CompilerID: Compiler extensions default detection

Help/manual/cmake-variables.7.rst

@@ -553,6 +553,7 @@ Variables for Languages
    /variable/CMAKE_LANG_CREATE_SHARED_MODULE
    /variable/CMAKE_LANG_CREATE_STATIC_LIBRARY
    /variable/CMAKE_LANG_EXTENSIONS
+   /variable/CMAKE_LANG_EXTENSIONS_DEFAULT
    /variable/CMAKE_LANG_FLAGS
    /variable/CMAKE_LANG_FLAGS_CONFIG
    /variable/CMAKE_LANG_FLAGS_CONFIG_INIT

Help/variable/CMAKE_LANG_EXTENSIONS_DEFAULT.rst

@@ -0,0 +1,7 @@
+CMAKE_<LANG>_EXTENSIONS_DEFAULT
+-------------------------------
+
+.. versionadded:: 3.22
+
+Default value used when the :prop_tgt:`<LANG>_EXTENSIONS` target property is
+not set. Initialized during compiler detection to the compiler's default.

Modules/CMakeCCompiler.cmake.in

@@ -5,6 +5,7 @@ set(CMAKE_C_COMPILER_VERSION "@CMAKE_C_COMPILER_VERSION@")
 set(CMAKE_C_COMPILER_VERSION_INTERNAL "@CMAKE_C_COMPILER_VERSION_INTERNAL@")
 set(CMAKE_C_COMPILER_WRAPPER "@CMAKE_C_COMPILER_WRAPPER@")
 set(CMAKE_C_STANDARD_COMPUTED_DEFAULT "@CMAKE_C_STANDARD_COMPUTED_DEFAULT@")
+set(CMAKE_C_EXTENSIONS_COMPUTED_DEFAULT "@CMAKE_C_EXTENSIONS_COMPUTED_DEFAULT@")
 set(CMAKE_C_COMPILE_FEATURES "@CMAKE_C_COMPILE_FEATURES@")
 set(CMAKE_C90_COMPILE_FEATURES "@CMAKE_C90_COMPILE_FEATURES@")
 set(CMAKE_C99_COMPILE_FEATURES "@CMAKE_C99_COMPILE_FEATURES@")

Modules/CMakeCCompilerId.c.in

@@ -59,6 +59,17 @@ char const *info_cray = "INFO" ":" "compiler_wrapper[CrayPrgEnv]";
 const char* info_language_standard_default =
   "INFO" ":" "standard_default[" C_VERSION "]";
 
+const char* info_language_extensions_default = "INFO" ":" "extensions_default["
+// !defined(_MSC_VER) to exclude Clang's MSVC compatibility mode.
+#if (defined(__clang__) || defined(__GNUC__) ||                               \
+     defined(__TI_COMPILER_VERSION__)) &&                                     \
+  !defined(__STRICT_ANSI__) && !defined(_MSC_VER)
+  "ON"
+#else
+  "OFF"
+#endif
+"]";
+
 /*--------------------------------------------------------------------------*/
 
 #ifdef ID_VOID_MAIN
@@ -90,6 +101,7 @@ int main(int argc, char* argv[])
   require += info_cray[argc];
 #endif
   require += info_language_standard_default[argc];
+  require += info_language_extensions_default[argc];
   (void)argv;
   return require;
 }

Modules/CMakeCUDACompiler.cmake.in

@@ -6,6 +6,7 @@ set(CMAKE_CUDA_COMPILER_VERSION "@CMAKE_CUDA_COMPILER_VERSION@")
 set(CMAKE_CUDA_DEVICE_LINKER "@CMAKE_CUDA_DEVICE_LINKER@")
 set(CMAKE_CUDA_FATBINARY "@CMAKE_CUDA_FATBINARY@")
 set(CMAKE_CUDA_STANDARD_COMPUTED_DEFAULT "@CMAKE_CUDA_STANDARD_COMPUTED_DEFAULT@")
+set(CMAKE_CUDA_EXTENSIONS_COMPUTED_DEFAULT "@CMAKE_CUDA_EXTENSIONS_COMPUTED_DEFAULT@")
 set(CMAKE_CUDA_COMPILE_FEATURES "@CMAKE_CUDA_COMPILE_FEATURES@")
 set(CMAKE_CUDA03_COMPILE_FEATURES "@CMAKE_CUDA03_COMPILE_FEATURES@")
 set(CMAKE_CUDA11_COMPILE_FEATURES "@CMAKE_CUDA11_COMPILE_FEATURES@")

