Foward declaration, that is. You can vaguely compare it to function prototypes. On 1 June 2012 15:00, Bernd Petrovitsch <bernd@xxxxxxxxxxxxxxxxxxx> wrote: > Hi! > > On Don, 2012-05-31 at 01:37 +0800, harryxiyou wrote: >> On Thu, May 31, 2012 at 1:20 AM, Gaurav Jain <gjainroorkee@xxxxxxxxx> wrote: > [...] >> > Those are forward declarations as they are being used in defining struct >> > bus_attribute. It's nothing special about GNU-C. That's the case for ANSI-C >> > too. Pretty standard. > > These actually exists since K&R times. > >> Hmmm.., that is to say, they may be used before definitions in this file or >> defined in other files like 'struct iommu_ops;' field (Actually, i can > > Yes, that's the only reason. And you can't use it if you need the actual > size of that struct because the compiler doesn't know it (yet). > The main usage scenario is if you need a pointer to it. > >> not find this field's >> definition in this file). However, if it has been defined in other >> header files, we need >> not declare here, right? > > If you #include that other file, yes. > But it is not trivial in very large projects like the Linux kernel to > keep somewhat logical and clean and circular-free -h files. > And you also do not really want a separate .h file for each struct. > > Bernd > -- > Bernd Petrovitsch Email : bernd@xxxxxxxxxxxxxxxxxxx > LUGA : http://www.luga.at > > > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies@xxxxxxxxxxxxxxxxx > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
