]$ ./a.out
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
[s1208067@hobgoblin testCode]$ 

Edit 2; apparently this test was flawed, dont trust it - look at the answers for details

Answer 1

This line default-initializes length ints, which is to say you will get a bunch of ints with indeterminate value:

int *foo = new int[length];

This line value-initializes them instead, so you get all zeros:

int *foo = new int[length]();