diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 76d86fbf705..a52fc961619 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,40 @@
+2017-01-13  Jonathan Wakely  <jwakely@redhat.com>
+
+	PR libstdc++/79075
+	* testsuite/lib/libstdc++.exp (check_v3_target_filesystem_ts): Remove
+	redundant option from cxxflags.
+	(check_effective_target_cxx11-abi): Define.
+	* testsuite/21_strings/basic_string/allocator/71964.cc: Use cxx11-abi
+	effective target.
+	* testsuite/21_strings/basic_string/allocator/char/copy.cc: Likewise.
+	* testsuite/21_strings/basic_string/allocator/char/copy_assign.cc:
+	Likewise.
+	* testsuite/21_strings/basic_string/allocator/char/minimal.cc:
+	Likewise.
+	* testsuite/21_strings/basic_string/allocator/char/move.cc: Likewise.
+	* testsuite/21_strings/basic_string/allocator/char/move_assign.cc:
+	Likewise.
+	* testsuite/21_strings/basic_string/allocator/char/noexcept.cc:
+	Likewise.
+	* testsuite/21_strings/basic_string/allocator/char/swap.cc: Likewise.
+	* testsuite/21_strings/basic_string/allocator/wchar_t/copy.cc:
+	Likewise.
+	* testsuite/21_strings/basic_string/allocator/wchar_t/copy_assign.cc:
+	Likewise.
+	* testsuite/21_strings/basic_string/allocator/wchar_t/minimal.cc:
+	Likewise.
+	* testsuite/21_strings/basic_string/allocator/wchar_t/move.cc:
+	Likewise.
+	* testsuite/21_strings/basic_string/allocator/wchar_t/move_assign.cc:
+	Likewise.
+	* testsuite/21_strings/basic_string/allocator/wchar_t/noexcept.cc:
+	Likewise.
+	* testsuite/21_strings/basic_string/allocator/wchar_t/swap.cc:
+	Likewise.
+	* testsuite/23_containers/list/61347.cc: Likewise.
+	* testsuite/27_io/basic_fstream/cons/base.cc: Likewise.
+	* testsuite/27_io/ios_base/failure/cxx11.cc: Likewise.
+
 2017-01-13  Ville Voutilainen  <ville.voutilainen@gmail.com>
 
 	PR libstdc++/78389
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/71964.cc b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/71964.cc
index f5ef176cdfd..70e5cf88dc9 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/71964.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/71964.cc
@@ -16,6 +16,8 @@
 // <http://www.gnu.org/licenses/>.
 
 // { dg-do run { target c++11 } }
+// COW strings don't support C++11 allocators:
+// { dg-require-effective-target cxx11-abi }
 
 #include <string>
 #include <testsuite_hooks.h>
@@ -58,13 +60,10 @@ operator!=(const mv_allocator<T>&, const mv_allocator<U>&) { return false; }
 void
 test01()
 {
-  // COW strings don't support C++11 allocators
-#if _GLIBCXX_USE_CXX11_ABI
   std::basic_string<char, std::char_traits<char>, mv_allocator<char>> s;
   auto t = std::move(s);
   VERIFY( s.get_allocator().moved_from );
   VERIFY( t.get_allocator().moved_to );
-#endif
 }
 
 int
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/copy.cc b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/copy.cc
index 0e5f167f153..bdcadaf1e02 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/copy.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/copy.cc
@@ -16,12 +16,13 @@
 // <http://www.gnu.org/licenses/>.
 
 // { dg-do run { target c++11 } }
+// COW strings don't support C++11 allocators:
+// { dg-require-effective-target cxx11-abi }
 
 #include <string>
 #include <testsuite_hooks.h>
 #include <testsuite_allocator.h>
  
-#if _GLIBCXX_USE_CXX11_ABI
 using C = char;
 const C c = 'a';
 using traits = std::char_traits<C>;
@@ -86,9 +87,3 @@ int main()
   test03();
   return 0;
 }
-#else
-int main()
-{
-  // COW strings don't support C++11 allocators
-}
-#endif
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/copy_assign.cc b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/copy_assign.cc
index 5b9a0b0507c..32ee708f3c6 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/copy_assign.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/copy_assign.cc
@@ -16,12 +16,13 @@
 // <http://www.gnu.org/licenses/>.
 
 // { dg-do run { target c++11 } }
+// COW strings don't support C++11 allocators:
+// { dg-require-effective-target cxx11-abi }
 
 #include <string>
 #include <testsuite_hooks.h>
 #include <testsuite_allocator.h>
  
-#if _GLIBCXX_USE_CXX11_ABI
 using C = char;
 const C c = 'a';
 using traits = std::char_traits<C>;
@@ -104,9 +105,3 @@ int main()
   test02();
   return 0;
 }
-#else
-int main()
-{
-  // COW strings don't support C++11 allocators
-}
-#endif
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/minimal.cc b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/minimal.cc
index 6f0aeb59335..46b4215bcf2 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/minimal.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/minimal.cc
@@ -16,13 +16,14 @@
 // <http://www.gnu.org/licenses/>.
 
