Handle symbol defined in IR and referenced in DSO

We need to make an IR symbol visible if it is defined in an IR object
and referenced in a dynamic object.  When --as-needed is used, since
linker removes the IR symbol reference of the dynamic object if the
dynamic object isn't needed in the first pass, the IR definition isn't
visible to the dynamic object even if the dynamic object becomes needed
in the second pass.  Add dynamic_ref_after_ir_def to bfd_link_hash_entry
to track IR symbol which is defined in an IR object and later referenced
in a dynamic object.  dynamic_ref_after_ir_def is preserved when restoring
the symbol table for unneeded dynamic object.

bfd/

	PR ld/21382
	* elflink.c (elf_link_add_object_symbols): Preserve
	dynamic_ref_after_ir_def when restoring the symbol table for
	unneeded dynamic object.

include/

	PR ld/21382
	* bfdlink.h (bfd_link_hash_entry): Add dynamic_ref_after_ir_def.

ld/

	PR ld/21382
	* plugin.c (is_visible_from_outside): Symbol may be visible
	from outside if dynamic_ref_after_ir_def is set.
	(plugin_notice): Set dynamic_ref_after_ir_def if the symbol is
	defined in an IR object and referenced in a dynamic object.
	* testsuite/ld-plugin/lto.exp: Run PR ld/21382 tests.
	* testsuite/ld-plugin/pr21382a.c: New file.
	* testsuite/ld-plugin/pr21382b.c: Likewise.

5 files changed, 61 insertions, 6 deletions

diff --git a/ld/ChangeLog b/ld/ChangeLog
index bccd2be..208c119 100644
--- a/ld/ChangeLog
+++ b/ld/ChangeLog
@@ -1,3 +1,14 @@
+2017-04-20  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR ld/21382
+	* plugin.c (is_visible_from_outside): Symbol may be visible
+	from outside if dynamic_ref_after_ir_def is set.
+	(plugin_notice): Set dynamic_ref_after_ir_def if the symbol is
+	defined in an IR object and referenced in a dynamic object.
+	* testsuite/ld-plugin/lto.exp: Run PR ld/21382 tests.
+	* testsuite/ld-plugin/pr21382a.c: New file.
+	* testsuite/ld-plugin/pr21382b.c: Likewise.
+
 2017-04-19  H.J. Lu  <hongjiu.lu@intel.com>
 
 	PR ld/21401
diff --git a/ld/plugin.c b/ld/plugin.c
index 03e2e69..164b5db 100644
--- a/ld/plugin.c
+++ b/ld/plugin.c
@@ -629,7 +629,9 @@ is_visible_from_outside (struct ld_plugin_symbol *lsym,
 
   if (bfd_link_relocatable (&link_info))
     return TRUE;
-  if (link_info.export_dynamic || bfd_link_dll (&link_info))
+  if (blhe->dynamic_ref_after_ir_def
+      || link_info.export_dynamic
+      || bfd_link_dll (&link_info))
     {
       /* Check if symbol is hidden by version script.  */
       if (bfd_hide_sym_by_version (link_info.version_info,
@@ -1316,12 +1318,21 @@ plugin_notice (struct bfd_link_info *info,
       /* If this is a ref, set non_ir_ref.  */
       else if (bfd_is_und_section (section))
 	{
+	   if (h->type == bfd_link_hash_defweak
+	       || h->type == bfd_link_hash_defined)
+	     {
+	       /* Check if the symbol is referenced in a dynamic object
+		  after it has been defined in an IR object.  */
+	       if ((abfd->flags & DYNAMIC) != 0
+		   && is_ir_dummy_bfd (h->u.def.section->owner))
+		 h->dynamic_ref_after_ir_def = TRUE;
+	     }
 	  /* Replace the undefined dummy bfd with the real one.  */
-	  if ((h->type == bfd_link_hash_undefined
-	       || h->type == bfd_link_hash_undefweak)
-	      && (h->u.undef.abfd == NULL
-		  || (h->u.undef.abfd->flags & BFD_PLUGIN) != 0))
-	    h->u.undef.abfd = abfd;
+	   else if ((h->type == bfd_link_hash_undefined
+		     || h->type == bfd_link_hash_undefweak)
+		    && (h->u.undef.abfd == NULL
+			|| (h->u.undef.abfd->flags & BFD_PLUGIN) != 0))
+	     h->u.undef.abfd = abfd;
 	  h->non_ir_ref = TRUE;
 	}
 
diff --git a/ld/testsuite/ld-plugin/lto.exp b/ld/testsuite/ld-plugin/lto.exp
index 80c084b..f0bc345 100644
--- a/ld/testsuite/ld-plugin/lto.exp
+++ b/ld/testsuite/ld-plugin/lto.exp
@@ -289,6 +289,12 @@ set lto_link_elf_tests [list \
   [list "PR ld/14918" \
    "-flto" "-flto" \
    {pr14918.c} {{"readelf" {-d --wide} "pr14918.d"}} "pr14918.exe" "c"] \
+  [list "Build pr21382a.o" \
+   "" "-O2 -flto" \
+   {pr21382a.c} {} "" "c"] \
+  [list "Build pr21382.so" \
+   "-shared" "-O2 -fpic" \
+   {pr21382b.c} {} "pr21382.so" "c"] \
 ]
 
 # Check final symbols in executables.
@@ -387,6 +393,9 @@ set lto_run_elf_shared_tests [list \
   [list "LTO 7" \
    "-O2 -flto -fuse-linker-plugin tmpdir/lto-7b.o tmpdir/lto-7c.o tmpdir/lto-7a.o -Wl,--no-as-needed tmpdir/liblto-7.so" "" \
    {dummy.c} "lto-7.exe" "lto-7.out" "" "c"] \
+  [list "Run pr21382" \
+   "-O2 -flto -fuse-linker-plugin -Wl,--as-needed tmpdir/pr21382a.o tmpdir/pr21382.so" "" \
+   {dummy.c} "pr21382.exe" "pass.out" "" "c"] \
 ]
 
 # LTO run-time tests for ELF
diff --git a/ld/testsuite/ld-plugin/pr21382a.c b/ld/testsuite/ld-plugin/pr21382a.c
new file mode 100644
index 0000000..09b9d75
--- /dev/null
+++ b/ld/testsuite/ld-plugin/pr21382a.c
@@ -0,0 +1,17 @@
+#include <stdio.h>
+
+extern void y (void);
+
+void
+x (void)
+{
+  printf ("PASS\n");
+}
+
+
+int
+main (void)
+{
+  y ();
+  return 0;
+}
diff --git a/ld/testsuite/ld-plugin/pr21382b.c b/ld/testsuite/ld-plugin/pr21382b.c
new file mode 100644
index 0000000..c5b74a9
--- /dev/null
+++ b/ld/testsuite/ld-plugin/pr21382b.c
@@ -0,0 +1,7 @@
+extern void x (void);
+
+void
+y (void)
+{
+  x ();
+}