[Bug ld/26256] Support mixed SHF_LINK_ORDER & non-SHF_LINK_ORDER components in an output section

[i at maskray dot me]

https://sourceware.org/bugzilla/show_bug.cgi?id=26256

--- Comment #15 from Fangrui Song <i at maskray dot me> ---
(In reply to H.J. Lu from comment #14)
> (In reply to Fangrui Song from comment #13)
> > (In reply to H.J. Lu from comment #12)
> > > (In reply to Fangrui Song from comment #10)
> > > > (In reply to H.J. Lu from comment #8)
> > > > > Created attachment 13070 [details]
> > > > > A patch with tests
> > > > > 
> > > > > Try this.
> > > > 
> > > > With a minor change, it'll match LLD (I place ordered sections before
> > > > unordered sections because Solaris folks said they did so).
> > > > 
> > > > +      /* Place ordered sections before unordered sections.  */
> > > > +      if (bsec != NULL)
> > > > +       return 1;
> > > > +      else if (asec != NULL)
> > > > +       return -1;
> > > > +      return 0;
> > > > 
> > > > For the test case lld/test/ELF/linkorder-mixed.s , ld-new produced %t, 
> > > > %t1
> > > > and %t3 now match LLD.
> > > > %t2 and %t4 still don't, but they are probably corner cases and don't 
> > > > matter
> > > > in practice.
> > > 
> > > %t2 and %t4 are lld specific behavior.
> > 
> > 
> > I actually think %t2 and %t4 are generic: ordered .rodata.bar (.byte 3)
> > precedes unordered .rodata.bar (.byte 2)
> > 
> >   SECTIONS { .rodata : {*(.rodata.foo) *(.rodata.bar)} }
> > 
> > What LLD does is to perform SHF_LINK_ORDER sorting within the input section
> > description *(.rodata.bar). I agree that this is a corner case which can
> > hardly do harm in practice.
> 
> It is a bug:
> 
> diff --git a/bfd/elflink.c b/bfd/elflink.c
> index a1e4635e96..ddff3bfe7b 100644
> --- a/bfd/elflink.c
> +++ b/bfd/elflink.c
> @@ -11988,9 +11988,7 @@ elf_fixup_link_order (struct bfd_link_info *info,
> bfd *abfd, asection *o)
>    for (p = o->map_head.link_order; p != NULL; p = p->next)
>      sections[seen_linkorder++] = p;
>  
> -  for (indirect_sections = sections, n = 0;
> -       n < seen_linkorder;
> -       indirect_sections++, n++)
> +  for (indirect_sections = sections, n = 0; n < seen_linkorder;)
>      {
>        /* Find the first bfd_indirect_link_order section.  */
>        if (indirect_sections[0]->type == bfd_indirect_link_order)
> @@ -12012,6 +12010,11 @@ elf_fixup_link_order (struct bfd_link_info *info,
> bfd *abfd, asection *o)
>      indirect_sections += n_indirect;
>      n += n_indirect;
>    }
> +      else
> +  {
> +    indirect_sections++;
> +    n++;
> +  }
>      }

Thanks. With this diff added, all the %t* tests are good now.

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