Re: [PATCH] elf: Remove zero-sized relocation section from section group

["H.J. Lu" <hjl.tools@gmail.com>]

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On Fri, Apr 3, 2020 at 6:56 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Fri, Apr 3, 2020 at 5:36 PM Alan Modra <amodra@gmail.com> wrote:
> >
> > On Fri, Apr 03, 2020 at 01:48:42PM -0700, H.J. Lu wrote:
> > > On Thu, Apr 2, 2020 at 9:45 PM Alan Modra <amodra@gmail.com> wrote:
> > > >
> > > > On Thu, Apr 02, 2020 at 08:41:18PM -0700, H.J. Lu via Binutils wrote:
> > > > > We must keep zero-sized relocation section in a section group.  Otherwise,
> > > > > the relocation section will be missing from the section group.
> > > >
> > > > Wouldn't it be better to get rid of these bogus relocation sections?
> > > > Should be possible with a change to _bfd_elf_fixup_group_sections, I
> > > > think.
> > >
> > > Here is the patch which does that.  OK for master?
> >
> > OK, thanks.
> >
> > Hmm, do we want a warning message?  I'm OK with it as a reminder to
>
> I will remove the warning.
>
> > people to fix their compilers and/or assembly, but other than that it
> > seems to me that removing an empty relocation section is hardly of
> > concern to users.  How was your testcase generated?
> >
>
> I was given an object file generated by an "unnamed" compiler :-).
> I have told them to fix their compiler.
>
> Thanks.

This is what I am checking in.

-- 
H.J.

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From fad689e7b5d92d50986ec040071e84b5eb50604f Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Thu, 2 Apr 2020 20:38:02 -0700
Subject: [PATCH] elf: Remove zero-sized relocation section from section group

Remove zero-sized relocation section from a section group since it has
been removed from the output.

	PR ld/25767
	* elf.c (_bfd_elf_fixup_group_sections): Remove zero-sized
	relocation section from section group.
---
 bfd/elf.c | 37 ++++++++++++++++++++++++++-----------
 1 file changed, 26 insertions(+), 11 deletions(-)

diff --git a/bfd/elf.c b/bfd/elf.c
index 86dadea05c..1780074f5a 100644
--- a/bfd/elf.c
+++ b/bfd/elf.c
@@ -7929,19 +7929,34 @@ _bfd_elf_fixup_group_sections (bfd *ibfd, asection *discarded)
 		elf_section_flags (s->output_section) &= ~SHF_GROUP;
 		elf_group_name (s->output_section) = NULL;
 	      }
-	    /* Conversely, if the member section is not being output
-	       but the SHT_GROUP section is, then adjust its size.  */
-	    else if (s->output_section == discarded
-		     && isec->output_section != discarded)
+	    else
 	      {
 		struct bfd_elf_section_data *elf_sec = elf_section_data (s);
-		removed += 4;
-		if (elf_sec->rel.hdr != NULL
-		    && (elf_sec->rel.hdr->sh_flags & SHF_GROUP) != 0)
-		  removed += 4;
-		if (elf_sec->rela.hdr != NULL
-		    && (elf_sec->rela.hdr->sh_flags & SHF_GROUP) != 0)
-		  removed += 4;
+		if (s->output_section == discarded
+		    && isec->output_section != discarded)
+		  {
+		    /* Conversely, if the member section is not being
+		       output but the SHT_GROUP section is, then adjust
+		       its size.  */
+		    removed += 4;
+		    if (elf_sec->rel.hdr != NULL
+			&& (elf_sec->rel.hdr->sh_flags & SHF_GROUP) != 0)
+		      removed += 4;
+		    if (elf_sec->rela.hdr != NULL
+			&& (elf_sec->rela.hdr->sh_flags & SHF_GROUP) != 0)
+		      removed += 4;
+		  }
+		else
+		  {
+		    /* Also adjust for zero-sized relocation member
+		       section.  */
+		    if (elf_sec->rel.hdr != NULL
+			&& elf_sec->rel.hdr->sh_size == 0)
+		      removed += 4;
+		    if (elf_sec->rela.hdr != NULL
+			&& elf_sec->rela.hdr->sh_size == 0)
+		      removed += 4;
+		  }
 	      }
 	    s = elf_next_in_group (s);
 	    if (s == first)
-- 
2.25.1