From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54711) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eyfqm-0007ee-R5 for qemu-devel@nongnu.org; Wed, 21 Mar 2018 11:40:30 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eyfql-0004Et-6S for qemu-devel@nongnu.org; Wed, 21 Mar 2018 11:40:28 -0400 Date: Wed, 21 Mar 2018 17:39:48 +0200 From: "Michael S. Tsirkin" Message-ID: <20180321173309-mutt-send-email-mst@kernel.org> References: <1521642402-197739-1-git-send-email-mst@redhat.com> <20180321151922.GR8551@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20180321151922.GR8551@redhat.com> Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH v2] qemu: replace "" with <> in headers List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= Cc: qemu-devel@nongnu.org, Thomas Huth , Laurent Vivier , Peter Maydell , Dmitry Fleytman , Ronnie Sahlberg , Li Zhijian , David Hildenbrand , Jeff Cody , Zhang Chen , BALATON Zoltan , Keith Busch , Max Filippov , Gerd Hoffmann , Jiri Pirko , Subbaraya Sundeep , Eric Blake , Michael Roth , Marcelo Tosatti , Josh Durgin , Stefano Stabellini , Alberto Garcia , zhanghailiang , Ben Warren , Marcel Apfelbaum , Yongbok Kim , Markus Armbruster , Stefan Berger , Christian Borntraeger , kvm@vger.kernel.org, =?iso-8859-1?Q?Herv=E9?= Poussineau , Shannon Zhao , Anthony Perard , Liu Yuan , David Gibson , Andrzej Zaborowski , Jason Wang , Artyom Tarasenko , Riku Voipio , Fam Zheng , Eduardo Habkost , Corey Minyard , Amit Shah , Pavel Dovgalyuk , Stefan Weil , Xie Changlong , Alistair Francis , Peter Lieven , "Dr. David Alan Gilbert" , Greg Kurz , =?iso-8859-1?Q?Marc-Andr=E9?= Lureau , Alex Williamson , qemu-arm@nongnu.org, Peter Chubb , Yuval Shaia , Stefan Hajnoczi , Paolo Bonzini , xen-devel@lists.xenproject.org, John Snow , Richard Henderson , Kevin Wolf , qemu-block@nongnu.org, Peter Crosthwaite , Hitoshi Mitake , Wen Congyang , qemu-s390x@nongnu.org, Cornelia Huck , "Richard W.M. Jones" , Juan Quintela , Max Reitz , Michael Walle , qemu-ppc@nongnu.org, Andreas =?iso-8859-1?Q?F=E4rber?= , Igor Mammedov , Hannes Reinecke , Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= On Wed, Mar 21, 2018 at 03:19:22PM +0000, Daniel P. Berrang=E9 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 of > > 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 - w= ill > > 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 This is exactly what this patch proposes, with a uniform scheme: start everything with qemu/. >=20 > > As another example of problems, a header by the same name in the sour= ce > > 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. We can not know that there are no system headers that start with block/ o= n any current or future systems. > > Let's change the scheme: make sure all headers that are not > > in the source directory are included through a path > > starting with qemu/ , thus: > >=20 > > #include <> > >=20 > > headers in the same directory as source are included with > >=20 > > #include "" > >=20 > > as per standard. >=20 > As stated before, I consider this a step backwards - it is a > good clear standard to use "" for project local includes and > <> for 3rd party / system includes IMHO. The change doesn't > do anything beneficial for the two scenarios described above > AFAICT. I think you are mistaken on the last point: 1. Everything will be under qemu/ so we never clash with a system file 2. A local stale file anywhere in source directory is completely ignored since source is not on -I path. I hope this clarifies things. >=20 > Regards, > Daniel > --=20 > |: https://berrange.com -o- https://www.flickr.com/photos/dberr= ange :| > |: https://libvirt.org -o- https://fstop138.berrange= .com :| > |: https://entangle-photo.org -o- https://www.instagram.com/dberr= ange :|