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WCDH: introduce BARE_FEATURES
This allows defining compat versions of some C/C++ features with the name of the keyword itself, so all code can look as if it was written for the new language standard.
This commit is contained in:
Rolf Eike Beer
@@ -17,6 +17,7 @@
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# [OUTPUT_FILES_VAR <output_files_var> OUTPUT_DIR <output_dir>]
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# COMPILERS <compiler> [...]
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# FEATURES <feature> [...]
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# [BARE_FEATURES <feature> [...]]
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# [VERSION <version>]
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# [PROLOG <prolog>]
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# [EPILOG <epilog>]
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@@ -83,10 +84,14 @@
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# See the :manual:`cmake-compile-features(7)` manual for information on
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# compile features.
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#
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# ``BARE_FEATURES`` will define the compatibility macros with the name used in
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# newer versions of the language standard, so the code can use the new feature
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# name unconditionally.
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#
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# ``ALLOW_UNKNOWN_COMPILERS`` and ``ALLOW_UNKNOWN_COMPILER_VERSIONS`` cause
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# the module to generate conditions that treat unknown compilers as simply
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# lacking all features. Without these options the default behavior is to
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# generate a ``#error`` for unknown compilers.
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# generate a ``#error`` for unknown compilers and versions.
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#
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# Feature Test Macros
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# ===================
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@@ -148,20 +153,24 @@
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# ``ClimbingStats_CONSTEXPR`` macro will expand to ``constexpr``
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# if ``cxx_constexpr`` is supported.
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#
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# The following features generate corresponding symbol defines:
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# If ``BARE_FEATURES cxx_final`` was given as argument the ``final`` keyword
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# will be defined for old compilers, too.
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#
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# ========================== =================================== =================
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# Feature Define Symbol
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# ========================== =================================== =================
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# ``c_restrict`` ``<PREFIX>_RESTRICT`` ``restrict``
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# ``cxx_constexpr`` ``<PREFIX>_CONSTEXPR`` ``constexpr``
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# The following features generate corresponding symbol defines and if they
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# are available as ``BARE_FEATURES``:
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#
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# ========================== =================================== ================= ======
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# Feature Define Symbol bare
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# ========================== =================================== ================= ======
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# ``c_restrict`` ``<PREFIX>_RESTRICT`` ``restrict`` yes
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# ``cxx_constexpr`` ``<PREFIX>_CONSTEXPR`` ``constexpr`` yes
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# ``cxx_deleted_functions`` ``<PREFIX>_DELETED_FUNCTION`` ``= delete``
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# ``cxx_extern_templates`` ``<PREFIX>_EXTERN_TEMPLATE`` ``extern``
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# ``cxx_final`` ``<PREFIX>_FINAL`` ``final``
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# ``cxx_noexcept`` ``<PREFIX>_NOEXCEPT`` ``noexcept``
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# ``cxx_final`` ``<PREFIX>_FINAL`` ``final`` yes
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# ``cxx_noexcept`` ``<PREFIX>_NOEXCEPT`` ``noexcept`` yes
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# ``cxx_noexcept`` ``<PREFIX>_NOEXCEPT_EXPR(X)`` ``noexcept(X)``
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# ``cxx_override`` ``<PREFIX>_OVERRIDE`` ``override``
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# ========================== =================================== =================
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# ``cxx_override`` ``<PREFIX>_OVERRIDE`` ``override`` yes
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# ========================== =================================== ================= ======
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#
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# Compatibility Implementation Macros
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# ===================================
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@@ -195,18 +204,18 @@
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# decorator or a compiler-specific decorator such as ``__alignof__``
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# used by GNU compilers.
