Re: perl_5.32.0~rc1-1 FTBFS on m68k (experimental)

[Geert Uytterhoeven <geert@linux-m68k.org>]

Hi Adrian,

On Thu, Jun 18, 2020 at 10:46 PM John Paul Adrian Glaubitz
<glaubitz@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.

Gr{oetje,eeting}s,

                        Geert


--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@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