Re: [PATCH] lto: Set resolution to LDPR_PREVAILING_DEF for non-IR common symbol

On Thu, Aug 27, 2026 at 10:28 PM Jan Beulich <[email protected]> wrote:
>
> On 27.08.2026 14:04, H.J. Lu wrote:
> > On Thu, Aug 27, 2026 at 7:52 PM Jan Beulich <[email protected]> wrote:
> >>
> >> On 27.08.2026 10:31, H.J. Lu wrote:
> >>> Since size or alignment of common symbol may be overridden by another
> >>> common symbol, set symbol resolution to LDPR_PREVAILING_DEF, instead of
> >>> LDPR_RESOLVED_EXEC, for common symbol in regular object when seeing an
> >>> undefined or common symbol from an IR object.
> >>
> >> Is this correct for the LDPK_COMMON case that's also covered by the if()
> >> that you alter in get_symbols()?
> >
> > My patch covers the case of
> >
> > syms[n].def == LDPK_COMMON && blhe->type == bfd_link_hash_common.
> >
> > which wasn't handled before.
>
> Right, but that doesn't answer my question, hinting towards a situation where
> two instances of a common symbol collide. And I can't really resolve that for
> myself because ...
>
> >> Adding to the (my?) confusion is that after said
> >>
> >>       if (syms[n].def == LDPK_UNDEF
> >>           || syms[n].def == LDPK_WEAKUNDEF
> >>           || syms[n].def == LDPK_COMMON)
> >>

It has everything to do with

     if (syms[n].def == LDPK_UNDEF
          || syms[n].def == LDPK_WEAKUNDEF
          || syms[n].def == LDPK_COMMON)

In its else clause, syms[n].def is LDPK_DEF or LDPK_WEAKDEF.
Linker plugin tells linker that originally def, weakdef, or common,
has been pre-empted.

> >> there's an "else if" with this comment:
> >>
> >>       /* Was originally def, weakdef, or common, but has been pre-empted.  */
> >>
> >> With the cited if(), no originally common symbol can make it there, can it?
>
> ... there's this comment which irritates me.
>
> > My patch covers
> >
> >       if (syms[n].def == LDPK_UNDEF
> >           || syms[n].def == LDPK_WEAKUNDEF
> >           || syms[n].def == LDPK_COMMON)
> >         {
> >              ...
> >
> > It has nothing to do with the else clause.
>
> Correct, and I didn't mean to say anything to the contrary.
>
> Jan



-- 
H.J.