From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47183) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eyfWy-00076s-3D for qemu-devel@nongnu.org; Wed, 21 Mar 2018 11:20:03 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eyfWw-00059J-8T for qemu-devel@nongnu.org; Wed, 21 Mar 2018 11:20:00 -0400 Date: Wed, 21 Mar 2018 15:19:22 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Message-ID: <20180321151922.GR8551@redhat.com> Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= References: <1521642402-197739-1-git-send-email-mst@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1521642402-197739-1-git-send-email-mst@redhat.com> Subject: Re: [Qemu-devel] [PATCH v2] qemu: replace "" with <> in headers List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" 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, =?utf-8?B?SGVydsOp?= 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 , =?utf-8?Q?Marc-Andr=C3=A9?= 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 =?utf-8?Q?F=C3=A4rber?= , Igor Mammedov , Hannes Reinecke , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= 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. > > 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. > > Thus, for example, a system header trace.h - should it be present - will > conflict with our local trace.h If our local "trace.h" is in the current directory, then using "" is right and you can still use to get the system version. 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 "" 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. > As another example of problems, a header by the same name in the source > directory will always be picked up first - before any headers in > the include directory. 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. > 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: > > #include <> > > headers in the same directory as source are included with > > #include "" > > as per standard. 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. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|