Re: [Xen-devel] [PATCH v6 03/14] xen: Use a typesafe to define INVALID_MFN

[Elena Ufimtseva <elena.ufimtseva@xxxxxxxxxx>]

On Fri, Jul 08, 2016 at 08:20:03PM +0100, Andrew Cooper wrote:
> On 08/07/2016 23:01, Elena Ufimtseva wrote:
> >
> >>> @@ -838,7 +838,6 @@ mfn_t oos_snapshot_lookup(struct domain *d, mfn_t 
> >>> gmfn)
> >>>
> >>>      SHADOW_ERROR("gmfn %lx was OOS but not in hash table\n", 
> >>> mfn_x(gmfn));
> >>>      BUG();
> >>> -    return _mfn(INVALID_MFN);
> > Can compiler be unhappy about this?
> 
> This was my suggestion, from a previous round of review.

Ah! Thanks for explanation.
> 
> A while ago, I annotated BUG() with unreachable(), as as execution will
> not continue from a bugframe, but the shadow code is definitely older
> than my change.
> 
> As such, compilers will have been dropping this return statement as part
> of dead-code-elimination anyway.
> 
> This option is better than just replacing one bit of dead code with a
> different bit of dead code.
> 
> ~Andrew

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