Merge topic 'WCDH_allow_unsupported'

1679fecb CompileFeatures Test: make sure the target "CompileFeatures" is always defined
98e6d1e5 Tests/Module/WCDH: make it work with only C features defined
c8703e9d WCDH: optionally omit error code for unknown compilers or compiler versions
0de9c398 WCDH: add macro to write simple replacement defines

1 files changed, 43 insertions, 79 deletions

diff --git a/Modules/WriteCompilerDetectionHeader.cmake b/Modules/WriteCompilerDetectionHeader.cmake
index ba249e1..0b16aa4 100644
--- a/Modules/WriteCompilerDetectionHeader.cmake
+++ b/Modules/WriteCompilerDetectionHeader.cmake
@@ -20,6 +20,8 @@
 #              [VERSION <version>]
 #              [PROLOG <prolog>]
 #              [EPILOG <epilog>]
+#              [ALLOW_UNKNOWN_COMPILERS]
+#              [ALLOW_UNKNOWN_COMPILER_VERSIONS]
 #    )
 #
 # The ``write_compiler_detection_header`` function generates the
@@ -81,6 +83,11 @@
 # See the :manual:`cmake-compile-features(7)` manual for information on
 # compile features.
 #
+# ``ALLOW_UNKNOWN_COMPILERS`` and ``ALLOW_UNKNOWN_COMPILER_VERSIONS`` cause
+# the module to generate conditions that treat unknown compilers as simply
+# lacking all features.  Without these options the default behavior is to
+# generate a ``#error`` for unknown compilers.
+#
 # Feature Test Macros
 # ===================
 #
@@ -232,6 +239,19 @@ function(_load_compiler_variables CompilerId lang)
   set(_compiler_id_version_compute_${CompilerId} ${_compiler_id_version_compute} PARENT_SCOPE)
 endfunction()
 
+macro(_simpledefine FEATURE_NAME FEATURE_TESTNAME FEATURE_STRING FEATURE_DEFAULT_STRING)
+  if (feature STREQUAL "${FEATURE_NAME}")
+        set(def_value "${prefix_arg}_${FEATURE_TESTNAME}")
+        string(APPEND file_content "
+#  if defined(${def_name}) && ${def_name}
+#    define ${def_value} ${FEATURE_STRING}
+#  else
+#    define ${def_value} ${FEATURE_DEFAULT_STRING}
+#  endif
+\n")
+  endif()
+endmacro()
+
 function(write_compiler_detection_header
     file_keyword file_arg
     prefix_keyword prefix_arg
@@ -242,7 +262,7 @@ function(write_compiler_detection_header
   if (NOT "x${prefix_keyword}" STREQUAL "xPREFIX")
     message(FATAL_ERROR "write_compiler_detection_header: PREFIX parameter missing.")
   endif()
-  set(options)
+  set(options ALLOW_UNKNOWN_COMPILERS ALLOW_UNKNOWN_COMPILER_VERSIONS)
   set(oneValueArgs VERSION EPILOG PROLOG OUTPUT_FILES_VAR OUTPUT_DIR)
   set(multiValueArgs COMPILERS FEATURES)
   cmake_parse_arguments(_WCD "${options}" "${oneValueArgs}" "${multiValueArgs}" ${ARGN})
@@ -426,10 +446,12 @@ function(write_compiler_detection_header
         set(compiler_file_content file_content)
       endif()
 
-      set(${compiler_file_content} "${${compiler_file_content}}
+      if(NOT _WCD_ALLOW_UNKNOWN_COMPILER_VERSIONS)
+        set(${compiler_file_content} "${${compiler_file_content}}
 #    if !(${_cmake_oldestSupported_${compiler}})
 #      error Unsupported compiler version
 #    endif\n")
+      endif()
 
