16.1.1 Boolean Constant Expressions

V is definitely assigned after any constant expression whose value is true when false. V is definitely assigned after any constant expression whose value is false when true.

A constant expression whose value is true never has the value false, and a constant expression whose value is false never has the value true, these definitions are vacuously satisfied. They are helpful in analyzing expressions involving the boolean operators &&, ||, and ! (§16.1.3, §16.1.4, §16.1.5).