Add the WriteCompilerDetectionHeader module.

Provide a function to write a portable header to detect compiler
features.  Generate a preprocessor #error for unknown compilers
and compiler versions whose features are not yet recorded.  This
error condition might be relaxed in the future, but for now it
is useful for verification of expectations.

40 files changed, 682 insertions, 0 deletions

diff --git a/Help/manual/cmake-modules.7.rst b/Help/manual/cmake-modules.7.rst
index 2bbe622..ecc9cc4 100644
--- a/Help/manual/cmake-modules.7.rst
+++ b/Help/manual/cmake-modules.7.rst
@@ -232,3 +232,4 @@ All Modules
    /module/UsewxWidgets
    /module/Use_wxWindows
    /module/WriteBasicConfigVersionFile
+   /module/WriteCompilerDetectionHeader
diff --git a/Help/module/WriteCompilerDetectionHeader.rst b/Help/module/WriteCompilerDetectionHeader.rst
new file mode 100644
index 0000000..4c81b48
--- /dev/null
+++ b/Help/module/WriteCompilerDetectionHeader.rst
@@ -0,0 +1 @@
+.. cmake-module:: ../../Modules/WriteCompilerDetectionHeader.cmake
diff --git a/Help/release/dev/module-WriteCompilerDetectionHeader.rst b/Help/release/dev/module-WriteCompilerDetectionHeader.rst
new file mode 100644
index 0000000..10e7b86
--- /dev/null
+++ b/Help/release/dev/module-WriteCompilerDetectionHeader.rst
@@ -0,0 +1,5 @@
+module-WriteCompilerDetectionHeader
+-----------------------------------
+
+* The :module:`WriteCompilerDetectionHeader` module was added to allow
+  creation of a portable header file for compiler optional feature detection.
diff --git a/Modules/WriteCompilerDetectionHeader.cmake b/Modules/WriteCompilerDetectionHeader.cmake
new file mode 100644
index 0000000..fd236c1
--- /dev/null
+++ b/Modules/WriteCompilerDetectionHeader.cmake
@@ -0,0 +1,401 @@
+#.rst:
+# WriteCompilerDetectionHeader
+# ----------------------------
+#
+# This module provides the function write_compiler_detection_header().
+#
+# The ``WRITE_COMPILER_DETECTION_HEADER`` function can be used to generate
+# a file suitable for preprocessor inclusion which contains macros to be
+# used in source code::
+#
+#    write_compiler_detection_header(
+#              FILE <file>
+#              PREFIX <prefix>
+#              COMPILERS <compiler> [...]
+#              FEATURES <feature> [...]
+#              [VERSION <version>]
+#              [PROLOG <prolog>]
+#              [EPILOG <epilog>]
+#    )
+#
+# The ``write_compiler_detection_header`` function generates the
+# file ``<file>`` with macros which all have the prefix ``<prefix>``.
+#
+# ``VERSION`` may be used to specify the API version to be generated.
+# Future versions of CMake may introduce alternative APIs.  A given
+# API is selected by any ``<version>`` value greater than or equal
+# to the version of CMake that introduced the given API and less
+# than the version of CMake that introduced its succeeding API.
+# The value of the :variable:`CMAKE_MINIMUM_REQUIRED_VERSION`
+# variable is used if no explicit version is specified.
+# (As of CMake version |release| there is only one API version.)
+#
+# ``PROLOG`` may be specified as text content to write at the start of the
+# header. ``EPILOG`` may be specified as text content to write at the end
+# of the header
+#
+# At least one ``<compiler>`` and one ``<feature>`` must be listed.  Compilers
+# which are known to CMake, but not specified are detected and a preprocessor
+# ``#error`` is generated for them.  A preprocessor macro matching
+# ``<PREFIX>_COMPILER_IS_<compiler>`` is generated for each compiler
+# known to CMake to contain the value ``0`` or ``1``.
+#
+# Possible compiler identifiers are documented with the
+# :variable:`CMAKE_<LANG>_COMPILER_ID` variable.
+# Available features in this version of CMake are listed in the
+# :prop_gbl:`CMAKE_CXX_KNOWN_FEATURES` global property.