Modules/CMakeCUDACompilerId.cu.in

@@ -32,6 +32,16 @@ const char* info_language_standard_default = "INFO" ":" "standard_default["
 #endif
 "]";
 
+const char* info_language_extensions_default = "INFO" ":" "extensions_default["
+// !defined(_MSC_VER) to exclude Clang's MSVC compatibility mode.
+#if (defined(__clang__) || defined(__GNUC__)) && !defined(__STRICT_ANSI__) && \
+  !defined(_MSC_VER)
+  "ON"
+#else
+  "OFF"
+#endif
+"]";
+
 /*--------------------------------------------------------------------------*/
 
 int main(int argc, char* argv[])
@@ -49,6 +59,7 @@ int main(int argc, char* argv[])
   require += info_simulate_version[argc];
 #endif
   require += info_language_standard_default[argc];
+  require += info_language_extensions_default[argc];
   (void)argv;
   return require;
 }

Modules/CMakeCXXCompiler.cmake.in

@@ -5,6 +5,7 @@ set(CMAKE_CXX_COMPILER_VERSION "@CMAKE_CXX_COMPILER_VERSION@")
 set(CMAKE_CXX_COMPILER_VERSION_INTERNAL "@CMAKE_CXX_COMPILER_VERSION_INTERNAL@")
 set(CMAKE_CXX_COMPILER_WRAPPER "@CMAKE_CXX_COMPILER_WRAPPER@")
 set(CMAKE_CXX_STANDARD_COMPUTED_DEFAULT "@CMAKE_CXX_STANDARD_COMPUTED_DEFAULT@")
+set(CMAKE_CXX_EXTENSIONS_COMPUTED_DEFAULT "@CMAKE_CXX_EXTENSIONS_COMPUTED_DEFAULT@")
 set(CMAKE_CXX_COMPILE_FEATURES "@CMAKE_CXX_COMPILE_FEATURES@")
 set(CMAKE_CXX98_COMPILE_FEATURES "@CMAKE_CXX98_COMPILE_FEATURES@")
 set(CMAKE_CXX11_COMPILE_FEATURES "@CMAKE_CXX11_COMPILE_FEATURES@")

Modules/CMakeCXXCompilerId.cpp.in

@@ -65,6 +65,17 @@ const char* info_language_standard_default = "INFO" ":" "standard_default["
 #endif
 "]";
 
+const char* info_language_extensions_default = "INFO" ":" "extensions_default["
+// !defined(_MSC_VER) to exclude Clang's MSVC compatibility mode.
+#if (defined(__clang__) || defined(__GNUC__) ||                               \
+     defined(__TI_COMPILER_VERSION__)) &&                                     \
+  !defined(__STRICT_ANSI__) && !defined(_MSC_VER)
+  "ON"
+#else
+  "OFF"
+#endif
+"]";
+
 /*--------------------------------------------------------------------------*/
 
 int main(int argc, char* argv[])
@@ -88,6 +99,7 @@ int main(int argc, char* argv[])
   require += info_cray[argc];
 #endif
   require += info_language_standard_default[argc];
+  require += info_language_extensions_default[argc];
   (void)argv;
   return require;
 }

Modules/CMakeDetermineCompilerId.cmake

@@ -267,6 +267,7 @@ function(CMAKE_DETERMINE_COMPILER_ID lang flagvar src)
   set(CMAKE_${lang}_SIMULATE_ID "${CMAKE_${lang}_SIMULATE_ID}" PARENT_SCOPE)
   set(CMAKE_${lang}_SIMULATE_VERSION "${CMAKE_${lang}_SIMULATE_VERSION}" PARENT_SCOPE)
   set(CMAKE_${lang}_STANDARD_COMPUTED_DEFAULT "${CMAKE_${lang}_STANDARD_COMPUTED_DEFAULT}" PARENT_SCOPE)
+  set(CMAKE_${lang}_EXTENSIONS_COMPUTED_DEFAULT "${CMAKE_${lang}_EXTENSIONS_COMPUTED_DEFAULT}" PARENT_SCOPE)
   set(CMAKE_${lang}_COMPILER_PRODUCED_OUTPUT "${COMPILER_${lang}_PRODUCED_OUTPUT}" PARENT_SCOPE)
   set(CMAKE_${lang}_COMPILER_PRODUCED_FILES "${COMPILER_${lang}_PRODUCED_FILES}" PARENT_SCOPE)
 endfunction()
@@ -884,6 +885,9 @@ function(CMAKE_DETERMINE_COMPILER_ID_CHECK lang file)
       if("${info}" MATCHES "INFO:standard_default\\[([^]\"]*)\\]")
         set(CMAKE_${lang}_STANDARD_COMPUTED_DEFAULT "${CMAKE_MATCH_1}")
       endif()
+      if("${info}" MATCHES "INFO:extensions_default\\[([^]\"]*)\\]")
+        set(CMAKE_${lang}_EXTENSIONS_COMPUTED_DEFAULT "${CMAKE_MATCH_1}")
+      endif()
     endforeach()
 
