Hi Adrian,
On Fri, Jun 19, 2020 at 10:20 AM John Paul Adrian Glaubitz
<glaub...@physik.fu-berlin.de> wrote:
> > On Jun 19, 2020, at 10:02 AM, Geert Uytterhoeven <ge...@linux-m68k.org>
> > wrote:
> >> On Thu, Jun 18, 2020 at 10:46 PM John Paul Adrian Glaubitz
> >> <glaub...@physik.fu-berlin.de> wrote:
> >>> On 6/18/20 12:10 PM, John Paul Adrian Glaubitz wrote:
> >>> Reported upstream [1].
> >>
> >> It's an alignment issue and can be trivially fixed with this patch:
> >>
> >> diff --git a/op.h b/op.h
> >> index fc21f03cda..480c95245b 100644
> >> --- a/op.h
> >> +++ b/op.h
> >> @@ -698,7 +698,7 @@ struct opslot {
> >> U16 opslot_size; /* size of this slot (in pointers) */
> >> U16 opslot_offset; /* offset from start of slab (in ptr
> >> units) */
> >> OP opslot_op; /* the op itself */
> >> -};
> >> +} __attribute__ ((aligned (4)));
> >>
> >> struct opslab {
> >> OPSLAB * opslab_next; /* next slab */
> >
> > In the mean time, you changed this to add explicit padding instead:
> >
> > https://github.com/Perl/perl5/issues/17871
> >
> >> diff --git a/op.h b/op.h
> >> index fc21f03cda..fb9f538e23 100644
> >> --- a/op.h
> >> +++ b/op.h
> >> @@ -714,6 +714,7 @@ struct opslab {
> >> # ifdef PERL_DEBUG_READONLY_OPS
> >> bool opslab_readonly;
> >> # endif
> >> + U16 opslab_padding; /* padding to ensure
> >> proper alignment */
> >> OPSLOT opslab_slots; /* slots begin here */
> >> };
> >
> > I take it PERL_DEBUG_READONLY_OPS is enabled?
> > Hence the padding should be moved inside the #ifdef,
> > Furthermore, sizeof(bool) = 1, right? So you still have an implicit
> > hole, and it would be better to add 3 bytes of explicit padding
> > instead one 16-bit quantity.
>
> No, I didn’t take that #ifdef into consideration.
>
> And I’m confused now.
>
> Add the three bytes how? Inside the #ifdef makes no sense as that wouldn’t
> fix release builds.
So release builds fail, too?
And they don't set PERL_DEBUG_READONLY_OPS?
If PERL_DEBUG_READONLY_OPS is not set, I see no reason why
the padding would be needed.
Disclaimer: looking at the 5.26 version from Ubuntu, as github seems
to be down.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
