Don't complain undefined weak dynamic reference

When undefined non-weak references in IR objects are optimized out
by LTO, we can have weak dynamic referencs to symbols marked with
bfd_link_hash_undefined.  We shouldn't complain such undefined weak
dynamic references.

bfd/

	PR ld/24486
	* elflink.c (elf_link_output_extsym): Don't complain undefined
	weak dynamic reference.

ld/

	PR ld/24486
	* testsuite/ld-plugin/lto.exp: Run PR ld/24486 tests.
	* testsuite/ld-plugin/pr24486a.c: New file.
	* testsuite/ld-plugin/pr24486b.c: Likewise.
	* testsuite/ld-plugin/pr24486c.c: Likewise.

bfd/ChangeLog

@@ -1,3 +1,9 @@
+2019-04-26  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR ld/24486
+	* elflink.c (elf_link_output_extsym): Don't complain undefined
+	weak dynamic reference.
+
 2019-04-25  Sudakshina Das  <sudi.das@arm.com>
 
 	* elfnn-aarch64.c (PLT_BTI_ENTRY_SIZE): Remove.

bfd/elflink.c

@@ -9776,7 +9776,7 @@ elf_link_output_extsym (struct bfd_hash_entry *bh, void *data)
 
       /* If we are reporting errors for this situation then do so now.  */
       if (!ignore_undef
-	  && h->ref_dynamic
+	  && h->ref_dynamic_nonweak
 	  && (!h->ref_regular || flinfo->info->gc_sections)
 	  && !elf_link_check_versioned_symbol (flinfo->info, bed, h)
 	  && flinfo->info->unresolved_syms_in_shared_libs != RM_IGNORE)

ld/ChangeLog

@@ -1,3 +1,11 @@
+2019-04-26  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR ld/24486
+	* testsuite/ld-plugin/lto.exp: Run PR ld/24486 tests.
+	* testsuite/ld-plugin/pr24486a.c: New file.
+	* testsuite/ld-plugin/pr24486b.c: Likewise.
+	* testsuite/ld-plugin/pr24486c.c: Likewise.
+
 2019-04-26  Nick Clifton  <nickc@redhat.com>
 
 	* po/ru.po: Updated Russian translation.

ld/testsuite/ld-plugin/lto.exp

@@ -325,6 +325,18 @@ set lto_link_elf_tests [list \
   [list {Build pr22220main.o} \
    {} {-flto} \
    {pr22220main.cc} {} {} {c++}] \
+  [list "Build pr24486a.o" \
+   "$plug_opt" "-flto -O2" \
+   {pr24486a.c} {} "" "c"] \
+  [list "Build pr24486b.so" \
+   "-shared" "-O2 -fpic" \
+   {pr24486b.c} {} "pr24486b.so" "c"] \
+  [list "Build pr24486c.so" \
+   "-shared -Wl,--no-as-needed tmpdir/pr24486b.so" "-O2 -fpic" \
+   {pr24486c.c} {} "pr24486c.so" "c"] \
+  [list "PR ld/24486" \
+   "-O2 -flto tmpdir/pr24486a.o tmpdir/pr24486c.so -Wl,--as-needed tmpdir/pr24486b.so" "" \
+   {dummy.c} {} "pr24486.exe"] \
 ]
 
 # PR 14918 checks that libgcc is not spuriously included in a shared link of

ld/testsuite/ld-plugin/pr24486a.c

@@ -0,0 +1,8 @@
+extern int FLAGS_verbose;
+extern void bar (void);
+int
+a(void) {
+return FLAGS_verbose;
+}
+void unused (void) { bar(); }
+int main() { return a (); }

ld/testsuite/ld-plugin/pr24486b.c

@@ -0,0 +1,8 @@
+extern void bar (void) __attribute__((weak));
+
+void
+foo (void)
+{
+  if (bar)
+    bar ();
+}

ld/testsuite/ld-plugin/pr24486c.c

@@ -0,0 +1 @@
+int FLAGS_verbose;