Kernel开发 - SubmittingPatches，有关ifdef和static inline & macro

From: Documentation/SubmittingPatches

2) #ifdefs are ugly

Code cluttered with ifdefs is difficult to read and maintain. Don't doit. Instead, put your ifdefs in a header, and conditionally define'static inline' functions, or macros, which are used in the code.Let the compiler optimize away the "no-op" case.Simple example, of poor code: dev = alloc_etherdev (sizeof(struct funky_private)); if (!dev) return -ENODEV; #ifdef CONFIG_NET_FUNKINESS init_funky_net(dev); #endifCleaned-up example:(in header) #ifndef CONFIG_NET_FUNKINESS static inline void init_funky_net (struct net_device *d) {} #endif(in the code itself) dev = alloc_etherdev (sizeof(struct funky_private)); if (!dev) return -ENODEV; init_funky_net(dev);3) 'static inline' is better than a macroStatic inline functions are greatly preferred over macros.They provide type safety, have no length limitations, no formattinglimitations, and under gcc they are as cheap as macros.Macros should only be used for cases where a static inline is clearlysuboptimal [there are a few, isolated cases of this in fast paths],or where it is impossible to use a static inline function [such asstring-izing].'static inline' is preferred over 'static __inline__', 'extern inline',and 'extern __inline__'.