[Xen-devel] Re: [PATCH 2/6] trace: fix T_INFO_FIRST_OFFSET

[George Dunlap <george.dunlap@xxxxxxxxxxxxx>]

Jan Beulich wrote:
> That part your patch doesn't address either - rather than
> sizeof(uint16_t) as the first part of the expression you'd need to
> use sizeof(struct t_info) or offsetof(struct t_info, mfn_offset).
>   
I was assuming that when someone changed struct t_info that they'd 
modify this macro as well; I suppose then that the two complaints are 
really different aspects of the same one -- that it might not be clear 
to the person who adjusts struct t_info how to translate those changes 
into T_INFO_FIRST_OFFSET.  I think this way is more clear.
I suppose even better might be to calculate 
t_info.mfn_mfn_offset[NR_CPUS] (or perhaps ...[num_possible_cpus]).  
Hmm... let me see what I can come up with.
> Btw., didn't we agree that public headers shouldn't make use of
> language extensions? struct t_info uses a variable sized array,
> which is an extension (standard only in C99).
>   
I'm not an expert in this.  It's lot more hassle to lay out the data the 
way I'd like without it.  I'll defer judgment to Keir.
-George

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