+#
+# Feature Test Macros
+# ===================
+#
+# For each compiler, a preprocessor test of the compiler version is generated
+# denoting whether each feature is enabled.  A preprocessor macro
+# matching ``<PREFIX>_COMPILER_<FEATURE>``, where ``<FEATURE>`` is the
+# upper-case ``<feature>`` name, is generated to contain the value
+# ``0`` or ``1`` depending on whether the compiler in use supports the
+# feature:
+#
+# .. code-block:: cmake
+#
+#    write_compiler_detection_header(
+#      FILE climbingstats_compiler_detection.h
+#      PREFIX ClimbingStats
+#      COMPILERS GNU Clang MSVC
+#      FEATURES cxx_variadic_templates
+#    )
+#
+# .. code-block:: c++
+#
+#    #if ClimbingStats_COMPILER_CXX_VARIADIC_TEMPLATES
+#    template<typename... T>
+#    void someInterface(T t...) { /* ... */ }
+#    #else
+#    // Compatibility versions
+#    template<typename T1>
+#    void someInterface(T1 t1) { /* ... */ }
+#    template<typename T1, typename T2>
+#    void someInterface(T1 t1, T2 t2) { /* ... */ }
+#    template<typename T1, typename T2, typename T3>
+#    void someInterface(T1 t1, T2 t2, T3 t3) { /* ... */ }
+#    #endif
+#
+# Symbol Macros
+# =============
+#
+# Some additional symbol-defines are created for particular features for
+# use as symbols which may be conditionally defined empty:
+#
+# .. code-block:: c++
+#
+#    class MyClass ClimbingStats_DECL_CXX_FINAL
+#    {
+#        ClimbingStats_DECL_CXX_CONSTEXPR int someInterface() { return 42; }
+#    };
+#
+# The ``ClimbingStats_DECL_CXX_FINAL`` macro will expand to ``final`` if the
+# compiler (and its flags) support the ``cxx_final`` feature, and the
+# ``ClimbingStats_DECL_CXX_CONSTEXPR`` macro will expand to ``constexpr``
+# if ``cxx_constexpr`` is supported.
+#
+# The following features generate corresponding symbol defines:
+#
+# ========================== =================================== =================
+#         Feature                          Define                      Symbol
+# ========================== =================================== =================
+# ``cxx_constexpr``           ``<PREFIX>_CONSTEXPR``              ``constexpr``
+# ``cxx_deleted_functions``   ``<PREFIX>_DELETED_FUNCTION``       ``= delete``
+# ``cxx_extern_templates``    ``<PREFIX>_EXTERN_TEMPLATE``        ``extern``
+# ``cxx_final``               ``<PREFIX>_FINAL``                  ``final``
+# ``cxx_noexcept``            ``<PREFIX>_NOEXCEPT``               ``noexcept``
+# ``cxx_noexcept``            ``<PREFIX>_NOEXCEPT_EXPR(X)``       ``noexcept(X)``
+# ``cxx_override``            ``<PREFIX>_OVERRIDE``               ``override``
+# ========================== =================================== =================
+#
+# Compatibility Implementation Macros
+# ===================================
+#
+# Some features are suitable for wrapping in a macro with a backward
+# compatibility implementation if the compiler does not support the feature.
+#
+# When the ``cxx_static_assert`` feature is not provided by the compiler,
+# a compatibility implementation is available via the
+# ``<PREFIX>_STATIC_ASSERT(COND)`` and
+# ``<PREFIX>_STATIC_ASSERT_MSG(COND, MSG)`` function-like macros. The macros
+# expand to ``static_assert`` where that compiler feature is available, and
+# to a compatibility implementation otherwise. In the first form, the
+# condition is stringified in the message field of ``static_assert``.  In
+# the second form, the message ``MSG`` is passed to the message field of
+# ``static_assert``, or ignored if using the backward compatibility
+# implementation.
+#
+# ====================== ================================ ===================
+#         Feature                    Define                     Symbol
+# ====================== ================================ ===================
+# ``cxx_alignas``         ``<PREFIX>_ALIGNAS``             ``alignas``
+# ``cxx_alignof``         ``<PREFIX>_ALIGNOF``             ``alignof``
+# ``cxx_nullptr``         ``<PREFIX>_NULLPTR``             ``nullptr``
+# ``cxx_static_assert``   ``<PREFIX>_STATIC_ASSERT``       ``static_assert``
+# ``cxx_static_assert``   ``<PREFIX>_STATIC_ASSERT_MSG``   ``static_assert``
+# ====================== ================================ ===================
+
+
+#=============================================================================
+# Copyright 2014 Stephen Kelly <steveire@gmail.com>
+#
+# Distributed under the OSI-approved BSD License (the "License");
+# see accompanying file Copyright.txt for details.
+#
+# This software is distributed WITHOUT ANY WARRANTY; without even the
+# implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+# See the License for more information.
+#=============================================================================
+# (To distribute this file outside of CMake, substitute the full
+#  License text for the above reference.)
+
+include(${CMAKE_CURRENT_LIST_DIR}/CMakeParseArguments.cmake)
+include(${CMAKE_CURRENT_LIST_DIR}/CMakeCompilerIdDetection.cmake)
+
+function(_load_compiler_variables CompilerId lang)
+  include("${CMAKE_ROOT}/Modules/Compiler/${CompilerId}-${lang}-FeatureTests.cmake" OPTIONAL)
+  set(_cmake_oldestSupported_${CompilerId} ${_cmake_oldestSupported} PARENT_SCOPE)
+  foreach(feature ${ARGN})
+    set(_cmake_feature_test_${CompilerId}_${feature} ${_cmake_feature_test_${feature}} PARENT_SCOPE)
+  endforeach()
+endfunction()
+
+function(write_compiler_detection_header
+    file_keyword file_arg
+    prefix_keyword prefix_arg
+    )
+  if (NOT file_keyword STREQUAL FILE)
+    message(FATAL_ERROR "write_compiler_detection_header: FILE parameter missing.")
