Make C++ feature checks extensible

Turn the feature check for cxx11_unordered_map into a function such that
we can use it for other features as well.  Drop the 11 suffix, as we may
want to check features from other standards.

CMakeLists.txt

@@ -67,7 +67,7 @@ if(NOT DEFINED CMAKE_CXX_STANDARD AND NOT CMake_NO_CXX_STANDARD)
   endif()
 endif()
 if(NOT CMake_TEST_EXTERNAL_CMAKE)
-  include(${CMake_SOURCE_DIR}/Source/Checks/cm_cxx11_unordered_map.cmake)
+  include(${CMake_SOURCE_DIR}/Source/Checks/cm_cxx_features.cmake)
 endif()
 
 # option to set the internal encoding of CMake to UTF-8

Source/Checks/cm_cxx11_unordered_map.cmake

@@ -1,25 +0,0 @@
-
-if(CMAKE_CXX_STANDARD AND NOT DEFINED CMake_HAVE_CXX11_UNORDERED_MAP)
-  message(STATUS "Checking if compiler supports C++11 unordered_map")
-  try_compile(CMake_HAVE_CXX11_UNORDERED_MAP
-    ${CMAKE_CURRENT_BINARY_DIR}
-    ${CMAKE_CURRENT_LIST_DIR}/cm_cxx11_unordered_map.cpp
-    CMAKE_FLAGS -DCMAKE_CXX_STANDARD=${CMAKE_CXX_STANDARD}
-    OUTPUT_VARIABLE OUTPUT
-    )
-  if(CMake_HAVE_CXX11_UNORDERED_MAP)
-    message(STATUS "Checking if compiler supports C++11 unordered_map - yes")
-    file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeOutput.log
-      "Determining if compiler supports C++11 unordered_map passed with the following output:\n"
-      "${OUTPUT}\n"
-      "\n"
-      )
-  else()
-    message(STATUS "Checking if compiler supports C++11 unordered_map - no")
-    file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeError.log
-      "Determining if compiler supports C++11 unordered_map failed with the following output:\n"
-      "${OUTPUT}\n"
-      "\n"
-      )
-  endif()
-endif()

Source/Checks/cm_cxx_features.cmake

@@ -0,0 +1,36 @@
+
+function(cm_check_cxx_feature name)
+  string(TOUPPER ${name} FEATURE)
+  if(NOT DEFINED CMake_HAVE_CXX_${FEATURE})
+    message(STATUS "Checking if compiler supports C++ ${name}")
+    try_compile(CMake_HAVE_CXX_${FEATURE}
+      ${CMAKE_CURRENT_BINARY_DIR}
+      ${CMAKE_CURRENT_LIST_DIR}/cm_cxx_${name}.cxx
+      CMAKE_FLAGS -DCMAKE_CXX_STANDARD=${CMAKE_CXX_STANDARD}
+      OUTPUT_VARIABLE OUTPUT
+      )
+    # If using the feature causes warnings, treat it as broken/unavailable.
+    if(OUTPUT MATCHES "warning")
+      set(CMake_HAVE_CXX_${FEATURE} OFF CACHE INTERNAL "TRY_COMPILE" FORCE)
+    endif()
+    if(CMake_HAVE_CXX_${FEATURE})
+      message(STATUS "Checking if compiler supports C++ ${name} - yes")
+      file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeOutput.log
+        "Determining if compiler supports C++ ${name} passed with the following output:\n"
+        "${OUTPUT}\n"
+        "\n"
+        )
+    else()
+      message(STATUS "Checking if compiler supports C++ ${name} - no")
+      file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeError.log
+        "Determining if compiler supports C++ ${name} failed with the following output:\n"
+        "${OUTPUT}\n"
+        "\n"
+        )
+    endif()
+  endif()
+endfunction()
+
+if(CMAKE_CXX_STANDARD)
+  cm_check_cxx_feature(unordered_map)
+endif()

Source/cmConfigure.cmake.h.in

@@ -29,7 +29,7 @@
 #cmakedefine CMAKE_USE_ELF_PARSER
 #cmakedefine CMAKE_USE_MACH_PARSER
 #cmakedefine CMAKE_ENCODING_UTF8
-#cmakedefine CMake_HAVE_CXX11_UNORDERED_MAP
+#cmakedefine CMake_HAVE_CXX_UNORDERED_MAP
 #define CMAKE_BIN_DIR "/@CMAKE_BIN_DIR@"
 #define CMAKE_DATA_DIR "/@CMAKE_DATA_DIR@"
 

Source/cmDefinitions.h

@@ -17,7 +17,7 @@
 #include "cmLinkedTree.h"
 
 #if defined(CMAKE_BUILD_WITH_CMAKE)
-#ifdef CMake_HAVE_CXX11_UNORDERED_MAP
+#ifdef CMake_HAVE_CXX_UNORDERED_MAP
 #include <unordered_map>
 #else
 #include "cmsys/hash_map.hxx"
@@ -92,7 +92,7 @@ private:
   static Def NoDef;
 
