Why I do not get errors when I initilize array container with more elemts than the size of the array?

I noticed that when I initialize array like so:

std::array<int,3> myarray;

myarray[0] = 9;
myarray[1] = 8;
myarray[2] = 7;
myarray[3] = 6;
myarray[4] = 5;

I do not get an error, even though I have more array elements than was defined in <int,3>

I am on Mac with g++ and it's C++11.

So i guess my question is: why is that, that there are no errors? Is it correct behavior? Or do I expect too much form my compiler?

Also what is this method of initialization called? Someone called it "buggy construction". I think they meant it as a joke though.

P.S. I understand that this method is undesirable.