Linux Virtualization - Sep 2014 - [Qemu-devel] [PATCH 1/2] virtio-gpu/2d: add hardware spec include file

On Sun, Sep 14, 2014 at 07:04:11AM -0700, Peter Maydell
wrote:
> On 14 September 2014 06:46, Michael S. Tsirkin <mst at redhat.com>
wrote:
> > BUILD_BUG_ON in linux, QEMU_BUILD_BUG_ON in QEMU.
> > You have to stick it in a C file though, so it
> > won't be visible in this patch.
> 
> Why do you think that? We have several header files which
> use QEMU_BUILD_BUG_ON and I don't see any reason why
> it would have to be invoked from a .c file.
> 
> -- PMM
Because Gerd wants to share this with linux uapi, and
you can't use BUILD_BUG_ON in uapi headers on linux.

On 14 September 2014 07:11, Michael S. Tsirkin <mst at redhat.com>
wrote:
> On Sun, Sep 14, 2014 at 07:04:11AM -0700, Peter Maydell wrote:
>> On 14 September 2014 06:46, Michael S. Tsirkin <mst at
redhat.com> wrote:
>> > BUILD_BUG_ON in linux, QEMU_BUILD_BUG_ON in QEMU.
>> > You have to stick it in a C file though, so it
>> > won't be visible in this patch.
>>
>> Why do you think that? We have several header files which
>> use QEMU_BUILD_BUG_ON and I don't see any reason why
>> it would have to be invoked from a .c file.
> Because Gerd wants to share this with linux uapi, and
> you can't use BUILD_BUG_ON in uapi headers on linux.
Who owns the "master" copy of the header and commits
to making sure it builds on other things than Linux+gcc
in that case?

-- PMM

On Sun, Sep 14, 2014 at 07:32:21AM -0700, Peter Maydell
wrote:
> On 14 September 2014 07:11, Michael S. Tsirkin <mst at redhat.com>
wrote:
> > On Sun, Sep 14, 2014 at 07:04:11AM -0700, Peter Maydell wrote:
> >> On 14 September 2014 06:46, Michael S. Tsirkin <mst at
redhat.com> wrote:
> >> > BUILD_BUG_ON in linux, QEMU_BUILD_BUG_ON in QEMU.
> >> > You have to stick it in a C file though, so it
> >> > won't be visible in this patch.
> >>
> >> Why do you think that? We have several header files which
> >> use QEMU_BUILD_BUG_ON and I don't see any reason why
> >> it would have to be invoked from a .c file.
> 
> > Because Gerd wants to share this with linux uapi, and
> > you can't use BUILD_BUG_ON in uapi headers on linux.
> 
> Who owns the "master" copy of the header and commits
> to making sure it builds on other things than Linux+gcc
> in that case?
> 
> -- PMM
For most of virtio neither linux nor QEMU are the master.
syncing them has been done manually in the past.
As we are copying other headers from Linux anyway,
I think it would be better for everyone if we make
the Linux headers the master for QEMU going forward.

-- 
MST

Hi,
> >>
> >> Why do you think that? We have several header files which
> >> use QEMU_BUILD_BUG_ON and I don't see any reason why
> >> it would have to be invoked from a .c file.
> 
> > Because Gerd wants to share this with linux uapi, and
> > you can't use BUILD_BUG_ON in uapi headers on linux.
> 
> Who owns the "master" copy of the header and commits
> to making sure it builds on other things than Linux+gcc
> in that case?
In my personal repo the master copy is in the linux tree and qemu gets
synced.  I've placed the QEMU_BUILD_BUG_ON calls in the (qemu-only)
virtio-gpu.c now.

cheers,
  Gerd