Re: [Xen-devel] [PATCH 1/4] interface: avoid redefinition of __XEN_INTERFACE_VERSION__

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 28.02.17 at 13:24, <JGross@xxxxxxxx> wrote:
> On 28/02/17 12:11, Jan Beulich wrote:
>>>>> On 28.02.17 at 11:34, <JGross@xxxxxxxx> wrote:
>>> In stubdom environment __XEN_INTERFACE_VERSION__ is sometimes defined
>>> on the command line of the build instruction. This conflicts with
>>> xen-compat.h defining it unconditionally if __XEN__ or __XEN_TOOLS__
>>> is set.
>> 
>> Then that's what wants fixing. In fact it's questionable whether
>> __XEN_TOOLS__ (or even __XEN__) getting defined there is
>> appropriate.
> 
> There are multiple libraries from the tools directory being compiled
> for stubdoms.

Each if which should get appropriate settings.

>>> Just use #undef in this case to avoid the resulting warning.
>> 
>> I think the lack of a warning in case of a collision is worse here.
>> People should simply not define both the version symbol and
>> either of __XEN__ or __XEN_TOOLS__.
> 
> Would you be okay with:
> 
> #if defined(__XEN_INTERFACE_VERSION__)
>   #if __XEN_INTERFACE_VERSION__ != __XEN_LATEST_INTERFACE_VERSION__
>     #error ...
>   #endif
> #else
>   #define __XEN_INTERFACE_VERSION__ __XEN_LATEST_INTERFACE_VERSION__
> #endif

Well - see Ian's reply. If the values match (granted textually rather
than by value), there should be no compiler warning in the first
place.

Jan


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