 // { dg-do run { target c++11 } }
+// COW strings don't support C++11 allocators:
+// { dg-require-effective-target cxx11-abi }
 
 #include <string>
 #include <memory>
 #include <testsuite_hooks.h>
 #include <testsuite_allocator.h>
  
-#if _GLIBCXX_USE_CXX11_ABI
 using C = char;
 const C c = 'a';
 using traits = std::char_traits<C>;
@@ -40,9 +41,6 @@ void test01()
   v.assign(1, c);
   v.assign(100, c);
 }
-#else
-void test01() { }
-#endif
 
 int main()
 {
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/move.cc b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/move.cc
index 4e45a053c51..820b3ed4791 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/move.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/move.cc
@@ -16,12 +16,13 @@
 // <http://www.gnu.org/licenses/>.
 
 // { dg-do run { target c++11 } }
+// COW strings don't support C++11 allocators:
+// { dg-require-effective-target cxx11-abi }
 
 #include <string>
 #include <testsuite_hooks.h>
 #include <testsuite_allocator.h>
 
-#if _GLIBCXX_USE_CXX11_ABI
 using C = char;
 const C c = 'a';
 using traits = std::char_traits<C>;
@@ -56,9 +57,3 @@ int main()
   test02();
   return 0;
 }
-#else
-int main()
-{
-  // COW strings don't support C++11 allocators
-}
-#endif
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/move_assign.cc b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/move_assign.cc
index 0151a29d5f0..df85a0b2861 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/move_assign.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/move_assign.cc
@@ -16,12 +16,13 @@
 // <http://www.gnu.org/licenses/>.
 
 // { dg-do run { target c++11 } }
+// COW strings don't support C++11 allocators:
+// { dg-require-effective-target cxx11-abi }
 
 #include <string>
 #include <testsuite_hooks.h>
 #include <testsuite_allocator.h>
  
-#if _GLIBCXX_USE_CXX11_ABI
 using C = char;
 const C c = 'a';
 using traits = std::char_traits<C>;
@@ -149,9 +150,3 @@ int main()
   test03();
   return 0;
 }
-#else
-int main()
-{
-  // COW strings don't support C++11 allocators
-}
-#endif
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/noexcept.cc b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/noexcept.cc
index b7917e01143..90aca89a10c 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/noexcept.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/noexcept.cc
@@ -16,11 +16,12 @@
 // <http://www.gnu.org/licenses/>.
 
 // { dg-do compile { target c++11 } }
+// COW strings don't support C++11 allocators:
+// { dg-require-effective-target cxx11-abi }
 
 #include <string>
 #include <testsuite_allocator.h>
  
-#if _GLIBCXX_USE_CXX11_ABI
 using C = char;
 const C c = 'a';
 using traits = std::char_traits<C>;
@@ -57,4 +58,3 @@ void test03()
   static_assert( noexcept( v1 = std::move(v2) ), "Move assign cannot throw" );
   static_assert( noexcept( v1.swap(v2) ), "Swap cannot throw" );
 }
-#endif
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/swap.cc b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/swap.cc
index 602d856e283..a7d9bdf96c4 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/swap.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/swap.cc
@@ -16,12 +16,13 @@
 // <http://www.gnu.org/licenses/>.
 
 // { dg-do run { target c++11 } }
+// COW strings don't support C++11 allocators:
+// { dg-require-effective-target cxx11-abi }
 
 #include <string>
 #include <testsuite_hooks.h>
 #include <testsuite_allocator.h>
  
-#if _GLIBCXX_USE_CXX11_ABI
 using C = char;
 const C c = 'a';
 using traits = std::char_traits<C>;
@@ -79,9 +80,3 @@ int main()
   test02();
   return 0;
 }
-#else
-int main()
-{
-  // COW strings don't support C++11 allocators
-}
-#endif
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/copy.cc b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/copy.cc
index 747a2d07967..add276c4e71 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/copy.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/copy.cc
@@ -16,12 +16,13 @@
 // <http://www.gnu.org/licenses/>.
 
 // { dg-do run { target c++11 } }
+// COW strings don't support C++11 allocators:
+// { dg-require-effective-target cxx11-abi }
 
 #include <string>
 #include <testsuite_hooks.h>
 #include <testsuite_allocator.h>
  
-#if _GLIBCXX_USE_CXX11_ABI
 using C = wchar_t;
 const C c = L'a';
 using traits = std::char_traits<C>;
@@ -86,9 +87,3 @@ int main()
   test03();
   return 0;
 }
-#else
-int main()
-{
-  // COW strings don't support C++11 allocators
-}
-#endif
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/copy_assign.cc b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/copy_assign.cc
index 775755653c9..89593ba8faa 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/copy_assign.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/copy_assign.cc
@@ -16,12 +16,13 @@
 // <http://www.gnu.org/licenses/>.
 