+  endif()
+  if (NOT prefix_keyword STREQUAL PREFIX)
+    message(FATAL_ERROR "write_compiler_detection_header: PREFIX parameter missing.")
+  endif()
+  set(options)
+  set(oneValueArgs VERSION EPILOG PROLOG)
+  set(multiValueArgs COMPILERS FEATURES)
+  cmake_parse_arguments(_WCD "${options}" "${oneValueArgs}" "${multiValueArgs}" ${ARGN})
+
+  if (NOT _WCD_COMPILERS)
+    message(FATAL_ERROR "Invalid arguments.  write_compiler_detection_header requires at least one compiler.")
+  endif()
+  if (NOT _WCD_FEATURES)
+    message(FATAL_ERROR "Invalid arguments.  write_compiler_detection_header requires at least one feature.")
+  endif()
+
+  if(_WCD_UNPARSED_ARGUMENTS)
+    message(FATAL_ERROR "Unparsed arguments: ${_WCD_UNPARSED_ARGUMENTS}")
+  endif()
+
+  if(NOT _WCD_VERSION)
+    set(_WCD_VERSION ${CMAKE_MINIMUM_REQUIRED_VERSION})
+  endif()
+  if (_WCD_VERSION VERSION_LESS 3.1.0) # Version which introduced this function
+    message(FATAL_ERROR "VERSION parameter too low.")
+  endif()
+
+  set(compilers
+    GNU
+  )
+  foreach(_comp ${_WCD_COMPILERS})
+    list(FIND compilers ${_comp} idx)
+    if (idx EQUAL -1)
+      message(FATAL_ERROR "Unsupported compiler ${_comp}.")
+    endif()
+  endforeach()
+
+  set(file_content "
+// This is a generated file. Do not edit!
+
+#ifndef ${prefix_arg}_COMPILER_DETECTION_H
+#define ${prefix_arg}_COMPILER_DETECTION_H
+")
+
+  if (_WCD_PROLOG)
+    set(file_content "${file_content}\n${_WCD_PROLOG}\n")
+  endif()
+
+  foreach(feature ${_WCD_FEATURES})
+    if (feature MATCHES "^cxx_")
+      list(APPEND _langs CXX)
+      list(APPEND CXX_features ${feature})
+    else()
+      message(FATAL_ERROR "Unsupported feature ${feature}.")
+    endif()
+  endforeach()
+  list(REMOVE_DUPLICATES _langs)
+
+  foreach(_lang ${_langs})
+
+    get_property(known_features GLOBAL PROPERTY CMAKE_${_lang}_KNOWN_FEATURES)
+    foreach(feature ${${_lang}_features})
+      list(FIND known_features ${feature} idx)
+      if (idx EQUAL -1)
+        message(FATAL_ERROR "Unsupported feature ${feature}.")
+      endif()
+    endforeach()
+
+    if(_lang STREQUAL CXX)
+      set(file_content "${file_content}\n#ifdef __cplusplus\n")
+    endif()
+
+    compiler_id_detection(ID_CONTENT ${_lang} PREFIX ${prefix_arg}_
+      ID_DEFINE
+    )
+
+    set(file_content "${file_content}${ID_CONTENT}\n")
+
+    set(pp_if "if")
+    foreach(compiler ${_WCD_COMPILERS})
+      _load_compiler_variables(${compiler} ${_lang} ${${_lang}_features})
+      set(file_content "${file_content}\n#  ${pp_if} ${prefix_arg}_COMPILER_IS_${compiler}\n")
+      set(file_content "${file_content}
+#    if !(${_cmake_oldestSupported_${compiler}})
+#      error Unsupported compiler version
+#    endif\n")
+      set(pp_if "elif")
+      foreach(feature ${${_lang}_features})
+        string(TOUPPER ${feature} feature_upper)
+        set(feature_PP "COMPILER_${feature_upper}")
+        set(_define_item "\n#    define ${prefix_arg}_${feature_PP} 0\n")
+        if (_cmake_feature_test_${compiler}_${feature} STREQUAL "1")
+          set(_define_item "\n#    define ${prefix_arg}_${feature_PP} 1\n")
+        elseif (_cmake_feature_test_${compiler}_${feature})
+          set(_define_item "\n#      define ${prefix_arg}_${feature_PP} 0\n")
+          set(_define_item "\n#    if ${_cmake_feature_test_${compiler}_${feature}}\n#      define ${prefix_arg}_${feature_PP} 1\n#    else${_define_item}#    endif\n")
+        endif()
+        set(file_content "${file_content}${_define_item}")
+      endforeach()
+    endforeach()
+    if(pp_if STREQUAL "elif")
+      set(file_content "${file_content}
+#  else
+#    error Unsupported compiler
+#  endif\n")
+    endif()
+    foreach(feature ${${_lang}_features})
+      string(TOUPPER ${feature} feature_upper)
+      set(feature_PP "COMPILER_${feature_upper}")
+      set(def_name ${prefix_arg}_${feature_PP})
