[PING PATCH, PR 57748] Set mode of structures with zero sized arrays to be BLK

[Jakub Jelinek]

On Tue, Aug 27, 2013 at 04:03:42PM +0200, Martin Jambor wrote:
> On Fri, Aug 23, 2013 at 05:29:23PM +0200, Jakub Jelinek wrote:
> > On Fri, Aug 23, 2013 at 05:11:22PM +0200, Martin Jambor wrote:
> > > Hi Jakub and/or Joseph,
> > > 
> > > the reporter of this bug seems to be very anxious to have it fixed in
> > > the repository.  While Richi is away, do you think you could have a
> > > look?  It is very small.
> > 
> > Isn't this ABI incompatible change (at least potential on various targets)?
> > If so, then it shouldn't be applied to release branches, because it would
> > create (potential?) ABI incompatibility between 4.8.[01] and 4.8.2.
> > 
> 
> I don't know.  I did a few attempts to observe a change in the calling
> convention of a function accepting a zero sized array terminated
> structure by value (on x86_64) but I did not succeed.  On the other
> hand, I assume there are many other ways how a mode can influence ABI.
> So I'll try to have a look whether we can hack around this situation
> in 4.8's expr.c instead.

All I remember that e.g. the number of regressions from PR20020 was big,
and any kind of TYPE_MODE changes are just extremely risky.
Perhaps x86_64 in the ABI decisions never uses mode, but we have tons of
other targets and it would surprise me if none of those were affected.

> Nevertheless, is this patch ok for trunk?

I'll defer that to Richard now that he is back ;)

	Jakub