On Tue, 2007-02-20 at 19:40 +0000, Daniel P. Berrange wrote: Dunno, I much prefer the active flag purely for readability. e.g. while (vm) { if (vm->id != -1) shutdown(vm); vm = vm->next; } would make me carefully check whether ->id means active the first time I see it and while (vm) { if (vm->pid != -1) shutdown(vm); vm = vm->next; } would make me check *every* time I see it, whereas I'd never feel the need to verify this: while (vm) { if (vm->active) shutdown(vm); vm = vm->next; } i.e. several times already when tracking down bugs I've felt suspicious about whether ((id != -1) != active) in places ... Perhaps we just need a macro or static inline: static inline qemudIsActiveVM(struct qemud_vm *vm) { return vm->id != -1; } Cheers, Mark.