Re: [PATCH] tools: libxc: do not redefine evtchn_port_or_error_t in xc_evtchn_compat.c

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 04/02/16 10:19, Ian Campbell wrote:
> Adding Olaf, I forgot that Reported-by doesn't turn into a Cc.
>
> On Thu, 2016-02-04 at 10:15 +0000, Ian Campbell wrote:
>> This file stradles the xenevtchn and libxc evtchn_compat worlds, and
>> hence ends up with two evtchn_port_or_error_t typedefs which older
>> gcc's (and the C standard) do not like.
>>
>> Avoid this by gating the compat definition on a gate provided by the
>> compat implementation.
>>
>> Note that this would still be broken by an application which does:
>>     #define XC_WANT_COMPAT_EVTCHN_API
>>     #include <xenevtchn.h>
>>     #include <xenctrl.h>
>>
>> Which effectively means that an application must be ported over to
>> xenevtchn in one go rather than incrementally (e.g. if it uses
>> evtchn's for multiple purposes). Since the port is actually fairly
>> mechanical I hope this is acceptable.
>>
>> Reported-by: Olaf Hering <olaf@aepfle.de>
>> Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
>> Cc: Andrew Cooper <andrew.cooper3@citrix.com>
>> ---
>> I'm not super happy about this approach, due to the caveat in the
>> second half of the commit message.
>>
>> Other approaches:
>>
>> rename the libxenevtchn type, e.g.  xenevtchn_port_or_error_t?
> Thinking about this some more this might be the best approach. The type is
> not used by qemu-xen, it is used by qemu-xen-traditional but we can fix
> that in lockstep.
>
> All of the in tree users are easy, of course.
>
> Thoughts?

Thinking about it, this looks like a better option.  It is also more in
line with the library naming.

~Andrew