+      if (feature STREQUAL cxx_constexpr)
+        set(def_value "${prefix_arg}_DECL_${feature_upper}")
+        set(file_content "${file_content}
+#  if ${def_name}
+#    define ${def_value} constexpr
+#  else
+#    define ${def_value}
+#  endif
+\n")
+      endif()
+      if (feature STREQUAL cxx_final)
+        set(def_value "${prefix_arg}_DECL_${feature_upper}")
+        set(file_content "${file_content}
+#  if ${def_name}
+#    define ${def_value} final
+#  else
+#    define ${def_value}
+#  endif
+\n")
+      endif()
+      if (feature STREQUAL cxx_override)
+        set(def_value "${prefix_arg}_DECL_${feature_upper}")
+        set(file_content "${file_content}
+#  if ${def_name}
+#    define ${def_value} override
+#  else
+#    define ${def_value}
+#  endif
+\n")
+      endif()
+      if (feature STREQUAL cxx_static_assert)
+        set(def_value "${prefix_arg}_STATIC_ASSERT(X)")
+        set(def_value_msg "${prefix_arg}_STATIC_ASSERT_MSG(X, MSG)")
+        set(static_assert_struct "template<bool> struct ${prefix_arg}StaticAssert;\ntemplate<> struct ${prefix_arg}StaticAssert<true>{};\n")
+        set(def_standard "#    define ${def_value} static_assert(X, #X)\n#    define ${def_value_msg} static_assert(X, MSG)")
+        set(def_alternative "${static_assert_struct}#    define ${def_value} sizeof(${prefix_arg}StaticAssert<X>)\n#    define ${def_value_msg} sizeof(${prefix_arg}StaticAssert<X>)")
+        set(file_content "${file_content}#  if ${def_name}\n${def_standard}\n#  else\n${def_alternative}\n#  endif\n\n")
+      endif()
+      if (feature STREQUAL cxx_alignas)
+        set(def_value "${prefix_arg}_ALIGNAS(X)")
+        set(file_content "${file_content}
+#  if ${def_name}
+#    define ${def_value} alignas(X)
+#  elif ${prefix_arg}_COMPILER_IS_GNU
+#    define ${def_value} __attribute__ ((__aligned__(X)))
+#  else
+#    define ${def_value}
+#  endif
+\n")
+      endif()
+      if (feature STREQUAL cxx_alignof)
+        set(def_value "${prefix_arg}_ALIGNOF(X)")
+        set(file_content "${file_content}
+#  if ${def_name}
+#    define ${def_value} alignof(X)
+#  elif ${prefix_arg}_COMPILER_IS_GNU
+#    define ${def_value} __alignof__(X)
+#  endif
+\n")
+      endif()
+      if (feature STREQUAL cxx_deleted_functions)
+        set(def_value "${prefix_arg}_DELETED_FUNCTION")
+        set(file_content "${file_content}
+#  if ${def_name}
+#    define ${def_value} = delete
+#  else
+#    define ${def_value}
+#  endif
+\n")
+      endif()
+      if (feature STREQUAL cxx_extern_templates)
+        set(def_value "${prefix_arg}_EXTERN_TEMPLATE")
+        set(file_content "${file_content}
+#  if ${def_name}
+#    define ${def_value} extern
+#  else
+#    define ${def_value}
+#  endif
+\n")
+      endif()
+      if (feature STREQUAL cxx_noexcept)
+        set(def_value "${prefix_arg}_NOEXCEPT")
+        set(file_content "${file_content}
+#  if ${def_name}
+#    define ${def_value} noexcept
+#    define ${def_value}_EXPR(X) noexcept(X)
+#  else
+#    define ${def_value}
+#    define ${def_value}_EXPR(X)
+#  endif
+\n")
+      endif()
+      if (feature STREQUAL cxx_nullptr)
+        set(def_value "${prefix_arg}_NULLPTR")
+        set(file_content "${file_content}
+#  if ${def_name}
+#    define ${def_value} nullptr
+#  else
+#    define ${def_value} static_cast<void*>(0)
+#  endif
+\n")
+      endif()
+    endforeach()
+    if(_lang STREQUAL CXX)
+      set(file_content "${file_content}#endif\n")
+    endif()
+
+  endforeach()
+
+  if (_WCD_EPILOG)
+    set(file_content "${file_content}\n${_WCD_EPILOG}\n")
+  endif()
+  set(file_content "${file_content}\n#endif")
+
+  set(CMAKE_CONFIGURABLE_FILE_CONTENT ${file_content})
+  configure_file("${CMAKE_ROOT}/Modules/CMakeConfigurableFile.in"
+    "${file_arg}"
+    @ONLY
+  )
+endfunction()
diff --git a/Tests/CMakeLists.txt b/Tests/CMakeLists.txt
index fce7887..695aacb 100644
