On 10/22/2009 04:02 PM, Trond Myklebust wrote: > On Thu, 2009-10-22 at 10:18 +0200, Boaz Harrosh wrote: >> On 10/22/2009 02:28 AM, Trond Myklebust wrote: >>> On Wed, 2009-10-21 at 10:14 +0200, Boaz Harrosh wrote: >>>> An header should be compilation independent, .i.e pull in >>>> any header who's declarations are directly used by this header. >>>> And not let users re-include all it's dependencies all over >>>> again. >>>> >>>> [At the end of the day what's the use of a header if it does >>>> not have more then one user?] >>> >>> >>> The problem with this is that you quickly end up including the same >>> header files over and over and over again as they get pulled in several >>> times over by different headers. >>> >>> >>> >> >> What is the problem with that? >> >> two things: >> 1. it is unavoidable. >> 2. That's why we invented the #ifndef FOO_H #define FOO_H for. >> 3. Look at the current mess, to the point that you don't understand why >> the code does not compile, you end up just copy-past the include list >> of that other file, and now actually do end with extra un-needed includes. >> (Don't believe me look at the last patch as proof). >> 4. So I add to an header a use of a type that now needs a new include. >> All my users do not compile any more. What to do? OK I'll include it so >> not to change all existing users all over again. Now we get a double >> standard. All headers used before any users, must be carried around. >> The late comers are escaped. >> 5. The opposite of 4. An header is no longer needed. Extra header left at all >> users. >> >> It used to be a problem before me and you have begun programing. >> Since then the cpp looks at it's internal structures and will not re-open. >> Note that the compiler never sees the second instance, ever. >> >> That said we have no choice of the matter. It is a Kernel style guide. I >> should know because I was banged on the head with it a couple of times. >> And rightly so. >> >> Come on that was a joke right >> Boaz > > No. What I'm saying is that this doesn't have to be an absolute rule. > The Kernel style guide assumes that everything in 'include/*' is going > to be exported all around the kernel. > The problem is that we put a lot of stuff which is private to fs/nfs and > fs/nfsd in there. Those header files do not have to absolutely follow > the style guide rule, 'cos we know what is being included before and > after them... > I'm not sure I understand You are saying that the patches are very good, but only the rule I stated originally could be relaxed a little with private headers where we might get lazy, if the effects are very local? Well, that's not a problem then, right? just that I can relax a bit if I want. But I disagree: see 3, 4, 5 above and that last patch I submitted. That patch is only the beginning. 85% of all source files in nfs/nfsd could receive the same love. I only done these I touched. Code tends to stay much-much longer then we spend time on it. Better get it in shape the first time. > Cheers > Trond > I've now compiled this with x86 allmodeconfig. It should stay in linux-next for a while to make sure there's no side effects. Boaz -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
