do {} while(0) is a common idiom for macros in C, because it consumes the trailing semicolon, which a bare {} block doesn't do. if(x) MACRO(); else som

do {} while(0) is a common idiom for macros in C, because it consumes the trailing semicolon, which a bare {} block doesn't do. if(x) MACRO(); else something(); expands to if(x) { ... }; // Error! else something();