--- a/Tests/CMakeLists.txt
+++ b/Tests/CMakeLists.txt
@@ -411,6 +411,8 @@ if(BUILD_TESTING)
   ADD_TEST_MACRO(Module.GenerateExportHeader GenerateExportHeader)
   ADD_TEST_MACRO(Module.FindDependency FindDependency)
 
+  ADD_TEST_MACRO(Module.WriteCompilerDetectionHeader WriteCompilerDetectionHeader)
+
   if (APPLE OR CMAKE_CXX_COMPILER_ID MATCHES "GNU")
     include(CheckCXXCompilerFlag)
     check_cxx_compiler_flag(-fPIE run_pic_test)
diff --git a/Tests/Module/WriteCompilerDetectionHeader/CMakeLists.txt b/Tests/Module/WriteCompilerDetectionHeader/CMakeLists.txt
new file mode 100644
index 0000000..6c5e0be
--- /dev/null
+++ b/Tests/Module/WriteCompilerDetectionHeader/CMakeLists.txt
@@ -0,0 +1,79 @@
+cmake_minimum_required(VERSION 3.0.0)
+project(WriteCompilerDetectionHeader)
+
+set(CMAKE_INCLUDE_CURRENT_DIR ON)
+
+include(WriteCompilerDetectionHeader)
+
+get_property(cxx_known_features GLOBAL PROPERTY CMAKE_CXX_KNOWN_FEATURES)
+
+write_compiler_detection_header(
+  FILE "${CMAKE_CURRENT_BINARY_DIR}/test_compiler_detection.h"
+  PREFIX TEST
+  COMPILERS GNU
+  VERSION 3.1
+  PROLOG "// something"
+  EPILOG "// more"
+  FEATURES
+    ${cxx_known_features}
+)
+
+if (NOT CMAKE_CXX_COMPILE_FEATURES)
+  file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/dummy.cpp"
+    "int main(int,char**) { return 0; }\n"
+  )
+  add_executable(WriteCompilerDetectionHeader "${CMAKE_CURRENT_BINARY_DIR}/dummy.cpp")
+
+  include(CheckCXXSourceCompiles)
+  check_cxx_source_compiles("#include \"${CMAKE_CURRENT_BINARY_DIR}/test_compiler_detection.h\"\nint main() { return 0; }\n"
+    file_include_works
+  )
+  if (file_include_works)
+    message(SEND_ERROR "Inclusion of ${CMAKE_CURRENT_BINARY_DIR}/test_compiler_detection.h was expected to cause an error, but did not.")
+  endif()
+  return()
+endif()
+
+macro(set_defines target true_defs false_defs)
+  set(defines)
+  foreach(def ${true_defs})
+    list(APPEND defines ${def}=1)
+  endforeach()
+  foreach(def ${false_defs})
+    list(APPEND defines ${def}=0)
+  endforeach()
+  target_compile_definitions(${target}
+    PRIVATE
+      ${defines}
+  )
+endmacro()
+
+if (CMAKE_CXX_COMPILER_ID STREQUAL GNU)
+  # False for C++98 mode.
+  list(APPEND false_defs EXPECTED_COMPILER_CXX_DELEGATING_CONSTRUCTORS)
+  list(APPEND false_defs EXPECTED_COMPILER_CXX_VARIADIC_TEMPLATES)
+endif()
+
+add_executable(WriteCompilerDetectionHeader main.cpp)
+set_property(TARGET WriteCompilerDetectionHeader PROPERTY CXX_STANDARD 98)
+set_defines(WriteCompilerDetectionHeader "${true_defs}" "${false_defs}")
+
+if(MSVC)
+  return() # MSVC has only one mode.
+endif()
+
+# Since GNU 4.7
+if (";${CMAKE_CXX_COMPILE_FEATURES};" MATCHES ";cxx_delegating_constructors;")
+  list(APPEND true_defs EXPECTED_COMPILER_CXX_DELEGATING_CONSTRUCTORS)
+  list(REMOVE_ITEM false_defs EXPECTED_COMPILER_CXX_DELEGATING_CONSTRUCTORS)
+endif()
+
+# Since GNU 4.4
+if (";${CMAKE_CXX_COMPILE_FEATURES};" MATCHES ";cxx_variadic_templates;")
+  list(APPEND true_defs EXPECTED_COMPILER_CXX_VARIADIC_TEMPLATES)
+  list(REMOVE_ITEM false_defs EXPECTED_COMPILER_CXX_VARIADIC_TEMPLATES)
+endif()
+
+add_executable(WriteCompilerDetectionHeader_11 main.cpp)
+set_property(TARGET WriteCompilerDetectionHeader_11 PROPERTY CXX_STANDARD 11)
+set_defines(WriteCompilerDetectionHeader_11 "${true_defs}" "${false_defs}")
diff --git a/Tests/Module/WriteCompilerDetectionHeader/main.cpp b/Tests/Module/WriteCompilerDetectionHeader/main.cpp
new file mode 100644
index 0000000..8b4ea52
--- /dev/null
+++ b/Tests/Module/WriteCompilerDetectionHeader/main.cpp
@@ -0,0 +1,19 @@
+
+#include "test_compiler_detection.h"
+
+#define JOIN_IMPL(A, B) A ## B
+#define JOIN(A, B) JOIN_IMPL(A, B)
+#define CHECK(FEATURE) (JOIN(TEST_COMPILER_, FEATURE) == JOIN(EXPECTED_COMPILER_, FEATURE))
+
+#if !CHECK(CXX_DELEGATING_CONSTRUCTORS)
+#error cxx_delegating_constructors expected availability did not match.
