static array internal & dangling reference

[Picaud Vincent via Digitalmars-d-learn]

Hi all,
Still learning... This time what surprised me is how static 
arrays work.
I assume (is it true?) that for efficiency reason static size 
arrays like int[10] are on the stack and do not involve dynamic 
memory allocation:

First surprise: it is possible to share a static array:

void main() {

   int[10] sa;
   foreach(int i, ref sa_i;sa){
     sa_i=i;
   }
   writeln("\n vect init sa",sa);

   int[] sb=sa[3..6];       // <- did not think it was possible
   sb[2]=100;

   writeln("\n vect sa ",sa);
   writeln("\n vect sb ",sb);
}

which prints:

  vect init sa[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

  vect sa [0, 1, 2, 3, 4, 100, 6, 7, 8, 9]  // <- sa and sb are 
really shared

  vect sb [3, 4, 100]

Second surprise: I tried to create a dangling reference with:

int[] f()
{
   int[10] sa;
   foreach(int i, ref sa_i;sa){
     sa_i=i;
   }
   int[] sb=sa;
   return sb;
}

void f_test()
{
   auto sb=f();
   sb[2]=100; // I expected an "invalid access" (it points to 
"sa", a local variable)
}

However calling f_test seems ok and valgrind tool does not 
complain...

So my questions are:
0/ does I miss something? (in C++ for sure you create a dangling 
pointer)
1/ what is the internal mechanism for that? Is the GC involved? 
Performance impact?
2/ any link describing this in more details is welcome

Thank you