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C++ PATCH to warn about "strong using"

Message ID CADzB+2=i1RyeT8uYgZQRHjq5xWHQ9m3jrupY35LMPy0fegQsow@mail.gmail.com
State New
Headers show

Commit Message

Jason Merrill Jan. 26, 2017, 3:29 p.m. UTC
Attribute "strong" on a using-directive was a G++ extension that
eventually became C++11 inline namespaces.  It's been documented as
deprecated for a while, but we didn't actually warn about it.  This
patch adds such a warning and removes the documentation.

Tested x86_64-pc-linux-gnu, applying to trunk.
commit 60ef52152fb50569e5f8ac08c149254bc44aa02c
Author: Jason Merrill <jason@redhat.com>
Date:   Tue Jan 24 14:31:24 2017 -0500

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

diff --git a/gcc/cp/name-lookup.c b/gcc/cp/name-lookup.c
index 4004640..10fb540 100644
--- a/gcc/cp/name-lookup.c
+++ b/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)
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index 5cb4748..20eba82 100644
--- a/gcc/doc/extend.texi
+++ b/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
 
diff --git a/gcc/testsuite/g++.dg/lookup/strong-using-1.C b/gcc/testsuite/g++.dg/cpp0x/inline-ns6.C
similarity index 100%
rename from gcc/testsuite/g++.dg/lookup/strong-using-1.C
rename to gcc/testsuite/g++.dg/cpp0x/inline-ns6.C
diff --git a/gcc/testsuite/g++.dg/lookup/strong-using-2.C b/gcc/testsuite/g++.dg/cpp0x/inline-ns7.C
diff --git a/gcc/testsuite/g++.dg/lookup/strong-using-2.C b/gcc/testsuite/g++.dg/cpp0x/inline-ns7.C
similarity index 100%
rename from gcc/testsuite/g++.dg/lookup/strong-using-2.C
rename to gcc/testsuite/g++.dg/cpp0x/inline-ns7.C
diff --git a/gcc/testsuite/g++.dg/lookup/strong-using-3.C b/gcc/testsuite/g++.dg/cpp0x/inline-ns8.C
diff --git a/gcc/testsuite/g++.dg/lookup/strong-using-3.C b/gcc/testsuite/g++.dg/cpp0x/inline-ns8.C
similarity index 100%
rename from gcc/testsuite/g++.dg/lookup/strong-using-3.C
rename to gcc/testsuite/g++.dg/cpp0x/inline-ns8.C
diff --git a/gcc/testsuite/g++.dg/lookup/strong-using-5.C b/gcc/testsuite/g++.dg/cpp0x/inline-ns9.C
diff --git a/gcc/testsuite/g++.dg/lookup/strong-using-5.C b/gcc/testsuite/g++.dg/cpp0x/inline-ns9.C
similarity index 100%
rename from gcc/testsuite/g++.dg/lookup/strong-using-5.C
rename to gcc/testsuite/g++.dg/cpp0x/inline-ns9.C
diff --git a/gcc/testsuite/g++.dg/lookup/strong-using-4.C b/gcc/testsuite/g++.dg/lookup/strong-using-4.C
diff --git a/gcc/testsuite/g++.dg/lookup/strong-using-4.C b/gcc/testsuite/g++.dg/lookup/strong-using-4.C
deleted file mode 100644
index 5ea1784..0000000
--- a/gcc/testsuite/g++.dg/lookup/strong-using-4.C
+++ /dev/null
@@ -1,8 +0,0 @@ 
-// PR c++/16301
-
-// { dg-do compile }
-
-namespace NS2 
-{ 
-  using namespace NS1 __attribute__ ((strong));  // { dg-error "" }
-}
diff --git a/libstdc++-v3/doc/html/manual/debug_mode_design.html b/libstdc++-v3/doc/html/manual/debug_mode_design.html
index 3373471..3fcdb2d 100644
--- a/libstdc++-v3/doc/html/manual/debug_mode_design.html
+++ b/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
diff --git a/libstdc++-v3/doc/xml/manual/debug_mode.xml b/libstdc++-v3/doc/xml/manual/debug_mode.xml
index ff2f1cc..9e97a1d 100644
--- a/libstdc++-v3/doc/xml/manual/debug_mode.xml
+++ b/libstdc++-v3/doc/xml/manual/debug_mode.xml
@@ -656,7 +656,6 @@  namespace std
       };
   } // namespace __cxx1998
 
-  // namespace __debug __attribute__ ((strong));
   inline namespace __debug { }
 }
 </programlisting>