+#endif
+
+#if !CHECK(CXX_VARIADIC_TEMPLATES)
+#error cxx_variadic_templates expected availability did not match.
+#endif
+
+int main()
+{
+  return 0;
+}
diff --git a/Tests/RunCMake/CMakeLists.txt b/Tests/RunCMake/CMakeLists.txt
index e797a73..7f6ebf1 100644
--- a/Tests/RunCMake/CMakeLists.txt
+++ b/Tests/RunCMake/CMakeLists.txt
@@ -54,6 +54,7 @@ add_RunCMake_test(TargetObjects)
 add_RunCMake_test(TargetSources)
 add_RunCMake_test(find_dependency)
 add_RunCMake_test(CompileFeatures)
+add_RunCMake_test(WriteCompilerDetectionHeader)
 if(NOT WIN32)
   add_RunCMake_test(PositionIndependentCode)
   set(SKIP_VISIBILITY 0)
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/CMakeLists.txt b/Tests/RunCMake/WriteCompilerDetectionHeader/CMakeLists.txt
new file mode 100644
index 0000000..872338d
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/CMakeLists.txt
@@ -0,0 +1,3 @@
+cmake_minimum_required(VERSION 3.0)
+project(${RunCMake_TEST} CXX)
+include(${RunCMake_TEST}.cmake NO_POLICY_SCOPE)
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/ExtraArgs-result.txt b/Tests/RunCMake/WriteCompilerDetectionHeader/ExtraArgs-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/ExtraArgs-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/ExtraArgs-stderr.txt b/Tests/RunCMake/WriteCompilerDetectionHeader/ExtraArgs-stderr.txt
new file mode 100644
index 0000000..62c4ff1
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/ExtraArgs-stderr.txt
@@ -0,0 +1,5 @@
+CMake Error at .*Modules/WriteCompilerDetectionHeader.cmake:[0-9]+ \(message\):
+  Unparsed arguments: GarbageArg
+Call Stack \(most recent call first\):
+  ExtraArgs.cmake:4 \(write_compiler_detection_header\)
+  CMakeLists.txt:3 \(include\)
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/ExtraArgs.cmake b/Tests/RunCMake/WriteCompilerDetectionHeader/ExtraArgs.cmake
new file mode 100644
index 0000000..c2a21af
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/ExtraArgs.cmake
@@ -0,0 +1,10 @@
+
+include(WriteCompilerDetectionHeader)
+
+write_compiler_detection_header(
+  FILE "${CMAKE_CURRENT_BINARY_DIR}/somefile"
+  PREFIX Pref
+  GarbageArg
+  COMPILERS GNU
+  FEATURES cxx_final
+)
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/FileTypo-result.txt b/Tests/RunCMake/WriteCompilerDetectionHeader/FileTypo-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/FileTypo-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/FileTypo-stderr.txt b/Tests/RunCMake/WriteCompilerDetectionHeader/FileTypo-stderr.txt
new file mode 100644
index 0000000..3c0c076
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/FileTypo-stderr.txt
@@ -0,0 +1,5 @@
+CMake Error at .*Modules/WriteCompilerDetectionHeader.cmake:[0-9]+ \(message\):
+  write_compiler_detection_header: FILE parameter missing.