     # Construct compiler version from components if needed.
@@ -993,6 +997,7 @@ function(CMAKE_DETERMINE_COMPILER_ID_CHECK lang file)
   set(CMAKE_${lang}_SIMULATE_VERSION "${CMAKE_${lang}_SIMULATE_VERSION}" PARENT_SCOPE)
   set(COMPILER_QNXNTO "${COMPILER_QNXNTO}" PARENT_SCOPE)
   set(CMAKE_${lang}_STANDARD_COMPUTED_DEFAULT "${CMAKE_${lang}_STANDARD_COMPUTED_DEFAULT}" PARENT_SCOPE)
+  set(CMAKE_${lang}_EXTENSIONS_COMPUTED_DEFAULT "${CMAKE_${lang}_EXTENSIONS_COMPUTED_DEFAULT}" PARENT_SCOPE)
 endfunction()
 
 #-----------------------------------------------------------------------------

Modules/CMakeHIPCompiler.cmake.in

@@ -2,6 +2,7 @@ set(CMAKE_HIP_COMPILER "@CMAKE_HIP_COMPILER@")
 set(CMAKE_HIP_COMPILER_ID "@CMAKE_HIP_COMPILER_ID@")
 set(CMAKE_HIP_COMPILER_VERSION "@CMAKE_HIP_COMPILER_VERSION@")
 set(CMAKE_HIP_STANDARD_COMPUTED_DEFAULT "@CMAKE_HIP_STANDARD_COMPUTED_DEFAULT@")
+set(CMAKE_HIP_EXTENSIONS_COMPUTED_DEFAULT "@CMAKE_HIP_EXTENSIONS_COMPUTED_DEFAULT@")
 set(CMAKE_HIP_COMPILE_FEATURES "@CMAKE_HIP_COMPILE_FEATURES@")
 set(CMAKE_HIP98_COMPILE_FEATURES "@CMAKE_HIP03_COMPILE_FEATURES@")
 set(CMAKE_HIP11_COMPILE_FEATURES "@CMAKE_HIP11_COMPILE_FEATURES@")

Modules/CMakeHIPCompilerId.hip.in

@@ -32,6 +32,14 @@ const char* info_language_standard_default = "INFO" ":" "standard_default["
 #endif
 "]";
 
+const char* info_language_extensions_default = "INFO" ":" "extensions_default["
+#if (defined(__clang__) || defined(__GNUC__)) && !defined(__STRICT_ANSI__)
+  "ON"
+#else
+  "OFF"
+#endif
+"]";
+
 /*--------------------------------------------------------------------------*/
 
 int main(int argc, char* argv[])
@@ -49,6 +57,7 @@ int main(int argc, char* argv[])
   require += info_simulate_version[argc];
 #endif
   require += info_language_standard_default[argc];
+  require += info_language_extensions_default[argc];
   (void)argv;
   return require;
 }

Modules/CMakeOBJCCompiler.cmake.in

@@ -5,6 +5,7 @@ set(CMAKE_OBJC_COMPILER_VERSION "@CMAKE_OBJC_COMPILER_VERSION@")
 set(CMAKE_OBJC_COMPILER_VERSION_INTERNAL "@CMAKE_OBJC_COMPILER_VERSION_INTERNAL@")
 set(CMAKE_OBJC_COMPILER_WRAPPER "@CMAKE_OBJC_COMPILER_WRAPPER@")
 set(CMAKE_OBJC_STANDARD_COMPUTED_DEFAULT "@CMAKE_OBJC_STANDARD_COMPUTED_DEFAULT@")
+set(CMAKE_OBJC_EXTENSIONS_COMPUTED_DEFAULT "@CMAKE_OBJC_EXTENSIONS_COMPUTED_DEFAULT@")
 set(CMAKE_OBJC_COMPILE_FEATURES "@CMAKE_OBJC_COMPILE_FEATURES@")
 set(CMAKE_OBJC90_COMPILE_FEATURES "@CMAKE_OBJC90_COMPILE_FEATURES@")
 set(CMAKE_OBJC99_COMPILE_FEATURES "@CMAKE_OBJC99_COMPILE_FEATURES@")

