Re: [Qemu-ppc] [PATCH] qemu: include generated files with <> and not ""

From: "Michael S. Tsirkin" <mst@redhat.com>
To: Thomas Huth <thuth@redhat.com>
Cc: Peter Maydell <peter.maydell@linaro.org>,
	Dmitry Fleytman <dmitry.fleytman@gmail.com>,
	sheepdog@lists.wpkg.org,
	Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>,
	Li Zhijian <lizhijian@cn.fujitsu.com>,
	David Hildenbrand <david@redhat.com>,
	Jeff Cody <jcody@redhat.com>,
	Stefan Hajnoczi <stefanha@redhat.com>,
	qemu-devel@nongnu.org, BALATON Zoltan <balaton@eik.bme.hu>,
	Keith Busch <keith.busch@intel.com>,
	Max Filippov <jcmvbkbc@gmail.com>,
	Hannes Reinecke <hare@suse.com>,
	Gerd Hoffmann <kraxel@redhat.com>, Fam Zheng <famz@redhat.com>,
	Max Reitz <mreitz@redhat.com>, Eric Blake <eblake@redhat.com>,
	Josh Durgin <jdurgin@redhat.com>,
	Stefano Stabellini <sstabellini@kernel.org>,
	Alberto Garcia <berto@igalia.com>,
	zhanghailiang <zhang.zhanghailiang@huawei.com>,
	Ben Warren <ben@skyportsystems.com>,
	Stefan Berger <stefanb@linux.vnet.ibm.com>,
	Yongbok Kim <yongbok.kim@mips.com>,
	Michael R
Subject: Re: [Qemu-ppc] [PATCH] qemu: include generated files with <> and not ""
Date: Wed, 21 Mar 2018 15:08:36 +0200	[thread overview]
Message-ID: <20180321150543-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <459fa95d-8f0a-22fa-80fb-4af22ccf49b3@redhat.com>

On Wed, Mar 21, 2018 at 08:16:00AM +0100, Thomas Huth wrote:
> On 20.03.2018 13:05, Michael S. Tsirkin wrote:
> > On Tue, Mar 20, 2018 at 09:58:23AM +0100, Laurent Vivier wrote:
> >> Le 20/03/2018 à 02:54, Michael S. Tsirkin a écrit :
> >>> QEMU coding style at the moment asks for all non-system
> >>> include files to be used with #include "foo.h".
> >>> However this rule actually does not make sense and
> >>> creates issues for when the included file is generated.
> >>
> >> If you change that, we can have issue when a system include has the same
> >> name as our local include. With "<FILE>", system header are taken first.
> > 
> > Are you sure? I just tested and that is not the case with
> > either gcc or clang.
> > 
> >>> In C, include "file" means look in current directory,
> >>> then on include search path. Current directory here
> >>> means the source file directory.
> >>> By comparison include <file> means look on include search path.
> >>
> >> Not exactly, there is the notion of "system header" too.
> >>
> >> https://gcc.gnu.org/onlinedocs/cpp/Include-Syntax.html
> >>
> >> #include <file>
> >> This variant is used for system header files. It searches for a file
> >> named file in a standard list of system directories. You can prepend
> >> directories to this list with the -I option (see Invocation).
> > 
> > This is exactly what we do.
> > 
> >> #include "file"
> >> This variant is used for header files of your own program. It searches
> >> for a file named file first in the directory containing the current
> >> file, then in the quote directories and then the same directories used
> >> for <file>. You can prepend directories to the list of quote directories
> >> with the -iquote option.
> > 
> > Since we do not use -iquote, "" just adds the current directory.
> 
> So why don't we simply switch to use -iquote instead of -I for adding
> search paths for our own headers? We then would get a clean separation
> of QEMU headers from system headers.
> 
>  Thomas

It still leaves us with a host of problems e.g. the problem of stale
headers in the source directory.

-- 
MST

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