PR ld/20276: Set non_ir_ref on common symbol

Also, don't check alignment on symbol from plugin dummy input.

bfd/
	PR ld/20276
	* elflink.c (elf_link_add_object_symbols): Don't check alignment
	on symbol from plugin dummy input.
ld/
	PR ld/20276
	* plugin.c (plugin_notice): Set non_ir_ref on common symbols.
	* testsuite/ld-plugin/lto.exp (lto_link_tests): Add test for
	PR ld/20276.
	(lto_run_tests): Likewise.
	* testsuite/ld-plugin/pass.out: New file.
	* testsuite/ld-plugin/pr20276a.c: Likewise.
	* testsuite/ld-plugin/pr20276b.c: Likewise.

6 files changed, 58 insertions, 13 deletions

diff --git a/ld/ChangeLog b/ld/ChangeLog
index b9b9c3e..cd161ab 100644
--- a/ld/ChangeLog
+++ b/ld/ChangeLog
@@ -1,3 +1,15 @@
+2016-06-20  H.J. Lu  <hongjiu.lu@intel.com>
+	    Alan Modra  <amodra@gmail.com>
+
+	PR ld/20276
+	* plugin.c (plugin_notice): Set non_ir_ref on common symbols.
+	* testsuite/ld-plugin/lto.exp (lto_link_tests): Add test for
+	PR ld/20276.
+	(lto_run_tests): Likewise.
+	* testsuite/ld-plugin/pass.out: New file.
+	* testsuite/ld-plugin/pr20276a.c: Likewise.
+	* testsuite/ld-plugin/pr20276b.c: Likewise.
+
 2016-06-18  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* plugin.c (plugin_object_p): Replace bfd_plugin_uknown
diff --git a/ld/plugin.c b/ld/plugin.c
index cb61318..4c161d1 100644
--- a/ld/plugin.c
+++ b/ld/plugin.c
@@ -1325,20 +1325,30 @@ plugin_notice (struct bfd_link_info *info,
 	  h->non_ir_ref = TRUE;
 	}
 
-      /* Otherwise, it must be a new def.  Ensure any symbol defined
-	 in an IR dummy BFD takes on a new value from a real BFD.
-	 Weak symbols are not normally overridden by a new weak
-	 definition, and strong symbols will normally cause multiple
-	 definition errors.  Avoid this by making the symbol appear
-	 to be undefined.  */
-      else if (((h->type == bfd_link_hash_defweak
-		 || h->type == bfd_link_hash_defined)
-		&& is_ir_dummy_bfd (sym_bfd = h->u.def.section->owner))
-	       || (h->type == bfd_link_hash_common
-		   && is_ir_dummy_bfd (sym_bfd = h->u.c.p->section->owner)))
+      /* Otherwise, it must be a new def.  */
+      else
 	{
-	  h->type = bfd_link_hash_undefweak;
-	  h->u.undef.abfd = sym_bfd;
+	  /* A common symbol should be merged with other commons or
+	     defs with the same name.  In particular, a common ought
+	     to be overridden by a def in a -flto object.  In that
+	     sense a common is also a ref.  */
+	  if (bfd_is_com_section (section))
+	    h->non_ir_ref = TRUE;
+
+	  /* Ensure any symbol defined in an IR dummy BFD takes on a
+	     new value from a real BFD.  Weak symbols are not normally
+	     overridden by a new weak definition, and strong symbols
+	     will normally cause multiple definition errors.  Avoid
+	     this by making the symbol appear to be undefined.  */
+	  if (((h->type == bfd_link_hash_defweak
+		|| h->type == bfd_link_hash_defined)
+	       && is_ir_dummy_bfd (sym_bfd = h->u.def.section->owner))
+	      || (h->type == bfd_link_hash_common
+		  && is_ir_dummy_bfd (sym_bfd = h->u.c.p->section->owner)))
+	    {
+	      h->type = bfd_link_hash_undefweak;
+	      h->u.undef.abfd = sym_bfd;
+	    }
 	}
     }
 
diff --git a/ld/testsuite/ld-plugin/lto.exp b/ld/testsuite/ld-plugin/lto.exp
index 7a13abb..7743719 100644
--- a/ld/testsuite/ld-plugin/lto.exp
+++ b/ld/testsuite/ld-plugin/lto.exp
@@ -183,6 +183,12 @@ set lto_link_tests [list \
   [list "PR ld/19317 (1)" \
    "$plug_opt" "-flto $lto_no_fat" \
    {pr19317.c} {} "libpr19317.a"] \
+  [list "Build pr20276a.o" \
+   "" "-fno-lto" \
+   {pr20276a.c}] \
+  [list "Build pr20276b.o" \
+   "$plug_opt" "-flto $lto_no_fat" \
+   {pr20276b.c}] \
 ]
 
 if { [at_least_gcc_version 4 7] } {
@@ -332,6 +338,9 @@ set lto_run_tests [list \
   [list "PR ld/19317 (3)" \
    "-O2 -flto tmpdir/pr19317-r.o" "" \
    {dummy.c} "pr19317.exe" "pr19317.out" "-flto -O2" "c"] \
+  [list "Run pr20276" \
+   "-O2 -flto tmpdir/pr20276a.o tmpdir/pr20276b.o" "" \
+   {dummy.c} "pr20276" "pass.out" "-flto -O2" "c"] \
 ]
 
 if { [at_least_gcc_version 4 7] } {
diff --git a/ld/testsuite/ld-plugin/pass.out b/ld/testsuite/ld-plugin/pass.out
new file mode 100644
index 0000000..7ef22e9
--- /dev/null
+++ b/ld/testsuite/ld-plugin/pass.out
@@ -0,0 +1 @@
+PASS
diff --git a/ld/testsuite/ld-plugin/pr20276a.c b/ld/testsuite/ld-plugin/pr20276a.c
new file mode 100644
index 0000000..0b37bc7
--- /dev/null
+++ b/ld/testsuite/ld-plugin/pr20276a.c
@@ -0,0 +1,12 @@
+#include <stdio.h>
+
+int global_var;
+extern void abort ();
+
+int main(void)
+{
+  if (global_var != 20)
+    abort ();
+  printf ("PASS\n");
+  return 0;
+}
diff --git a/ld/testsuite/ld-plugin/pr20276b.c b/ld/testsuite/ld-plugin/pr20276b.c
new file mode 100644
index 0000000..2ecbc2c
--- /dev/null
+++ b/ld/testsuite/ld-plugin/pr20276b.c
@@ -0,0 +1 @@
+int global_var = 20;