Re: [PATCH 2/2] fix compilation with kvm disabled

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Jul 08, 2009 at 03:20:02PM +0300, Avi Kivity wrote:
> On 07/08/2009 03:13 PM, Michael S. Tsirkin wrote:
>>>> I think it's time we stopped worrying about builds against old kernel
>>>> headers or without them. What do we gain from it?
>>>>
>>>>        
>>> qemu upstream doesn't carry its own headers, so it we want to merge, we
>>> need to work against old headers.
>>>      
>>
>> Was there ever discussion on this? I think the right thing to do is to
>> add own headers to qemu upstream.
>>    
>
> Discussion yes, conclusion no.
>
>>>> I believe that the right thing to do is to define kvm_enabled as a macro
>>>> returning 0, and let compiler optimize the code out.
>>>>
>>>>        
>>> Doesn't work with -O0 (or if it does, we can't count on it).
>>>      
>>
>> With -O0 you get a ton of dead code anyway. Who cares
>
> People who debug (though -O1 works fine most of the time).  It also  
> feels unclean to rely on optimization for correctness.

I do not propoise to rely on optimization for correctness.
The code under if (0) will get compiled with -O0 (and we need to carry
our headers for this) but will never run.

-- 
MST