Re: [PATCH v8 1/3] y2038: Introduce internal for glibc struct __timespec64

[Lukasz Majewski <lukma at denx dot de>]

Hi Florian,

> * Lukasz Majewski:
> 
> >> Regarding the actual patch, I don't understand why tv_pad isn't an
> >> *anonymous* bit field.   
> >
> > The reason for this is that we may need to clear this padding if we
> > plan to fix some issues - for example in kernel 5.1.0 - 5.1.4 there
> > is a bug for x32 which may require explicit clearing the padding.  
> 
> I think we cannot support those kernels with reasonable effort.  So
> cross-architecture source compatibility with existing practices is
> more important.

I see your point.

> 
> Furthermore, I think the consensus for the public struct timespec64 is
> that it should use an unnamed bitfield because of the prevalence of
> incorrect (according to POSIX) initializers.

Yes. Correct.

> 
> >> This seems to introduce unnecessary variance
> >> between architectures and is incompatible with how glibc itself
> >> uses struct timespec.   
> >
> > The v3 of this patch had this field defined as anonymous padding.
> > However, there was strong objection for such approach [1].  
> 
> > Links:
> > [1] - https://sourceware.org/ml/libc-alpha/2019-05/msg00151.html  
> 
> The patch has a named bitfield:
> 
> +  int tv_pad: 32;            /* Padding named for checking/setting */
> 

Ach. Yes indeed - there was a _named_ bitfield in the patch. 

> As far as I can see, the discussion was about what was actually in the
> patch, and not an unnamed bitfield.

Yes, you seems to be right. Andreas objection was about the bitfield
usage.


Let's wait for Joseph's opinion if we shall replace named padding struct
members with unnamed bitfields (and drop potential support for fixing
issues, which would require explicit clearing of padding before passing
data to the kernel). 


Best regards,

Lukasz Majewski

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