A.7.3.1 Array References
A postfix expression followed by an expression in square brackets is a postfix expression denoting a subscripted array reference. One of the two expressions must have type pointer to T, where T is some type, and the other must have integral type; the type of the subscript expression is T. The expression E1[E2] is identical (by definition) to *((E1)+(E2)). See Par.A.8.6.2 for further discussion.