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#
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# ============================= ================================ =====================
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# Feature Define Symbol
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# ============================= ================================ =====================
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# ============================= ================================ ===================== ======
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# Feature Define Symbol bare
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# ============================= ================================ ===================== ======
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# ``cxx_alignas`` ``<PREFIX>_ALIGNAS`` ``alignas``
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# ``cxx_alignof`` ``<PREFIX>_ALIGNOF`` ``alignof``
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# ``cxx_nullptr`` ``<PREFIX>_NULLPTR`` ``nullptr``
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# ``cxx_nullptr`` ``<PREFIX>_NULLPTR`` ``nullptr`` yes
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# ``cxx_static_assert`` ``<PREFIX>_STATIC_ASSERT`` ``static_assert``
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# ``cxx_static_assert`` ``<PREFIX>_STATIC_ASSERT_MSG`` ``static_assert``
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# ``cxx_attribute_deprecated`` ``<PREFIX>_DEPRECATED`` ``[[deprecated]]``
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# ``cxx_attribute_deprecated`` ``<PREFIX>_DEPRECATED_MSG`` ``[[deprecated]]``
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# ``cxx_thread_local`` ``<PREFIX>_THREAD_LOCAL`` ``thread_local``
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# ============================= ================================ =====================
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# ============================= ================================ ===================== ======
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#
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# A use-case which arises with such deprecation macros is the deprecation
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# of an entire library. In that case, all public API in the library may
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@@ -252,6 +261,37 @@ macro(_simpledefine FEATURE_NAME FEATURE_TESTNAME FEATURE_STRING FEATURE_DEFAULT
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endif()
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endmacro()
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macro(_simplebaredefine FEATURE_NAME FEATURE_STRING FEATURE_DEFAULT_STRING)
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if (feature STREQUAL "${FEATURE_NAME}")
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string(APPEND file_content "
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# if !(defined(${def_name}) && ${def_name})
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# define ${FEATURE_STRING} ${FEATURE_DEFAULT_STRING}
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# endif
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\n")
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endif()
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endmacro()
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function(_check_feature_lists C_FEATURE_VAR CXX_FEATURE_VAR)
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foreach(feature ${ARGN})
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if (feature MATCHES "^c_std_")
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# ignored
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elseif (feature MATCHES "^cxx_std_")
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# ignored
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elseif (feature MATCHES "^cxx_")
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list(APPEND _langs CXX)
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list(APPEND ${CXX_FEATURE_VAR} ${feature})
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elseif (feature MATCHES "^c_")
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list(APPEND _langs C)
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list(APPEND ${C_FEATURE_VAR} ${feature})
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else()
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message(FATAL_ERROR "Unsupported feature ${feature}.")
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endif()
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endforeach()
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set(${C_FEATURE_VAR} ${${C_FEATURE_VAR}} PARENT_SCOPE)
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set(${CXX_FEATURE_VAR} ${${CXX_FEATURE_VAR}} PARENT_SCOPE)
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set(_langs ${_langs} PARENT_SCOPE)
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endfunction()
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function(write_compiler_detection_header
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file_keyword file_arg
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prefix_keyword prefix_arg
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@@ -264,13 +304,13 @@ function(write_compiler_detection_header
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endif()
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set(options ALLOW_UNKNOWN_COMPILERS ALLOW_UNKNOWN_COMPILER_VERSIONS)
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set(oneValueArgs VERSION EPILOG PROLOG OUTPUT_FILES_VAR OUTPUT_DIR)
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set(multiValueArgs COMPILERS FEATURES)
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set(multiValueArgs COMPILERS FEATURES BARE_FEATURES)
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cmake_parse_arguments(_WCD "${options}" "${oneValueArgs}" "${multiValueArgs}" ${ARGN})
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if (NOT _WCD_COMPILERS)
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message(FATAL_ERROR "Invalid arguments. write_compiler_detection_header requires at least one compiler.")
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endif()
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if (NOT _WCD_FEATURES)
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if (NOT _WCD_FEATURES AND NOT _WCD_BARE_FEATURES)
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message(FATAL_ERROR "Invalid arguments. write_compiler_detection_header requires at least one feature.")
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endif()
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@@ -377,21 +417,8 @@ function(write_compiler_detection_header
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)\n")
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endif()
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foreach(feature ${_WCD_FEATURES})
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if (feature MATCHES "^c_std_")
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# ignored
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elseif (feature MATCHES "^cxx_std_")
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# ignored
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elseif (feature MATCHES "^cxx_")
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list(APPEND _langs CXX)
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list(APPEND CXX_features ${feature})
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elseif (feature MATCHES "^c_")
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list(APPEND _langs C)
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list(APPEND C_features ${feature})
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else()
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message(FATAL_ERROR "Unsupported feature ${feature}.")
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endif()
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endforeach()
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_check_feature_lists(C_features CXX_features ${_WCD_FEATURES})
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_check_feature_lists(C_bare_features CXX_bare_features ${_WCD_BARE_FEATURES})
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list(REMOVE_DUPLICATES _langs)
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if(_WCD_OUTPUT_FILES_VAR)
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@@ -606,6 +633,29 @@ template<> struct ${prefix_arg}StaticAssert<true>{};
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endif()
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endforeach()
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foreach(feature ${${_lang}_bare_features})
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string(TOUPPER ${feature} feature_upper)
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set(feature_PP "COMPILER_${feature_upper}")
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set(def_name ${prefix_arg}_${feature_PP})
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_simplebaredefine(c_restrict restrict "")
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_simplebaredefine(cxx_constexpr constexpr "")
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_simplebaredefine(cxx_final final "")
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_simplebaredefine(cxx_override override "")
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if (feature STREQUAL cxx_nullptr)
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set(def_value "nullptr")
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string(APPEND file_content "
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# if !(defined(${def_name}) && ${def_name})
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# if ${prefix_arg}_COMPILER_IS_GNU
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# define ${def_value} __null
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# else
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# define ${def_value} 0
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# endif
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# endif
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\n")
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endif()
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_simplebaredefine(cxx_noexcept noexcept "")
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endforeach()
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string(APPEND file_content "#endif\n")
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endforeach()
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