Hi List, Robert P. J. Day <rpjday <at> crashcourse.ca> writes: > > > i'm curious about the fact that a small number of header files that > are exported to user space have preprocessor checks for *not* defined > __KERNEL__, as in: > > linux/acct.h:#if !defined(CONFIG_M68K) || !defined(__KERNEL__) > video/edid.h:#if !defined(__KERNEL__) || defined(CONFIG_X86) > > it's obvious that the purpose of the check "#ifdef __KERNEL__" is to > prevent some header file content from being exposed to user space. > but to check for the opposite just strikes me as kind of weird -- it's > saying that there's some content that *shouldn't* be in kernel space, > but should be available in user space, and i don't see why the kernel > should be defining that kind of content. > > any rationale for this sort of thing? thanks. I am not sure whether I am right - but I was wondering what would happen in case of 32 bit libraries working on 64bit Kernel - You don't want kernel to look at a header file containing some 32bit defines. But that is exactly what the user space wants: 32bit defines hidden from a 64bit kernel. if !__KERNEL__ would make sure that user-space gets what kernel should not. I don't have an example of a such a scenario, so possible this is more of a blind-shot. THanks and apologies if that is misleading/wrong. Shreyansh -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