+Call Stack \(most recent call first\):
+  FileTypo.cmake:4 \(write_compiler_detection_header\)
+  CMakeLists.txt:3 \(include\)
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/FileTypo.cmake b/Tests/RunCMake/WriteCompilerDetectionHeader/FileTypo.cmake
new file mode 100644
index 0000000..c90eda2
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/FileTypo.cmake
@@ -0,0 +1,7 @@
+
+include(WriteCompilerDetectionHeader)
+
+write_compiler_detection_header(
+  FILE_TYPO "${CMAKE_CURRENT_BINARY_DIR}/somefile"
+  PREFIX Pref
+)
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidArgs-result.txt b/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidArgs-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidArgs-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidArgs-stderr.txt b/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidArgs-stderr.txt
new file mode 100644
index 0000000..b4d7e08
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidArgs-stderr.txt
@@ -0,0 +1,11 @@
+CMake Error at InvalidArgs.cmake:4 \(write_compiler_detection_header\):
+  write_compiler_detection_header Function invoked with incorrect arguments
+  for function named: write_compiler_detection_header
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)
++
+CMake Error at InvalidArgs.cmake:6 \(write_compiler_detection_header\):
+  write_compiler_detection_header Function invoked with incorrect arguments
+  for function named: write_compiler_detection_header
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidArgs.cmake b/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidArgs.cmake
new file mode 100644
index 0000000..cfebae1
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidArgs.cmake
@@ -0,0 +1,6 @@
+
+include(WriteCompilerDetectionHeader)
+
+write_compiler_detection_header()
+
+write_compiler_detection_header(FILE)
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidCXXFeature-result.txt b/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidCXXFeature-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidCXXFeature-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidCXXFeature-stderr.txt b/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidCXXFeature-stderr.txt
new file mode 100644
index 0000000..f34c9e1
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidCXXFeature-stderr.txt
@@ -0,0 +1,5 @@
+CMake Error at .*Modules/WriteCompilerDetectionHeader.cmake:[0-9]+ \(message\):
+  Unsupported feature cxx_not_a_feature.
+Call Stack \(most recent call first\):
+  InvalidCXXFeature.cmake:4 \(write_compiler_detection_header\)
+  CMakeLists.txt:3 \(include\)
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidCXXFeature.cmake b/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidCXXFeature.cmake
new file mode 100644
index 0000000..da870fa
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidCXXFeature.cmake
@@ -0,0 +1,10 @@
+
+include(WriteCompilerDetectionHeader)
+
+write_compiler_detection_header(
+    FILE "${CMAKE_CURRENT_BINARY_DIR}/somefile"
+    PREFIX PREF_
+    COMPILERS GNU
+    FEATURES cxx_not_a_feature
+    VERSION 3.1
+)
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidCompiler-result.txt b/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidCompiler-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidCompiler-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidCompiler-stderr.txt b/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidCompiler-stderr.txt
new file mode 100644
index 0000000..f35f9f9
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidCompiler-stderr.txt
@@ -0,0 +1,5 @@
+CMake Error at .*Modules/WriteCompilerDetectionHeader.cmake:[0-9]+ \(message\):
+  Unsupported compiler NOT_A_COMPILER.
+Call Stack \(most recent call first\):
+  InvalidCompiler.cmake:4 \(write_compiler_detection_header\)
+  CMakeLists.txt:3 \(include\)
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidCompiler.cmake b/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidCompiler.cmake
new file mode 100644
index 0000000..ecd0957
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidCompiler.cmake
@@ -0,0 +1,10 @@
+
+include(WriteCompilerDetectionHeader)
+
+write_compiler_detection_header(
+    FILE "${CMAKE_CURRENT_BINARY_DIR}/somefile"
+    PREFIX PREF_
+    COMPILERS NOT_A_COMPILER
+    FEATURES cxx_final
+    VERSION 3.1
+)
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidFeature-result.txt b/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidFeature-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidFeature-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidFeature-stderr.txt b/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidFeature-stderr.txt
new file mode 100644
index 0000000..0445744
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidFeature-stderr.txt
@@ -0,0 +1,5 @@
+CMake Error at .*Modules/WriteCompilerDetectionHeader.cmake:[0-9]+ \(message\):
+  Unsupported feature not_a_feature.
+Call Stack \(most recent call first\):
+  InvalidFeature.cmake:4 \(write_compiler_detection_header\)
+  CMakeLists.txt:3 \(include\)
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidFeature.cmake b/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidFeature.cmake
new file mode 100644
index 0000000..cd83968
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/InvalidFeature.cmake
@@ -0,0 +1,10 @@
+
+include(WriteCompilerDetectionHeader)
+
+write_compiler_detection_header(
+    FILE "${CMAKE_CURRENT_BINARY_DIR}/somefile"
+    PREFIX PREF_
+    COMPILERS GNU
+    FEATURES not_a_feature
+    VERSION 3.1
+)
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/NoCompiler-result.txt b/Tests/RunCMake/WriteCompilerDetectionHeader/NoCompiler-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/NoCompiler-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/NoCompiler-stderr.txt b/Tests/RunCMake/WriteCompilerDetectionHeader/NoCompiler-stderr.txt
new file mode 100644
index 0000000..9451348
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/NoCompiler-stderr.txt
@@ -0,0 +1,6 @@
+CMake Error at .*Modules/WriteCompilerDetectionHeader.cmake:[0-9]+ \(message\):
+  Invalid arguments.  write_compiler_detection_header requires at least one
+  compiler.
