[patch] Restore .gnu.linkonce.r. g++-3.4 linking

[Jan Kratochvil <jan dot kratochvil at redhat dot com>]

Hi,

the attached testcase reproduces a regression of ld on the output of g++-3.4:

binutils-2.15.92.0.2:
`.gnu.linkonce.t.foo' referenced in section `.gnu.linkonce.r.foo' of
/tmp/2j.o: defined in discarded section `.gnu.linkonce.t.foo' of /tmp/2j.o
output produced  (.rela.gnu.linkonce.r.foo present with cleared relocations)

CVS HEAD:
`.gnu.linkonce.t.foo' referenced in section `.gnu.linkonce.r.foo' of
/tmp/2j.o: defined in discarded section `.gnu.linkonce.t.foo' of /tmp/2j.o
no output

patched CVS HEAD:
(no warnings)
output produced (.rela.gnu.linkonce.r.foo present with cleared relocations)


/* g++-3.x specific - before COMDAT groups were supported.  .gnu.linkonce.r.*
   is present only sometimes, depending on the compilation options.
   .gnu.linkonce.r.* is like .rodata for its .gnu.linkonce.t.* so there is no
   use for it if it did not exist in the file from which we chose
   .gnu.linkonce.t.* as the one not being discarded.  We would also fail to
   PRETEND the symbols as the other .gnu.linkonce.r.* section has different
   size.  */

g++-3.x introduced .gnu.linkonce.r.* by:
http://gcc.gnu.org/ml/gcc-patches/2004-08/msg00653.html

It would be best to discard such .gnu.linkonce.r.* section if its
.gnu.linkonce.t.* counterpart is discarded but I do not find it so important
as the whole patch is just for the temporary backward compatibility.
http://people.redhat.com/jkratoch/binutils-rbind.patch (best to be in g++-3.4)
http://people.redhat.com/jkratoch/binutils-rdiscard.patch

No regressions but the new testcase fails for (expected - as the other
linkonce* testcases also fail there due to the local label `1'):
hppa64-hp-hpux11.23 mmix-elf shl-unknown-netbsdelf1.6T


Thanks,
Jan


2008-10-22  Jan Kratochvil  <jan.kratochvil@redhat.com>

	Support pre-COMDAT g++-3.4 possibly missing `.gnu.linkonce.r.*'.
	* elflink.c (_bfd_elf_default_action_discarded <.gnu.linkonce.r.>): New.

2008-10-22  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* ld-elf/linkoncerdiff.d, ld-elf/linkoncerdiff1.s,
	ld-elf/linkoncerdiff2.s: New.

--- bfd/elflink.c	20 Oct 2008 10:57:33 -0000	1.315
+++ bfd/elflink.c	22 Oct 2008 21:50:58 -0000
@@ -8811,6 +8811,16 @@ _bfd_elf_default_action_discarded (asect
   if (strcmp (".gcc_except_table", sec->name) == 0)
     return 0;
 
+  /* g++-3.x specific - before COMDAT groups were supported.  .gnu.linkonce.r.*
+     is present only sometimes, depending on the compilation options.
+     .gnu.linkonce.r.* is like .rodata for its .gnu.linkonce.t.* so there is no
+     use for it if it did not exist in the file from which we chose
+     .gnu.linkonce.t.* as the one not being discarded.  We would also fail to
+     PRETEND the symbols as the other .gnu.linkonce.r.* section has different
+     size.  */
+  if (CONST_STRNEQ (sec->name, ".gnu.linkonce.r."))
+    return 0;
+
   return COMPLAIN | PRETEND;
 }
 
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ ld/testsuite/ld-elf/linkoncerdiff.d	22 Oct 2008 21:51:02 -0000
@@ -0,0 +1,5 @@
+#source: linkoncerdiff1.s
+#source: linkoncerdiff2.s
+#ld: -r
+#objdump: -r
+#pass
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ ld/testsuite/ld-elf/linkoncerdiff1.s	22 Oct 2008 21:51:02 -0000
@@ -0,0 +1,3 @@
+	.section	.gnu.linkonce.t.foo, "a", %progbits
+1:
+sym:
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ ld/testsuite/ld-elf/linkoncerdiff2.s	22 Oct 2008 21:51:02 -0000
@@ -0,0 +1,8 @@
+	.section	.gnu.linkonce.t.foo, "a", %progbits
+1:
+sym:
+	.long	0
+
+	.section	.gnu.linkonce.r.foo, "a", %progbits
+	.long	1b
+	.long	sym