Whats the best way to write a multi-statement cpp macro?
The usual goal is to write a macro that can be invoked as if it were a single function-call statement. This means that the “caller” will be supplying the final semicolon, so the macro body should not. The macro body cannot be a simple brace- delineated compound statement, because syntax errors would result if it were invoked (apparently as a single statement, but with a resultant extra semicolon) as the if branch of an if/else statement with an explicit else clause. The traditional solution is to use #define Func() do { \ /* declarations */ \ stmt1; \ stmt2; \ /* … */ \ } while(0) /* (no trailing ; ) */ When the “caller” appends a semicolon, this expansion becomes a single statement regardless of context. (An optimizing compiler will remove any “dead” tests or branches on the constant condition 0, although lint may complain.) If all of the statements in the intended macro are simple expressions, with no declarations or loops, another technique is to write a single, parenthesized expr
