From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Date: Fri, 06 Feb 2009 16:33:14 +0000 Subject: Re: [linux-next][PATCH] revert headers_check fix: ia64, fpu.h Message-Id: <20090206163314.GA11216@elte.hu> List-Id: References: <20090206164546.6291.KOSAKI.MOTOHIRO@jp.fujitsu.com> <3f9a31f40902060053x18dacf58u40c739ab89f13860@mail.gmail.com> <20090206180957.6294.KOSAKI.MOTOHIRO@jp.fujitsu.com> <20090206145556.GH18368@elte.hu> <1233934141.3209.20.camel@localhost.localdomain> <20090206153315.GD13758@n2100.arm.linux.org.uk> <1233935328.3209.30.camel@localhost.localdomain> <20090206155512.GF13758@n2100.arm.linux.org.uk> <20090206161229.GA8256@elte.hu> <20090206162352.GI13758@n2100.arm.linux.org.uk> In-Reply-To: <20090206162352.GI13758@n2100.arm.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Russell King - ARM Linux Cc: Jaswinder Singh Rajput , KOSAKI Motohiro , Jaswinder Singh Rajput , Linus Torvalds , Sam Ravnborg , Andrew Morton , hskinnemoen@atmel.com, cooloney@kernel.org, tony.luck@intel.com, ralf@linux-mips.org, dhowells@redhat.com, matthew@wil.cx, chris@zankel.net, LKML , linux-next , linux-ia64 * Russell King - ARM Linux wrote: > On Fri, Feb 06, 2009 at 05:12:29PM +0100, Ingo Molnar wrote: > > > > * Russell King - ARM Linux wrote: > > > > > > We cannot see any downside of this patch. > > > > > > > > But we can see upside of this patch is: > > > > 1. No need to protect linux/types.h with #ifndef __ASSEMBLY__ in many > > > > files > > > > 2. So we trying to replace multiple #ifndef __ASSEMBLY__ with one. > > > > > > The point is: > > > > > > 1. If the parent include needs to include linux/types.h to get at C > > > types _and_ the include file needs to also be included by assembly > > > code, it itself needs to have #ifndef __ASSEMBLY__ to protect those > > > uses from the assembly code. > > > > > > In that case, the linux/types.h include should be contained within > > > the #ifndef __ASSEMBLY__ .. #endif block along with all C only > > > parts of the header file. > > > > That makes the code much less clean: putting #include's in the middle of a > > header is poor style and leads to people failing to consider dependencies. > > We generally put them to the header portion. > > > > Putting an #include line in the middle of a header file is a receipe for a > > dependency hell (it can easily fall inside #ifdefs, can be overlooked, > > etc.), so it's _strongly_ discouraged (at least on arch/x86). > > Put them at the top then with an additional ifndef. So you advocate 40 stupid pairs of #ifdefs spread out, instead of a _single_, obvious #ifdef in a commonly used header? Case closed. Ingo