Is this code valid C++?

Question

Is the following code valid C++?

const int  var = 10;
{ 
   int  var[var]; // why doesn't this give any error ?
}

Note : The code compiles on my g++ compiler.

Answer 1

As-is? No. If it were in the body of a function? Yes.

The first line declares an integer constant named var with a value of 10.

The braces begins a new block. Within that block, a new variable is declared, named var, which is an array of int with a size equal to the value of the integer constant previously declared as var (10).

The key is that var refers to the first variable until after the second variable named var is fully declared. Between the semicolon following the second declaration and the closing brace, var refers to the second variable. (If there was an initializer for the second variable, var would begin to refer to the second variable immediately before the initializer.)