       set(PREFIX ${prefix_arg}_)
       if (_need_hex_conversion)
@@ -460,67 +482,36 @@ function(write_compiler_detection_header
       endforeach()
     endforeach()
     if(pp_if STREQUAL "elif")
-      string(APPEND file_content "
+      if(_WCD_ALLOW_UNKNOWN_COMPILERS)
+        string(APPEND file_content "
+#  endif\n")
+      else()
+        string(APPEND file_content "
 #  else
 #    error Unsupported compiler
 #  endif\n")
+      endif()
     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 c_restrict)
-        set(def_value "${prefix_arg}_RESTRICT")
-        string(APPEND file_content "
-#  if ${def_name}
-#    define ${def_value} restrict
-#  else
-#    define ${def_value}
-#  endif
-\n")
-      endif()
-      if (feature STREQUAL cxx_constexpr)
-        set(def_value "${prefix_arg}_CONSTEXPR")
-        string(APPEND 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}_FINAL")
-        string(APPEND 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}_OVERRIDE")
-        string(APPEND file_content "
-#  if ${def_name}
-#    define ${def_value} override
-#  else
-#    define ${def_value}
-#  endif
-\n")
-      endif()
+      _simpledefine(c_restrict RESTRICT restrict "")
+      _simpledefine(cxx_constexpr CONSTEXPR constexpr "")
+      _simpledefine(cxx_final FINAL final "")
+      _simpledefine(cxx_override OVERRIDE override "")
       if (feature STREQUAL cxx_static_assert)
         set(def_value "${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>)")
-        string(APPEND file_content "#  if ${def_name}\n${def_standard}\n#  else\n${def_alternative}\n#  endif\n\n")
+        string(APPEND file_content "#  if defined(${def_name}) && ${def_name}\n${def_standard}\n#  else\n${def_alternative}\n#  endif\n\n")
       endif()
       if (feature STREQUAL cxx_alignas)
         set(def_value "${prefix_arg}_ALIGNAS(X)")
         string(APPEND file_content "
-#  if ${def_name}
+#  if defined(${def_name}) && ${def_name}
 #    define ${def_value} alignas(X)
 #  elif ${prefix_arg}_COMPILER_IS_GNU || ${prefix_arg}_COMPILER_IS_Clang || ${prefix_arg}_COMPILER_IS_AppleClang
 #    define ${def_value} __attribute__ ((__aligned__(X)))
@@ -534,7 +525,7 @@ function(write_compiler_detection_header
       if (feature STREQUAL cxx_alignof)
         set(def_value "${prefix_arg}_ALIGNOF(X)")
         string(APPEND file_content "
-#  if ${def_name}
+#  if defined(${def_name}) && ${def_name}
 #    define ${def_value} alignof(X)
 #  elif ${prefix_arg}_COMPILER_IS_GNU || ${prefix_arg}_COMPILER_IS_Clang || ${prefix_arg}_COMPILER_IS_AppleClang
 #    define ${def_value} __alignof__(X)
@@ -543,30 +534,12 @@ function(write_compiler_detection_header
 #  endif
 \n")
       endif()
-      if (feature STREQUAL cxx_deleted_functions)
-        set(def_value "${prefix_arg}_DELETED_FUNCTION")
-        string(APPEND 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")
-        string(APPEND file_content "
-#  if ${def_name}
-#    define ${def_value} extern
-#  else
-#    define ${def_value}
-#  endif
-\n")
-      endif()
+      _simpledefine(cxx_deleted_functions DELETED_FUNCTION "= delete" "")
+      _simpledefine(cxx_extern_templates EXTERN_TEMPLATE extern "")
       if (feature STREQUAL cxx_noexcept)
         set(def_value "${prefix_arg}_NOEXCEPT")
         string(APPEND file_content "
-#  if ${def_name}
+#  if defined(${def_name}) && ${def_name}
 #    define ${def_value} noexcept
 #    define ${def_value}_EXPR(X) noexcept(X)
 #  else
@@ -575,20 +548,11 @@ function(write_compiler_detection_header
 #  endif
 \n")
       endif()
-      if (feature STREQUAL cxx_nullptr)
-        set(def_value "${prefix_arg}_NULLPTR")
-        string(APPEND file_content "
-#  if ${def_name}
-#    define ${def_value} nullptr
-#  else
-#    define ${def_value} 0
-#  endif
-\n")
-      endif()
+      _simpledefine(cxx_nullptr NULLPTR nullptr 0)
       if (feature STREQUAL cxx_thread_local)
         set(def_value "${prefix_arg}_THREAD_LOCAL")
         string(APPEND file_content "
-#  if ${def_name}
+#  if defined(${def_name}) && ${def_name}
 #    define ${def_value} thread_local
 #  elif ${prefix_arg}_COMPILER_IS_GNU || ${prefix_arg}_COMPILER_IS_Clang || ${prefix_arg}_COMPILER_IS_AppleClang
 #    define ${def_value} __thread
@@ -604,7 +568,7 @@ function(write_compiler_detection_header
         set(def_value "${prefix_arg}_DEPRECATED")
         string(APPEND file_content "
 #  ifndef ${def_value}
-#    if ${def_name}
+#    if defined(${def_name}) && ${def_name}
 #      define ${def_value} [[deprecated]]
 #      define ${def_value}_MSG(MSG) [[deprecated(MSG)]]
 #    elif ${prefix_arg}_COMPILER_IS_GNU || ${prefix_arg}_COMPILER_IS_Clang