[PATCH] bfd: support section groups with preceding SHF_GROUP sections

[Jose E. Marchesi]

GAS always places section groups (SHT_GROUP) before the rest of the
sections in the output file.  However, other assemblers may place
section groups after the group members.

Example in the object attached, xdfdh.o:

COMDAT group section [   12] `.group.__cg_vis_memcpy' [__cg_vis_memcpy]
contains 1 sections:
   [Index]    Name
      [    4]   .text.__cg_vis_memcpy

Note how .text.__cg_vis_memcpy (idx 4) is placed before
.group.__cg_vis_memcpy (idx 12).

This is not handled properly by BFD.  The patch below makes sure to
create BFD sections for all the SHT_GROUP sections in the input file
before processing SHF_GROUP sections.

Tested in sparc64-linux-gnu and x86_64-linux-gnu.
No regressions.

PS: I looked into creating a test for this, but couldn't find a way to
    create such an object file with GAS, nor to reorder the sections.
    Adding a binary object to the LD testsuite is probably a no-no.  Any
    suggestion?


2017-06-05  Jose E. Marchesi  <jose.marchesi@oracle.com>

	* elf.c (setup_group): Make sure BFD sections are created for all
	group sections in the input file when processing SHF_GROUP
	sections.

diff --git a/bfd/elf.c b/bfd/elf.c
index 34d39c5..1cc0952 100644
--- a/bfd/elf.c
+++ b/bfd/elf.c
@@ -636,6 +636,11 @@ setup_group (bfd *abfd, Elf_Internal_Shdr *hdr, asection *newsect)
 		  unsigned char *src;
 		  Elf_Internal_Group *dest;
 
+                  /* Make sure the group section has a BFD section
+                     attached to it.  */
+                  if (!bfd_section_from_shdr (abfd, i))
+                    return FALSE;
+                  
 		  /* Add to list of sections.  */
 		  elf_tdata (abfd)->group_sect_ptr[num_group] = shdr;
 		  num_group += 1;

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