Re: weird padding in linux/timex.h, struct timex

[Muli Ben-Yehuda <mulix@actcom.co.il>]

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On Tue, Aug 06, 2002 at 02:36:04PM +0100, Alan Cox wrote:
> On Tue, 2002-08-06 at 12:15, Muli Ben-Yehuda wrote:
> > Hi, 
> > 
> > struct timex in include/linux/timex.h is defined as 
> > 
> > struct timex 
> > {
> > 	...
> > 	int  :32; int  :32; int  :32; int  :32;
> > 	int  :32; int  :32; int  :32; int  :32;
> > 	int  :32; int  :32; int  :32; int  :32;
> > }; 
> > 
> > I assume that this is used as padding. Is there any reason for using
> > bitfields as padding? If there is, a comment to that effect would be
> > nice. If there isn't, the following patch makes the padding explicit. 
> > 
> 
> That is how the interface has always been defined. I think we inherited
> that from the world of xntpd but I may be wrong. Your __pad is not
> always the same thing - you assume 4 byte ints and ints aligned the same
> way as char [], which may not always be true.

I assume 4 byte ints, because I assume that the length of a 32 bit
bitfield will be 32 bits. As for alignment, you're correct. 

I guess my question becomes: is the original code defined in any
special way, in regards to padding and size? If it isn't, my __pad
patch would be cleaner and just as correct in principle. If it is, I
can make a __pad which will behave exactly the same way. 

Thanks, Muli. 
-- 
I am PINK, hear me ROAR

http://vipe.technion.ac.il/~mulix/
http://syscalltrack.sf.net/

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