Index: CMakeLists.txt
===================================================================
--- CMakeLists.txt
+++ CMakeLists.txt
@@ -40,7 +40,7 @@
 option(LIBCXX_ENABLE_ASSERTIONS "Enable assertions independent of build mode." ON)
 option(LIBCXX_ENABLE_PEDANTIC "Compile with pedantic enabled." ON)
 option(LIBCXX_ENABLE_WERROR "Fail and stop if a warning is triggered." OFF)
-option(LIBCXX_ENABLE_CXX0X "Enable -std=c++0x and use of c++0x language features if the compiler supports it." ON)
+option(LIBCXX_ENABLE_CXX1Y "Enable -std=c++1y and use of c++1y language features if the compiler supports it." OFF)
 option(LIBCXX_ENABLE_SHARED "Build libc++ as a shared library." ON)
 option(LIBCXX_INSTALL_SUPPORT_HEADERS "Install libc++ support headers." ON)
 
@@ -194,9 +194,23 @@
     list(APPEND LIBCXX_CXX_REQUIRED_FLAGS -nostdinc++)
     string(REPLACE "-stdlib=libc++" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
   endif()
-  if (LIBCXX_ENABLE_CXX0X AND LIBCXX_HAS_STDCXX0X_FLAG)
-    list(APPEND LIBCXX_CXX_REQUIRED_FLAGS -std=c++0x)
+  # If c++1y has been enabled then attempt to use it. Fail if it is no supported
+  # by the compiler. Otherwise choose c++11 and ensure the compiler supports it.
+  if (LIBCXX_ENABLE_CXX1Y)
+    if (LIBCXX_HAS_STDCXX1Y_FLAG)
+      set(LIBCXX_STD_VERSION c++1y)
+    else()
+      message(FATAL_ERROR "c++1y was enabled but the compiler does not support it.")
+    endif()
+  else()
+    if (LIBCXX_HAS_STDCXX11_FLAG)
+      set(LIBCXX_STD_VERSION c++11)
+    else()
+      message(FATAL_ERROR "c++11 is required by libc++ but is not supported by the compiler")
+    endif()
   endif()
+  # LIBCXX_STD_VERSION should always be set at this point.
+  list(APPEND LIBCXX_CXX_REQUIRED_FLAGS "-std=${LIBCXX_STD_VERSION}")
 endif()
 
 macro(append_if list condition var)
Index: cmake/config-ix.cmake
===================================================================
--- cmake/config-ix.cmake
+++ cmake/config-ix.cmake
@@ -2,7 +2,8 @@
 include(CheckCXXCompilerFlag)
 
 # Check compiler flags
-check_cxx_compiler_flag(-std=c++0x            LIBCXX_HAS_STDCXX0X_FLAG)
+check_cxx_compiler_flag(-std=c++11            LIBCXX_HAS_STDCXX11_FLAG)
+check_cxx_compiler_flag(-std=c++1y            LIBCXX_HAS_STDCXX1Y_FLAG)
 check_cxx_compiler_flag(-fPIC                 LIBCXX_HAS_FPIC_FLAG)
 check_cxx_compiler_flag(-nodefaultlibs        LIBCXX_HAS_NODEFAULTLIBS_FLAG)
 check_cxx_compiler_flag(-nostdinc++           LIBCXX_HAS_NOSTDINCXX_FLAG)
Index: test/CMakeLists.txt
===================================================================
--- test/CMakeLists.txt
+++ test/CMakeLists.txt
@@ -28,7 +28,6 @@
   set(LIBCXX_BINARY_DIR ${CMAKE_BINARY_DIR})
   set(PYTHON_EXECUTABLE ${PYTHON_EXECUTABLE})
   pythonize_bool(LIBCXX_ENABLE_SHARED)
-  pythonize_bool(LIBCXX_HAS_STDCXX0X_FLAG)
 
   set(AUTO_GEN_COMMENT "## Autogenerated by libcxx configuration.\n# Do not edit!")
 
Index: test/lit.cfg
===================================================================
--- test/lit.cfg
+++ test/lit.cfg
@@ -247,18 +247,6 @@
     if libcxx_obj_root is None:
         libcxx_obj_root = libcxx_src_root
 
-cxx_has_stdcxx0x_flag_str = lit_config.params.get('cxx_has_stdcxx0x_flag', None)
-if cxx_has_stdcxx0x_flag_str is not None:
-    if cxx_has_stdcxx0x_flag_str.lower() in ('1', 'true'):
-        cxx_has_stdcxx0x_flag = True
-    elif cxx_has_stdcxx0x_flag_str.lower() in ('', '0', 'false'):
-        cxx_has_stdcxx0x_flag = False
-    else:
-        lit_config.fatal(
-            'user parameter cxx_has_stdcxx0x_flag_str should be 0 or 1')
-else:
-    cxx_has_stdcxx0x_flag = getattr(config, 'cxx_has_stdcxx0x_flag', True)
-
 # This test suite supports testing against either the system library or the
 # locally built one; the former mode is useful for testing ABI compatibility
 # between the current headers and a shipping dynamic library.
@@ -313,8 +301,18 @@
     '-I' + libcxx_src_root + '/test/support']
 library_paths = ['-L' + libcxx_obj_root + '/lib']
 compile_flags = []
-if cxx_has_stdcxx0x_flag:
-    compile_flags += ['-std=c++0x']
+
+# Try and get the std version from the command line. Fall back to default given
+# in lit.site.cfg is not present. If default is not present then force c++11.
+std = lit_config.params.get('std', None)
+if std is None:
+    std = getattr(config, 'std', None)
+    if std is None:
+        std = 'c++11'
+        lit_config.note('using default std: \'-std=c++11\'')
+else:
+    lit_config.note('using user specified std: \'-std={}\''.format(std))
+compile_flags += ['-std={}'.format(std)]
 
 # Configure extra linker parameters.
 exec_env = {}
Index: test/lit.site.cfg.in
===================================================================
--- test/lit.site.cfg.in
+++ test/lit.site.cfg.in
@@ -1,6 +1,6 @@
 @AUTO_GEN_COMMENT@
 config.cxx_under_test        = "@LIBCXX_COMPILER@"
-config.cxx_has_stdcxx0x_flag = @LIBCXX_HAS_STDCXX0X_FLAG@
+config.std                   = "@LIBCXX_STD_VERSION@"
 config.libcxx_src_root       = "@LIBCXX_SOURCE_DIR@"
 config.libcxx_obj_root       = "@LIBCXX_BINARY_DIR@"
 config.python_executable     = "@PYTHON_EXECUTABLE@"