 // { dg-do run { target c++11 } }
+// COW strings don't support C++11 allocators:
+// { dg-require-effective-target cxx11-abi }
 
 #include <string>
 #include <testsuite_hooks.h>
 #include <testsuite_allocator.h>
  
-#if _GLIBCXX_USE_CXX11_ABI
 using C = wchar_t;
 const C c = L'a';
 using traits = std::char_traits<C>;
@@ -104,9 +105,3 @@ int main()
   test02();
   return 0;
 }
-#else
-int main()
-{
-  // COW strings don't support C++11 allocators
-}
-#endif
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/minimal.cc b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/minimal.cc
index dab694eefe1..f8e98853c16 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/minimal.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/minimal.cc
@@ -16,13 +16,14 @@
 // <http://www.gnu.org/licenses/>.
 
 // { dg-do run { target c++11 } }
+// COW strings don't support C++11 allocators:
+// { dg-require-effective-target cxx11-abi }
 
 #include <string>
 #include <memory>
 #include <testsuite_hooks.h>
 #include <testsuite_allocator.h>
  
-#if _GLIBCXX_USE_CXX11_ABI
 using C = wchar_t;
 const C c = L'a';
 using traits = std::char_traits<C>;
@@ -40,9 +41,6 @@ void test01()
   v.assign(1, c);
   v.assign(100, c);
 }
-#else
-void test01() { }
-#endif
 
 int main()
 {
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/move.cc b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/move.cc
index 7aba4405657..8db947fd8ff 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/move.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/move.cc
@@ -16,12 +16,13 @@
 // <http://www.gnu.org/licenses/>.
 
 // { dg-do run { target c++11 } }
+// COW strings don't support C++11 allocators:
+// { dg-require-effective-target cxx11-abi }
 
 #include <string>
 #include <testsuite_hooks.h>
 #include <testsuite_allocator.h>
 
-#if _GLIBCXX_USE_CXX11_ABI
 using C = wchar_t;
 const C c = L'a';
 using traits = std::char_traits<C>;
@@ -56,9 +57,3 @@ int main()
   test02();
   return 0;
 }
-#else
-int main()
-{
-  // COW strings don't support C++11 allocators
-}
-#endif
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/move_assign.cc b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/move_assign.cc
index 55b8c2a821c..9d282fcec94 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/move_assign.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/move_assign.cc
@@ -16,12 +16,13 @@
 // <http://www.gnu.org/licenses/>.
 
 // { dg-do run { target c++11 } }
+// COW strings don't support C++11 allocators:
+// { dg-require-effective-target cxx11-abi }
 
 #include <string>
 #include <testsuite_hooks.h>
 #include <testsuite_allocator.h>
  
-#if _GLIBCXX_USE_CXX11_ABI
 using C = wchar_t;
 const C c = L'a';
 using traits = std::char_traits<C>;
@@ -149,9 +150,3 @@ int main()
   test03();
   return 0;
 }
-#else
-int main()
-{
-  // COW strings don't support C++11 allocators
-}
-#endif
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/noexcept.cc b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/noexcept.cc
index 27548282fc4..c107737ee70 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/noexcept.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/noexcept.cc
@@ -16,11 +16,12 @@
 // <http://www.gnu.org/licenses/>.
 
 // { dg-do compile { target c++11 } }
+// COW strings don't support C++11 allocators:
+// { dg-require-effective-target cxx11-abi }
 
 #include <string>
 #include <testsuite_allocator.h>
  
-#if _GLIBCXX_USE_CXX11_ABI
 using C = wchar_t;
 const C c = L'a';
 using traits = std::char_traits<C>;
@@ -57,4 +58,3 @@ void test03()
   static_assert( noexcept( v1 = std::move(v2) ), "Move assign cannot throw" );
   static_assert( noexcept( v1.swap(v2) ), "Swap cannot throw" );
 }
-#endif
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/swap.cc b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/swap.cc
index bb1dd8252b7..842fb55d6e6 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/swap.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/swap.cc
@@ -16,12 +16,13 @@
 // <http://www.gnu.org/licenses/>.
 
