Useful C Macros

Let's share the macros we use that make our C code really EXPERT!!

Right now I'm specifically interested in macros to add half-assed object orientation. Thanks!!

I'll contribute myself:
#define mainstart int main(int argc, char **argv) {

#if DEBUG
#define log(...) fprintf(stderr, __VA_ARGS__)
#else
#define log(...) /* nothing */
#endif