re PR c++/42608 (Undefined reference not reported in case of explicit template instantiation)

	PR c++/42608
	* varasm.c (declare_weak): Add weak attribute to decl if it
	doesn't have one already.
	(assemble_external): Only add decls to weak_decls if they also
	have weak attribute.

	* g++.dg/template/instantiate11.C: New test.

From-SVN: r155919

gcc/ChangeLog

+2010-01-14  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/42608
+	* varasm.c (declare_weak): Add weak attribute to decl if it
+	doesn't have one already.
+	(assemble_external): Only add decls to weak_decls if they also
+	have weak attribute.
+
 2010-01-14  Alexandre Oliva  <aoliva@redhat.com>
 
 	* var-tracking.c (var_reg_delete): Don't delete the association

gcc/testsuite/ChangeLog

+2010-01-14  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/42608
+	* g++.dg/template/instantiate11.C: New test.
+
 2010-01-14  Jason Merrill  <jason@redhat.com>
 
 	PR c++/42701

gcc/testsuite/g++.dg/template/instantiate11.C

+// PR c++/42608
+// { dg-do compile }
+
+template <class U, class V>
+struct A;
+
+template <class V>
+struct A<int, V>
+{
+  void f ();
+};
+
+template struct A<int, int>;
+
+int
+main ()
+{
+  A<int, int> a;
+  a.f ();
+  return 0;
+}
+
+// Make sure we get undefined reference error if
+// A<int, int>::f () isn't instantiated elsewhere.
+// { dg-final { scan-assembler-not "weak\[\n\t\]*_ZN1AIiiE1fEv" } }

gcc/varasm.c

@@ -2337,13 +2337,15 @@ assemble_external (tree decl ATTRIBUTE_UNUSED)
   /* We want to output annotation for weak and external symbols at
      very last to check if they are references or not.  */
 
-  if (SUPPORTS_WEAK && DECL_WEAK (decl)
+  if (SUPPORTS_WEAK
+      && DECL_WEAK (decl)
       /* TREE_STATIC is a weird and abused creature which is not
 	 generally the right test for whether an entity has been
 	 locally emitted, inlined or otherwise not-really-extern, but
 	 for declarations that can be weak, it happens to be
 	 match.  */
       && !TREE_STATIC (decl)
+      && lookup_attribute ("weak", DECL_ATTRIBUTES (decl))
       && value_member (decl, weak_decls) == NULL_TREE)
     weak_decls = tree_cons (NULL, decl, weak_decls);
 
@@ -5227,6 +5229,9 @@ declare_weak (tree decl)
     warning (0, "weak declaration of %q+D not supported", decl);
 
   mark_weak (decl);
+  if (!lookup_attribute ("weak", DECL_ATTRIBUTES (decl)))
+    DECL_ATTRIBUTES (decl)
+      = tree_cons (get_identifier ("weak"), NULL, DECL_ATTRIBUTES (decl));
 }
 
 static void