Compilers that do not whine about the first two examples do not strictly conform to the standards, since the "return" statement requires a terminating semicolon. The only C statement that does not require a terminating semicolon is the compound statement (or block), which is delimited by braces ({ }).

As for the second two examples, another rule for C statements is that "control" expressions appearing in conditional and iterative statements be enclosed in parentheses. Since "return" is neither a conditional nor iterative statement, its syntax is "return expression ;". For expression usage in this context, the purpose of the optional parentheses is simply to delimit the enclosed expression for grouping purposes, either to defeat the default precedence of operators or make the code more readable.