[Bug gold/19842] LTO build fails to write call address for weak symbol reference

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=19842

H.J. Lu <hjl.tools at gmail dot com> changed:

           What    |Removed                     |Added
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                 CC|                            |amodra at gmail dot com

--- Comment #18 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to Cary Coutant from comment #17)
> > For ld, non-LTO definition takes precedence over LTO one.
> 
> What symbol resolution does ld tell the compiler for the LTO
> definition? The LTO design was intended to preserve the same binding
> order that would have been observed in a non-LTO build (to the extent
> possible). Try your example without -flto at all.
> 
> If ld tells the compiler that the LTO definition is PREVAILING_DEF, it
> will provide a new definition, but not in a COMDAT group. But that
> definition won't be WEAK, so the order wouldn't matter and it should
> still bind to the LTO definition. That suggests to me that ld is
> telling it that the LTO definition is PREEMPTED_REG. But that doesn't
> preserve the expected binding order.

commit 3a5dbfb2502e7a49422f13c9cec2becfd46f44f1
Author: Alan Modra <address@hidden>
Date:   Tue Jun 21 14:55:26 2011 +0000

      * elflink.c (_bfd_elf_merge_symbol): Allow type changes for
      plugin symbols.  Fix segfault on linker scrip defined syms.

has

  /* Skip weak definitions of symbols that are already defined.  */
  if (newdef && olddef && newweak)
    {
      /* Don't skip new non-IR weak syms.  */
      if (!(oldbfd != NULL
            && (oldbfd->flags & BFD_PLUGIN) != 0
            && (abfd->flags & BFD_PLUGIN) == 0))
        {
          newdef = FALSE;
          *skip = TRUE; 
        }

which prefers regular definition over definition in IR.

> (Does ld *ever* say an LTO symbol is PREVAILING_DEF?)

Yes.

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