From 7e748417bc8e06caa8eb0b6a6258b7d24cc22bfb Mon Sep 17 00:00:00 2001
From: Stephen Kelly <steveire@gmail.com>
Date: Thu, 3 Apr 2014 00:08:49 +0200
Subject: [PATCH] Features: Add cxx_decltype.

---
 Help/variable/CMAKE_CXX_KNOWN_FEATURES.rst  | 5 +++++
 Modules/Compiler/GNU-CXX-FeatureTests.cmake | 1 +
 Source/cmMakefile.cxx                       | 1 +
 Tests/CompileFeatures/cxx_decltype.cpp      | 7 +++++++
 4 files changed, 14 insertions(+)
 create mode 100644 Tests/CompileFeatures/cxx_decltype.cpp

diff --git a/Help/variable/CMAKE_CXX_KNOWN_FEATURES.rst b/Help/variable/CMAKE_CXX_KNOWN_FEATURES.rst
index 4a685730f..97689dcb2 100644
--- a/Help/variable/CMAKE_CXX_KNOWN_FEATURES.rst
+++ b/Help/variable/CMAKE_CXX_KNOWN_FEATURES.rst
@@ -22,6 +22,11 @@ The features known to this version of CMake are:
 
   .. _N2235: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2235.pdf
 
+``cxx_decltype``
+  Decltype, as defined in N2343_.
+
+  .. _N2343: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2343.pdf
+
 ``cxx_delegating_constructors``
   Delegating constructors, as defined in N1986_.
 
diff --git a/Modules/Compiler/GNU-CXX-FeatureTests.cmake b/Modules/Compiler/GNU-CXX-FeatureTests.cmake
index c451b7e0d..de328c438 100644
--- a/Modules/Compiler/GNU-CXX-FeatureTests.cmake
+++ b/Modules/Compiler/GNU-CXX-FeatureTests.cmake
@@ -30,5 +30,6 @@ set(_cmake_feature_test_cxx_variadic_templates "${GNU44_CXX11}")
 # http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2555.pdf
 # TODO: Should be supported by GNU 4.3
 set(GNU43_CXX11 "${_oldestSupported} && __cplusplus >= 201103L")
+set(_cmake_feature_test_cxx_decltype "${GNU43_CXX11}")
 set(_cmake_feature_test_cxx_static_assert "${GNU43_CXX11}")
 set(_oldestSupported)
diff --git a/Source/cmMakefile.cxx b/Source/cmMakefile.cxx
index 12d88e41e..6ce3c16b1 100644
--- a/Source/cmMakefile.cxx
+++ b/Source/cmMakefile.cxx
@@ -44,6 +44,7 @@
 #define FOR_EACH_CXX_FEATURE(F) \
   F(cxx_auto_type) \
   F(cxx_constexpr) \
+  F(cxx_decltype) \
   F(cxx_delegating_constructors) \
   F(cxx_final) \
   F(cxx_override) \
diff --git a/Tests/CompileFeatures/cxx_decltype.cpp b/Tests/CompileFeatures/cxx_decltype.cpp
new file mode 100644
index 000000000..24ec51e84
--- /dev/null
+++ b/Tests/CompileFeatures/cxx_decltype.cpp
@@ -0,0 +1,7 @@
+
+int someFunc()
+{
+  int i = 0;
+  decltype(i) other = 0;
+  return other;
+}