[patch bfd]: Adjust handling for plugin-generated sections for pe-coff targets

[Kai Tietz]

2011/10/6 Alan Modra <amodra@gmail.com>:
> On Tue, Oct 04, 2011 at 08:50:20AM -0400, NightStrike wrote:
>> Ping
>
> I've been away..
>
>> On Thu, Sep 29, 2011 at 4:56 AM, Kai Tietz <ktietz70@googlemail.com> wrote:
>> > 2011/9/29 Alan Modra <amodra@gmail.com>:
>> >> I think this is wrong.  You should never be applying a relocation
>> >> against a symbol defined in an IR section.  If you are, then either ld
>> >> has failed to redefine the symbol properly when given a real
>> >> definition in LTO output, or gcc has failed to supply the real
>> >> definition.  Either way, you shouldn't hide this error.
>> >
>> > Well, it might be wrong, if we assume that all objects are seen by IR.
>> >  That isn't the case for now.  By this it happens (I can sent you test
>> > for this issue offline - it is a bit too big and complex to do for it
>> > a binutils testcase, if you are intetested) in cases that within a
>> > used library the same object (call it x) as additional specified on
>> > command-line is specified.  Here the object-file x on command-line
>> > gets resolved later, so that IR assumes it has an IRONLY symbol from
>> > its library version of x, but later on when the object x from
>> > command-line is finally linked, the IR version of x is getting
>> > discarded.  By this any function reference in library to a symbol of
>> > library's object x version, are pointing to discarded version,  This
>> > doesn't cause troubles, as on final linking the already linked
>> > object-references are used instead.  Actually they aren't
>> > multiple-times linked, just once.
>
> Your argument hasn't convinced me to approve your patch.  I still
> believe it is wrong to ignore *all* relocs against symbols defined in
> IR sections, as your patch does.  It might be reasonable to ignore
> some, as the ELF linker does for relocs in debug or other special
> handled sections.

Well, the point here is that we don't want to warn about discarded
sections here in some cases.  I see that we miss for non-IR sections
to check for finfo->info->strip_discarded, as this means we won't have
duplicates.  So a symbol from IR won't be written out (and here might
be another issue in write-symbol, too), and therefore it isn't double
defined.

Secondly it seems to be not correct to check here for EXCLUDED flag,
instead we should look always for section being no abs-one, and
output-section being an abs-section.
As if SEC_EXCLUDED is set, the output-section is always set to
abs-section.  So check logic is more equal to ELF.

Alter patch attached. I did a regression test for x86_64-w64-mingw32,
i686-w64-mingw, and i686-pc-cygwin.

Regards,
Kai

Index: cofflink.c
===================================================================
RCS file: /cvs/src/src/bfd/cofflink.c,v
retrieving revision 1.79
diff -u -r1.79 cofflink.c
--- cofflink.c	17 Aug 2011 00:39:38 -0000	1.79
+++ cofflink.c	8 Oct 2011 10:33:37 -0000
@@ -2380,13 +2391,23 @@
 	      while (h->root.type == bfd_link_hash_indirect
 		     || h->root.type == bfd_link_hash_warning)
 		h = (struct coff_link_hash_entry *) h->root.u.i.link;
+	      if ((h->root.type == bfd_link_hash_defined
+	           || h->root.type == bfd_link_hash_defweak)
+	          && ((finfo->info->strip_discarded
+	               && h->root.u.def.section != NULL
+	               && !bfd_is_abs_section (h->root.u.def.section)
+	               && bfd_is_abs_section (h->root.u.def.section->output_section))
+	              || (h->root.u.def.section->owner != NULL
+	                  && (h->root.u.def.section->owner->flags &
BFD_PLUGIN) != 0)))
+	         continue;
 	      if (h->root.type == bfd_link_hash_defined
 		  || h->root.type == bfd_link_hash_defweak)
 		ps = h->root.u.def.section;
 	      if (ps == NULL)
 		continue;
 	      /* Complain if definition comes from an excluded section.  */
-	      if (ps->flags & SEC_EXCLUDE)
+	      if (!bfd_is_abs_section (ps)
+	          && bfd_is_abs_section ((ps)->output_section))
 		(*finfo->info->callbacks->einfo)
 		  (_("%X`%s' referenced in section `%A' of %B: "
 		     "defined in discarded section `%A' of %B\n"),