 // { dg-do run { target c++11 } }
+// COW strings don't support C++11 allocators:
+// { dg-require-effective-target cxx11-abi }
 
 #include <string>
 #include <testsuite_hooks.h>
 #include <testsuite_allocator.h>
  
-#if _GLIBCXX_USE_CXX11_ABI
 using C = wchar_t;
 const C c = L'a';
 using traits = std::char_traits<C>;
@@ -79,9 +80,3 @@ int main()
   test02();
   return 0;
 }
-#else
-int main()
-{
-  // COW strings don't support C++11 allocators
-}
-#endif
diff --git a/libstdc++-v3/testsuite/23_containers/list/61347.cc b/libstdc++-v3/testsuite/23_containers/list/61347.cc
index bf5a20da45c..526ab329fa5 100644
--- a/libstdc++-v3/testsuite/23_containers/list/61347.cc
+++ b/libstdc++-v3/testsuite/23_containers/list/61347.cc
@@ -1,6 +1,7 @@
-// { dg-options "-O2 -D_GLIBCXX_USE_CXX11_ABI" }
+// { dg-options "-O2" }
 // { dg-do run { target c++11 } }
 // { dg-require-normal-mode "" }
+// { dg-require-effective-target cxx11-abi }
 
 // Copyright (C) 2015-2017 Free Software Foundation, Inc.
 //
diff --git a/libstdc++-v3/testsuite/27_io/basic_fstream/cons/base.cc b/libstdc++-v3/testsuite/27_io/basic_fstream/cons/base.cc
index 21fa2e64177..3b9436dedf0 100644
--- a/libstdc++-v3/testsuite/27_io/basic_fstream/cons/base.cc
+++ b/libstdc++-v3/testsuite/27_io/basic_fstream/cons/base.cc
@@ -15,8 +15,9 @@
 // with this library; see the file COPYING3.  If not see
 // <http://www.gnu.org/licenses/>.
 
-// { dg-options "-O0 -D_GLIBCXX_USE_CXX11_ABI=1" }
+// { dg-options "-O0" }
 // { dg-do link { target c++11 } }
+// { dg-require-effective-target cxx11-abi }
 
 #include <fstream>
 #include <string>
diff --git a/libstdc++-v3/testsuite/27_io/ios_base/failure/cxx11.cc b/libstdc++-v3/testsuite/27_io/ios_base/failure/cxx11.cc
index 99ad9292381..46b68b1c961 100644
--- a/libstdc++-v3/testsuite/27_io/ios_base/failure/cxx11.cc
+++ b/libstdc++-v3/testsuite/27_io/ios_base/failure/cxx11.cc
@@ -16,11 +16,11 @@
 // <http://www.gnu.org/licenses/>.
 
 // { dg-do run { target c++11 } }
+// { dg-require-effective-target cxx11-abi }
 
 #include <ios>
 #include <testsuite_hooks.h>
 
-#if _GLIBCXX_USE_CXX11_ABI
 using test_type = std::ios_base::failure;
 
 static_assert( std::is_base_of<std::system_error, test_type>::value, "base" );
@@ -51,6 +51,3 @@ main()
   test01();
   test02();
 }
-#else
-int main() { }
-#endif
diff --git a/libstdc++-v3/testsuite/lib/libstdc++.exp b/libstdc++-v3/testsuite/lib/libstdc++.exp
index 9f0e26b8725..b081d8a5b90 100644
--- a/libstdc++-v3/testsuite/lib/libstdc++.exp
+++ b/libstdc++-v3/testsuite/lib/libstdc++.exp
@@ -1968,7 +1968,7 @@ proc check_v3_target_filesystem_ts { } {
 	close $f
 
 	set cxxflags_saved $cxxflags
-	set cxxflags "$cxxflags $DEFAULT_CXXFLAGS -Werror -std=gnu++11"
+	set cxxflags "$cxxflags $DEFAULT_CXXFLAGS -Werror"
 
 	set lines [v3_target_compile $src /dev/null preprocess ""]
 	set cxxflags $cxxflags_saved
@@ -1983,6 +1983,34 @@ proc check_v3_target_filesystem_ts { } {
     return $et_filesystem_ts
 }
 
+# Return 1 if the "cxx11" ABI is in use using the current flags, 0 otherwise.
+proc check_effective_target_cxx11-abi { } {
+    global cxxflags
+
+    # Set up and preprocess a C++ test program that depends
+    # on the new ABI being enabled.
+    set src cxx11_abi[pid].cc
+
+    set f [open $src "w"]
+    puts $f "#include <bits/c++config.h>"
+    puts $f "#if ! _GLIBCXX_USE_CXX11_ABI"
+    puts $f "#  error old ABI in use"
+    puts $f "#endif"
+    close $f
+
+    set lines [v3_target_compile $src /dev/null preprocess ""]
+    file delete $src
+
+    if [string match "" $lines] {
+        # No error message, preprocessing succeeded.
+        verbose "check_v3_cxx11_abi: `1'" 2
+        return 1
+    }
+
+    verbose "check_v3_cxx11_abi: `0'" 2
+    return 0
+}
+
 set additional_prunes ""
 
 if { [info exists env(GCC_RUNTEST_PARALLELIZE_DIR)] \