From 4f7d9eef51da4a72fd7c7a17bcbbcf83ffad3216 Mon Sep 17 00:00:00 2001
From: Brad King <brad.king@kitware.com>
Date: Tue, 8 Aug 2017 10:46:00 -0400
Subject: Features: Fix COMPILE_FEATURES genex for C++ 14 and 17 features

When `CXX_STANDARD` is not at least 14 or 17, features enabled by the
compiler for those standards should not be reported as existing by the
`COMPILE_FEATURES` genex.  Fix the implementation and add a test.
---
 Source/cmMakefile.cxx                | 12 ++++++++++++
 Tests/CompileFeatures/CMakeLists.txt |  8 ++++++++
 Tests/CompileFeatures/genex_test.cpp | 12 ++++++++++++
 3 files changed, 32 insertions(+)

diff --git a/Source/cmMakefile.cxx b/Source/cmMakefile.cxx
index f077459..cb6cf2d 100644
--- a/Source/cmMakefile.cxx
+++ b/Source/cmMakefile.cxx
@@ -4381,6 +4381,18 @@ bool cmMakefile::HaveCxxStandardAvailable(cmTarget const* target,
                    cmStrCmp(existingCxxStandard))
     : cmArrayEnd(CXX_STANDARDS);
 
+  if (needCxx17 &&
+      existingCxxIt < std::find_if(cmArrayBegin(CXX_STANDARDS),
+                                   cmArrayEnd(CXX_STANDARDS),
+                                   cmStrCmp("17"))) {
+    return false;
+  }
+  if (needCxx14 &&
+      existingCxxIt < std::find_if(cmArrayBegin(CXX_STANDARDS),
+                                   cmArrayEnd(CXX_STANDARDS),
+                                   cmStrCmp("14"))) {
+    return false;
+  }
   if (needCxx11 &&
       existingCxxIt < std::find_if(cmArrayBegin(CXX_STANDARDS),
                                    cmArrayEnd(CXX_STANDARDS),
diff --git a/Tests/CompileFeatures/CMakeLists.txt b/Tests/CompileFeatures/CMakeLists.txt
index 4a5558d..b560acd 100644
--- a/Tests/CompileFeatures/CMakeLists.txt
+++ b/Tests/CompileFeatures/CMakeLists.txt
@@ -428,6 +428,14 @@ else()
     HAVE_FINAL=$<COMPILE_FEATURES:cxx_final>
     HAVE_INHERITING_CONSTRUCTORS_AND_FINAL=$<COMPILE_FEATURES:cxx_inheriting_constructors,cxx_final>
   )
+  if (CMAKE_CXX_STANDARD_DEFAULT)
+    target_compile_definitions(CompileFeaturesGenex PRIVATE
+      TEST_CXX_STD
+      HAVE_CXX_STD_11=$<COMPILE_FEATURES:cxx_std_11>
+      HAVE_CXX_STD_14=$<COMPILE_FEATURES:cxx_std_14>
+      HAVE_CXX_STD_17=$<COMPILE_FEATURES:cxx_std_17>
+    )
+  endif()
 
   add_executable(CompileFeaturesGenex2 genex_test.cpp)
   target_compile_features(CompileFeaturesGenex2 PRIVATE cxx_std_11)
diff --git a/Tests/CompileFeatures/genex_test.cpp b/Tests/CompileFeatures/genex_test.cpp
index 5ae8a78..5303e73 100644
--- a/Tests/CompileFeatures/genex_test.cpp
+++ b/Tests/CompileFeatures/genex_test.cpp
@@ -11,6 +11,18 @@
 #error EXPECT_OVERRIDE_CONTROL not defined
 #endif
 
+#ifdef TEST_CXX_STD
+#if !HAVE_CXX_STD_11
+#error HAVE_CXX_STD_11 is false with CXX_STANDARD == 11
+#endif
+#if HAVE_CXX_STD_14
+#error HAVE_CXX_STD_14 is true with CXX_STANDARD == 11
+#endif
+#if HAVE_CXX_STD_17
+#error HAVE_CXX_STD_17 is true with CXX_STANDARD == 11
+#endif
+#endif
+
 #if !HAVE_OVERRIDE_CONTROL
 #if EXPECT_OVERRIDE_CONTROL
 #error "Expect override control feature"
-- 
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