ELF: Check ELF_COMMON_DEF_P for common symbols

Since common symbols that are turned into definitions don't have the
DEF_REGULAR flag set, we need to check ELF_COMMON_DEF_P for common
symbols.

bfd/

	PR ld/19579
	PR ld/21306
	* elf32-s390.c (elf_s390_finish_dynamic_symbol): Check
	ELF_COMMON_DEF_P for common symbols.
	* elf64-s390.c (elf_s390_finish_dynamic_symbol): Likewise.
	* elf64-x86-64.c (elf_x86_64_relocate_section): Likewise.
	* elflink.c (_bfd_elf_merge_symbol): Revert commits
	202ac193bbbecc96a4978d1ac3d17148253f9b01 and
	07492f668d2173da7a2bda3707ff0985e0f460b6.

ld/

	PR ld/19579
	PR ld/21306
	* testsuite/ld-elf/pr19579a.c (main): Updated.

bfd/ChangeLog

@@ -1,3 +1,15 @@
+2017-04-07  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR ld/19579
+	PR ld/21306
+	* elf32-s390.c (elf_s390_finish_dynamic_symbol): Check
+	ELF_COMMON_DEF_P for common symbols.
+	* elf64-s390.c (elf_s390_finish_dynamic_symbol): Likewise.
+	* elf64-x86-64.c (elf_x86_64_relocate_section): Likewise.
+	* elflink.c (_bfd_elf_merge_symbol): Revert commits
+	202ac193bbbecc96a4978d1ac3d17148253f9b01 and
+	07492f668d2173da7a2bda3707ff0985e0f460b6.
+
 2017-04-07  Pedro Alves  <palves@redhat.com>
 
 	* opncls.c (bfd_get_debug_link_info): Rename to...

bfd/elf32-s390.c

@@ -3785,7 +3785,7 @@ elf_s390_finish_dynamic_symbol (bfd *output_bfd,
 	     RELATIVE reloc.  The entry in the global offset table
 	     will already have been initialized in the
 	     relocate_section function.  */
-	  if (!h->def_regular)
+	  if (!(h->def_regular || ELF_COMMON_DEF_P (h)))
 	    return FALSE;
 	  BFD_ASSERT((h->got.offset & 1) != 0);
 	  rela.r_info = ELF32_R_INFO (0, R_390_RELATIVE);

bfd/elf64-s390.c

@@ -3582,7 +3582,7 @@ elf_s390_finish_dynamic_symbol (bfd *output_bfd,
 	     RELATIVE reloc.  The entry in the global offset table
 	     will already have been initialized in the
 	     relocate_section function.  */
-	  if (!h->def_regular)
+	  if (!(h->def_regular || ELF_COMMON_DEF_P (h)))
 	    return FALSE;
 	  BFD_ASSERT((h->got.offset & 1) != 0);
 	  rela.r_info = ELF64_R_INFO (0, R_390_RELATIVE);

bfd/elf64-x86-64.c

@@ -4926,7 +4926,8 @@ do_ifunc_pointer:
 		{
 		  /* Symbol is referenced locally.  Make sure it is
 		     defined locally or for a branch.  */
-		  fail = !h->def_regular && !branch;
+		  fail = (!(h->def_regular || ELF_COMMON_DEF_P (h))
+			  && !branch);
 		}
 	      else if (!(bfd_link_pie (info)
 			 && (h->needs_copy || eh->needs_copy)))

bfd/elflink.c

@@ -1544,16 +1544,13 @@ _bfd_elf_merge_symbol (bfd *abfd,
      represent variables; this can cause confusion in principle, but
      any such confusion would seem to indicate an erroneous program or
      shared library.  We also permit a common symbol in a regular
-     object to override a weak symbol in a shared object.  A common
+     object to override a weak symbol in a shared object.  */
-     symbol in executable also overrides a symbol in a shared object.  */
 
   if (newdyn
       && newdef
       && (olddef
 	  || (h->root.type == bfd_link_hash_common
-	      && (newweak
+	      && (newweak || newfunc))))
-		  || newfunc
-		  || (!olddyn && bfd_link_executable (info))))))
     {
       *override = TRUE;
       newdef = FALSE;

ld/ChangeLog

@@ -1,3 +1,9 @@
+2017-04-07  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR ld/19579
+	PR ld/21306
+	* testsuite/ld-elf/pr19579a.c (main): Updated.
+
 2017-04-07  Nick Clifton  <nickc@redhat.com>
 
 	PR 21090

ld/testsuite/ld-elf/pr19579a.c

@@ -9,7 +9,7 @@ extern int *bar_p (void);
 int
 main ()
 {
-  if (foo[0] == 0 && foo == foo_p () && bar[0] == 0 && bar == bar_p ())
+  if (foo[0] == 0 && foo == foo_p () && bar[0] == -1 && bar == bar_p ())
     printf ("PASS\n");
   return 0;
 }