Re: [Qemu-trivial] [Qemu-devel] [PATCH] hw/xen/xen_pvdev: Include qemu/log.h for qemu_log_vprintf()

[Peter Maydell]

On 2 November 2016 at 17:34, Stefano Stabellini <address@hidden> wrote:
> On Wed, 2 Nov 2016, Thomas Huth wrote:
>> Olaf Hering reported a build failure due to an undefined reference
>> to 'qemu_log_vprintf'. Explicitely including qemu/log.h seems to
>> fix the issue.
>>
>> Signed-off-by: Thomas Huth <address@hidden>
>
> The fix makes sense:
>
> Acked-by: Stefano Stabellini <address@hidden>
>
> However I was unable to reproduce the build failure, so I would like a
> confirmation from Olaf that the fix is working.

If you configure with the (default) simple trace
backend then trace.h will pull in qemu/log.h
(and in this case trace.h comes in via xen_common.h).
But if you're using a different backend then it won't
bring in that header, and you'll get the build failure.

This is a fairly common "breaks but only with
some trace backends" compile failure, but I'm
not sure how best to try to make it more robust
(or at least into a 'fails-everywhere' bug).

thanks
-- PMM