 #if defined(CMAKE_BUILD_WITH_CMAKE)
-#ifdef CMake_HAVE_CXX11_UNORDERED_MAP
+#ifdef CMake_HAVE_CXX_UNORDERED_MAP
   typedef std::unordered_map<std::string, Def> MapType;
 #else
   typedef cmsys::hash_map<std::string, Def> MapType;

Source/cmFileTimeComparison.cxx

@@ -13,7 +13,7 @@
 
 // Use a hash table to avoid duplicate file time checks from disk.
 #if defined(CMAKE_BUILD_WITH_CMAKE)
-#ifdef CMake_HAVE_CXX11_UNORDERED_MAP
+#ifdef CMake_HAVE_CXX_UNORDERED_MAP
 #include <unordered_map>
 #else
 #include <cmsys/hash_map.hxx>
@@ -47,13 +47,13 @@ private:
   {
   public:
     size_t operator()(const std::string& s) const { return h(s.c_str()); }
-#ifdef CMake_HAVE_CXX11_UNORDERED_MAP
+#ifdef CMake_HAVE_CXX_UNORDERED_MAP
     std::hash<const char*> h;
 #else
     cmsys::hash<const char*> h;
 #endif
   };
-#ifdef CMake_HAVE_CXX11_UNORDERED_MAP
+#ifdef CMake_HAVE_CXX_UNORDERED_MAP
   typedef std::unordered_map<std::string,
 #else
   typedef cmsys::hash_map<std::string,

Source/cmGlobalGenerator.h

@@ -25,7 +25,7 @@
 
 #if defined(CMAKE_BUILD_WITH_CMAKE)
 #include "cmFileLockPool.h"
-#ifdef CMake_HAVE_CXX11_UNORDERED_MAP
+#ifdef CMake_HAVE_CXX_UNORDERED_MAP
 #include <unordered_map>
 #else
 #include <cmsys/hash_map.hxx>
@@ -433,7 +433,7 @@ protected:
 
 private:
 #if defined(CMAKE_BUILD_WITH_CMAKE)
-#ifdef CMake_HAVE_CXX11_UNORDERED_MAP
+#ifdef CMake_HAVE_CXX_UNORDERED_MAP
   typedef std::unordered_map<std::string, cmTarget*> TargetMap;
   typedef std::unordered_map<std::string, cmGeneratorTarget*>
     GeneratorTargetMap;

Source/cmMakefile.h

@@ -31,7 +31,7 @@
 #include <cmsys/RegularExpression.hxx>
 #include <cmsys/auto_ptr.hxx>
 #if defined(CMAKE_BUILD_WITH_CMAKE)
-#ifdef CMake_HAVE_CXX11_UNORDERED_MAP
+#ifdef CMake_HAVE_CXX_UNORDERED_MAP
 #include <unordered_map>
 #else
 #include <cmsys/hash_map.hxx>
@@ -796,7 +796,7 @@ protected:
   // libraries, classes, and executables
   mutable cmTargets Targets;
 #if defined(CMAKE_BUILD_WITH_CMAKE)
-#ifdef CMake_HAVE_CXX11_UNORDERED_MAP
+#ifdef CMake_HAVE_CXX_UNORDERED_MAP
   typedef std::unordered_map<std::string, cmTarget*> TargetMap;
 #else
   typedef cmsys::hash_map<std::string, cmTarget*> TargetMap;
@@ -915,7 +915,7 @@ private:
 
 // A map for fast output to input look up.
 #if defined(CMAKE_BUILD_WITH_CMAKE)
-#ifdef CMake_HAVE_CXX11_UNORDERED_MAP
+#ifdef CMake_HAVE_CXX_UNORDERED_MAP
   typedef std::unordered_map<std::string, cmSourceFile*> OutputToSourceMap;
 #else
   typedef cmsys::hash_map<std::string, cmSourceFile*> OutputToSourceMap;

Source/cmTarget.h

@@ -21,7 +21,7 @@
 
 #include <cmsys/auto_ptr.hxx>
 #if defined(CMAKE_BUILD_WITH_CMAKE)
-#ifdef CMake_HAVE_CXX11_UNORDERED_MAP
+#ifdef CMake_HAVE_CXX_UNORDERED_MAP
 #include <unordered_map>
 #else
 #include <cmsys/hash_map.hxx>
@@ -331,7 +331,7 @@ private:
 };
 
 #ifdef CMAKE_BUILD_WITH_CMAKE
-#ifdef CMake_HAVE_CXX11_UNORDERED_MAP
+#ifdef CMake_HAVE_CXX_UNORDERED_MAP
 typedef std::unordered_map<std::string, cmTarget> cmTargets;
 #else
 typedef cmsys::hash_map<std::string, cmTarget> cmTargets;