* name-lookup.c (parse_using_directive): Deprecate strong using.

From-SVN: r244936

gcc/cp/ChangeLog

 2017-01-26  Jason Merrill  <jason@redhat.com>
 
+	* name-lookup.c (parse_using_directive): Deprecate strong using.
+
 	PR c++/79176 - lambda ICE with -flto -Os
 	* decl2.c (vague_linkage_p): Handle decloned 'tors.
 	* tree.c (decl_linkage): Likewise.

gcc/cp/name-lookup.c

@@ -4125,6 +4125,8 @@ parse_using_directive (tree name_space, tree attribs)
       tree name = get_attribute_name (a);
       if (is_attribute_p ("strong", name))
 	{
+	  warning (OPT_Wdeprecated, "strong using is deprecated; use inline "
+		   "namespaces instead");
 	  if (!toplevel_bindings_p ())
 	    error ("strong using only meaningful at namespace scope");
 	  else if (name_space != error_mark_node)

gcc/doc/extend.texi

@@ -21802,7 +21802,6 @@ Predefined Macros,cpp,The GNU C Preprocessor}).
                         method denoted by a @samp{->*} or @samp{.*} expression.
 * C++ Attributes::      Variable, function, and type attributes for C++ only.
 * Function Multiversioning::   Declaring multiple function versions.
-* Namespace Association:: Strong using-directives for namespace association.
 * Type Traits::         Compiler support for type traits.
 * C++ Concepts::        Improved support for generic programming.
 * Deprecated Features:: Things will disappear from G++.
@@ -22368,8 +22367,6 @@ does not have constructors or destructors.
 
 @end table
 
-See also @ref{Namespace Association}.
-
 @node Function Multiversioning
 @section Function Multiversioning
 @cindex function versions
@@ -22428,51 +22425,6 @@ dispatching to call the right version at runtime.  Refer to the
 @uref{http://gcc.gnu.org/wiki/FunctionMultiVersioning, GCC wiki on
 Function Multiversioning} for more details.
 
-@node Namespace Association
-@section Namespace Association
-
-@strong{Caution:} The semantics of this extension are equivalent
-to C++ 2011 inline namespaces.  Users should use inline namespaces
-instead as this extension will be removed in future versions of G++.
-
-A using-directive with @code{__attribute ((strong))} is stronger
-than a normal using-directive in two ways:
-
-@itemize @bullet
-@item
-Templates from the used namespace can be specialized and explicitly
-instantiated as though they were members of the using namespace.
-
-@item
-The using namespace is considered an associated namespace of all
-templates in the used namespace for purposes of argument-dependent
-name lookup.
-@end itemize
-
-The used namespace must be nested within the using namespace so that
-normal unqualified lookup works properly.
-
-This is useful for composing a namespace transparently from
-implementation namespaces.  For example:
-
-@smallexample
-namespace std @{
-  namespace debug @{
-    template <class T> struct A @{ @};
-  @}
-  using namespace debug __attribute ((__strong__));
-  template <> struct A<int> @{ @};   // @r{OK to specialize}
-
-  template <class T> void f (A<T>);
-@}
-
-int main()
-@{
-  f (std::A<float>());             // @r{lookup finds} std::f
-  f (std::A<int>());
-@}
-@end smallexample
-
 @node Type Traits
 @section Type Traits
 

gcc/testsuite/g++.dg/lookup/strong-using-4.C

-// PR c++/16301
-
-// { dg-do compile }
-
-namespace NS2 
-{ 
-  using namespace NS1 __attribute__ ((strong));  // { dg-error "" }
-}

libstdc++-v3/doc/html/manual/debug_mode_design.html

@@ -250,7 +250,6 @@ namespace std
       };
   } // namespace __cxx1998
 
-  // namespace __debug __attribute__ ((strong));
   inline namespace __debug { }
 }
 </pre></div><div class="section"><div class="titlepage"><div><div><h5 class="title"><a id="methods.coexistence.link"></a>Link- and run-time coexistence of release- and

libstdc++-v3/doc/xml/manual/debug_mode.xml

@@ -656,7 +656,6 @@ namespace std
       };
   } // namespace __cxx1998
 
-  // namespace __debug __attribute__ ((strong));
   inline namespace __debug { }
 }
 </programlisting>