+Call Stack \(most recent call first\):
+  NoCompiler.cmake:4 \(write_compiler_detection_header\)
+  CMakeLists.txt:3 \(include\)
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/NoCompiler.cmake b/Tests/RunCMake/WriteCompilerDetectionHeader/NoCompiler.cmake
new file mode 100644
index 0000000..2dc14e9
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/NoCompiler.cmake
@@ -0,0 +1,10 @@
+
+include(WriteCompilerDetectionHeader)
+
+write_compiler_detection_header(
+    FILE "${CMAKE_CURRENT_BINARY_DIR}/somefile"
+    PREFIX PREF_
+    # COMPILERS
+    FEATURES cxx_final
+    VERSION 3.1
+)
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/NoFeature-result.txt b/Tests/RunCMake/WriteCompilerDetectionHeader/NoFeature-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/NoFeature-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/NoFeature-stderr.txt b/Tests/RunCMake/WriteCompilerDetectionHeader/NoFeature-stderr.txt
new file mode 100644
index 0000000..193f297
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/NoFeature-stderr.txt
@@ -0,0 +1,6 @@
+CMake Error at .*Modules/WriteCompilerDetectionHeader.cmake:[0-9]+ \(message\):
+  Invalid arguments.  write_compiler_detection_header requires at least one
+  feature.
+Call Stack \(most recent call first\):
+  NoFeature.cmake:4 \(write_compiler_detection_header\)
+  CMakeLists.txt:3 \(include\)
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/NoFeature.cmake b/Tests/RunCMake/WriteCompilerDetectionHeader/NoFeature.cmake
new file mode 100644
index 0000000..1fbc129
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/NoFeature.cmake
@@ -0,0 +1,10 @@
+
+include(WriteCompilerDetectionHeader)
+
+write_compiler_detection_header(
+    FILE "${CMAKE_CURRENT_BINARY_DIR}/somefile"
+    PREFIX PREF_
+    COMPILERS GNU
+    # FEATURES
+    VERSION 3.1
+)
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/OldVersion-result.txt b/Tests/RunCMake/WriteCompilerDetectionHeader/OldVersion-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/OldVersion-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/OldVersion-stderr.txt b/Tests/RunCMake/WriteCompilerDetectionHeader/OldVersion-stderr.txt
new file mode 100644
index 0000000..842eb3f
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/OldVersion-stderr.txt
@@ -0,0 +1,5 @@
+CMake Error at .*Modules/WriteCompilerDetectionHeader.cmake:[0-9]+ \(message\):
+  VERSION parameter too low.
+Call Stack \(most recent call first\):
+  OldVersion.cmake:4 \(write_compiler_detection_header\)
+  CMakeLists.txt:3 \(include\)
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/OldVersion.cmake b/Tests/RunCMake/WriteCompilerDetectionHeader/OldVersion.cmake
new file mode 100644
index 0000000..a6e3022
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/OldVersion.cmake
@@ -0,0 +1,10 @@
+
+include(WriteCompilerDetectionHeader)
+
+write_compiler_detection_header(
+  FILE "${CMAKE_CURRENT_BINARY_DIR}/somefile"
+  PREFIX Pref
+  VERSION 3.0
+  COMPILERS GNU
+  FEATURES cxx_final
+)
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/PrefixTypo-result.txt b/Tests/RunCMake/WriteCompilerDetectionHeader/PrefixTypo-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/PrefixTypo-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/PrefixTypo-stderr.txt b/Tests/RunCMake/WriteCompilerDetectionHeader/PrefixTypo-stderr.txt
new file mode 100644
index 0000000..5fdcdb8
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/PrefixTypo-stderr.txt
@@ -0,0 +1,5 @@
+CMake Error at .*Modules/WriteCompilerDetectionHeader.cmake:[0-9]+ \(message\):
+  write_compiler_detection_header: PREFIX parameter missing.
+Call Stack \(most recent call first\):
+  PrefixTypo.cmake:4 \(write_compiler_detection_header\)
+  CMakeLists.txt:3 \(include\)
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/PrefixTypo.cmake b/Tests/RunCMake/WriteCompilerDetectionHeader/PrefixTypo.cmake
new file mode 100644
index 0000000..8b6774c
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/PrefixTypo.cmake
@@ -0,0 +1,7 @@
+
+include(WriteCompilerDetectionHeader)
+
+write_compiler_detection_header(
+  FILE "${CMAKE_CURRENT_BINARY_DIR}/somefile"
+  PREFIX_TYPO Pref
+)
diff --git a/Tests/RunCMake/WriteCompilerDetectionHeader/RunCMakeTest.cmake b/Tests/RunCMake/WriteCompilerDetectionHeader/RunCMakeTest.cmake
new file mode 100644
index 0000000..be79d41
--- /dev/null
+++ b/Tests/RunCMake/WriteCompilerDetectionHeader/RunCMakeTest.cmake
@@ -0,0 +1,12 @@
+include(RunCMake)
+
+run_cmake(InvalidArgs)
+run_cmake(NoCompiler)
+run_cmake(NoFeature)
+run_cmake(FileTypo)
+run_cmake(PrefixTypo)
+run_cmake(ExtraArgs)
+run_cmake(OldVersion)
+run_cmake(InvalidCompiler)
+run_cmake(InvalidFeature)
+run_cmake(InvalidCXXFeature)