Expression statements have the form
expression-statement: expressionopt ;
The expression is a discarded-value expression (Clause [expr]). All side effects from an expression statement are completed before the next statement is executed. An expression statement with the expression missing is called a null statement. [ Note: Most statements are expression statements — usually assignments or function calls. A null statement is useful to carry a label just before the } of a compound statement and to supply a null body to an iteration statement such as a while statement ([stmt.while]). — end note ]