From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Subject: Re: [PATCH v2] qemu: replace "" with <> in headers Date: Wed, 21 Mar 2018 15:54:24 +0000 Message-ID: <20180321155424.GV8551@redhat.com> References: <1521642402-197739-1-git-send-email-mst@redhat.com> <20180321151922.GR8551@redhat.com> <20180321173309-mutt-send-email-mst@kernel.org> Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Cc: Peter Maydell , Dmitry Fleytman , Pavel Dovgalyuk , Li Zhijian , David Hildenbrand , Stefan Hajnoczi , qemu-devel@nongnu.org, BALATON Zoltan , Keith Busch , Max Filippov , Hannes Reinecke , Gerd Hoffmann , Fam Zheng , Max Reitz , Stefano Stabellini , zhanghailiang , Ben Warren , Stefan Berger , Yongbok Kim , Michael Roth , "Richard W.M. Jones" , Christian Borntraeger , =?utf-8?B?SGVydsOp?= Poussinea To: "Michael S. Tsirkin" Return-path: Content-Disposition: inline In-Reply-To: <20180321173309-mutt-send-email-mst@kernel.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-block-bounces+gceqb-qemu-block=m.gmane.org@nongnu.org Sender: "Qemu-block" List-Id: kvm.vger.kernel.org On Wed, Mar 21, 2018 at 05:39:48PM +0200, Michael S. Tsirkin wrote: > On Wed, Mar 21, 2018 at 03:19:22PM +0000, Daniel P. Berrang=C3=A9 wrote= : > > On Wed, Mar 21, 2018 at 04:46:32PM +0200, Michael S. Tsirkin wrote: > > > Our current scheme is to use > > > #include "" > > > for internal headers, and > > > #include <> > > > for external ones. > > >=20 > > > Unfortunately this is not based on compiler support: from C point o= f > > > view, the "" form merely looks up headers in the current directory > > > and then falls back on <> directories. > > >=20 > > > Thus, for example, a system header trace.h - should it be present -= will > > > conflict with our local trace.h > >=20 > > If our local "trace.h" is in the current directory, then using "" > > is right and you can still use to get the system version. > >=20 > > If our local trace.h is in include/ top level, then it is going to > > block use of the system trace.h regardless of whether we use <> or "" > >=20 > > Fortunately our include/ tree uses sub-dirs, so we would typically > > use #include "$subdir/trace.h" and #include would still > > find the system header. > > We just have to be careful we don't add stuff at the top level of > > our include/ dir with names that are liable to clash. This might > > suggest renaming include/elf.h to include/qemu/elf.h, or just > > moving elf.h to the qemu/ subdirectory. Likewise include/glib-compat.= h > > might be better moved to qemu/ subdirectory. > >=20 >=20 > This is exactly what this patch proposes, with a uniform scheme: > start everything with qemu/. >=20 > >=20 > > > As another example of problems, a header by the same name in the so= urce > > > directory will always be picked up first - before any headers in > > > the include directory. > >=20 > > There's only a couple of headers in the top level of our include/ > > directory - everything else is pulled in with a named path > > eg #include "block/block_int.h", so that would not conflict with > > reference to a bare #include "block_int.h" from the current directory= . >=20 > We can not know that there are no system headers that start with block/= on > any current or future systems. Ah true, good point. I guess that's where the benefit of -iquote comes into play. Regards, Daniel --=20 |: https://berrange.com -o- https://www.flickr.com/photos/dberran= ge :| |: https://libvirt.org -o- https://fstop138.berrange.c= om :| |: https://entangle-photo.org -o- https://www.instagram.com/dberran= ge :|