Re: [Xen-devel] Clang/LLVM version requirements

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2012-09-13 at 16:09 +0100, Keir Fraser wrote:
> On 13/09/2012 16:05, "Keir Fraser" <keir.xen@xxxxxxxxx> wrote:
> 
> > On 13/09/2012 15:55, "Tim Deegan" <tim@xxxxxxx> wrote:
> > 
> >> At 15:01 +0100 on 13 Sep (1347548504), Jan Beulich wrote:
> >>>>>> On 13.09.12 at 14:21, Tim Deegan <tim@xxxxxxx> wrote:
> >>>> Allowing BSS would just need a few extra runes (AFAICS,
> >>>> "--set-section-flags .bss=alloc,load,contents") in the objcopy that
> >>>> makes reloc.bin.
> >>>>  But I'm not sure how to make sure everything is
> >>>> rip-relative, do if that's the real concern I'm inclined to go with
> >>>> this compile-time check and exclude .[ro]data[.*] as well.
> >>>> We can always fix it up to allow bss and data sections if we ever
> >>>> actually need them.
> >>> 
> >>> As said, I'm fine with any approach as long as it works with all
> >>> supported tool chains. So feel free to go the route you're
> >>> proposing.
> >> 
> >> OK.  The patch below works for me on gccs 4.1 to 4.7 and clang 3.0.
> >> I tries gcc 3.4 but the build already fails in a few other places.
> >> Do we really still support gcc 3.4 like the README says?
> > 
> > It's been a long while since we updated our compiler support. In general
> > I've been happy to say we support each gcc release only for 2-3 years. In
> > this case that would mean we could *even* update our support to be only gcc
> > 4.2 and later.
> > 
> > What do people think about us forcing this? It might even let us get rid of
> > GCC_HAS_VISIBILITY_ATTRIBUTE?
> 
> I should add, this is mainly a question of how aggressive we should be. I'm
> quite happy to retire gcc-3.4 support if it happens it is now broken. In
> that case, x86/Rules.mk should have its gcc version check updated. And
> perhaps arch/arm may as well do the same? I would be happy to Ack a patch to
> that effect.

Some data points: Debian Squeeze (current stable) has gcc 4.4 as the
default (but ships a bunch of others) and Lenny (previous stable) had
4.3. AFAICT RHEL5 and SLES10 both shipped 4.1, SLES11 shipped 4.3 and
RHEL 6 4.4.

Do we really want/need to support host OSes older than RHEL5/SLES10? We
are talking 2006/7 vintage there.

Ian.


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