Modules/CMakeOBJCCompilerId.m.in

@@ -41,6 +41,14 @@ char const* qnxnto = "INFO" ":" "qnxnto[]";
 const char* info_language_standard_default =
   "INFO" ":" "standard_default[" C_VERSION "]";
 
+const char* info_language_extensions_default = "INFO" ":" "extensions_default["
+#if (defined(__clang__) || defined(__GNUC__)) && !defined(__STRICT_ANSI__)
+  "ON"
+#else
+  "OFF"
+#endif
+"]";
+
 /*--------------------------------------------------------------------------*/
 
 int main(int argc, char* argv[])
@@ -62,6 +70,7 @@ int main(int argc, char* argv[])
   require += info_simulate_version[argc];
 #endif
   require += info_language_standard_default[argc];
+  require += info_language_extensions_default[argc];
   (void)argv;
   return require;
 }

Modules/CMakeOBJCXXCompiler.cmake.in

@@ -5,6 +5,7 @@ set(CMAKE_OBJCXX_COMPILER_VERSION "@CMAKE_OBJCXX_COMPILER_VERSION@")
 set(CMAKE_OBJCXX_COMPILER_VERSION_INTERNAL "@CMAKE_OBJCXX_COMPILER_VERSION_INTERNAL@")
 set(CMAKE_OBJCXX_COMPILER_WRAPPER "@CMAKE_OBJCXX_COMPILER_WRAPPER@")
 set(CMAKE_OBJCXX_STANDARD_COMPUTED_DEFAULT "@CMAKE_OBJCXX_STANDARD_COMPUTED_DEFAULT@")
+set(CMAKE_OBJCXX_EXTENSIONS_COMPUTED_DEFAULT "@CMAKE_OBJCXX_EXTENSIONS_COMPUTED_DEFAULT@")
 set(CMAKE_OBJCXX_COMPILE_FEATURES "@CMAKE_OBJCXX_COMPILE_FEATURES@")
 set(CMAKE_OBJCXX98_COMPILE_FEATURES "@CMAKE_OBJCXX98_COMPILE_FEATURES@")
 set(CMAKE_OBJCXX11_COMPILE_FEATURES "@CMAKE_OBJCXX11_COMPILE_FEATURES@")

Modules/CMakeOBJCXXCompilerId.mm.in

@@ -45,6 +45,14 @@ const char* info_language_standard_default = "INFO" ":" "standard_default["
 #endif
 "]";
 
+const char* info_language_extensions_default = "INFO" ":" "extensions_default["
+#if (defined(__clang__) || defined(__GNUC__)) && !defined(__STRICT_ANSI__)
+  "ON"
+#else
+  "OFF"
+#endif
+"]";
+
 /*--------------------------------------------------------------------------*/
 
 int main(int argc, char* argv[])
@@ -65,6 +73,7 @@ int main(int argc, char* argv[])
   require += info_simulate_version[argc];
 #endif
   require += info_language_standard_default[argc];
+  require += info_language_extensions_default[argc];
   (void)argv;
   return require;
 }

Modules/Compiler/CMakeCommonCompilerMacros.cmake

@@ -38,20 +38,26 @@ macro(__compiler_check_default_language_standard lang stdver1 std1)
   # support for language standards, then don't bother.
   if (CMAKE_${lang}_COMPILER_VERSION VERSION_GREATER_EQUAL "${stdver1}")
     if (NOT CMAKE_${lang}_COMPILER_FORCED)
-      if (NOT CMAKE_${lang}_STANDARD_COMPUTED_DEFAULT)
-        message(FATAL_ERROR "CMAKE_${lang}_STANDARD_COMPUTED_DEFAULT should be set for ${CMAKE_${lang}_COMPILER_ID} (${CMAKE_${lang}_COMPILER}) version ${CMAKE_${lang}_COMPILER_VERSION}")
+      if (NOT CMAKE_${lang}_STANDARD_COMPUTED_DEFAULT OR NOT DEFINED CMAKE_${lang}_EXTENSIONS_COMPUTED_DEFAULT)
+        message(FATAL_ERROR "CMAKE_${lang}_STANDARD_COMPUTED_DEFAULT and CMAKE_${lang}_EXTENSIONS_COMPUTED_DEFAULT should be set for ${CMAKE_${lang}_COMPILER_ID} (${CMAKE_${lang}_COMPILER}) version ${CMAKE_${lang}_COMPILER_VERSION}")
       endif ()
       set(CMAKE_${lang}_STANDARD_DEFAULT ${CMAKE_${lang}_STANDARD_COMPUTED_DEFAULT})
+      set(CMAKE_${lang}_EXTENSIONS_DEFAULT ${CMAKE_${lang}_EXTENSIONS_COMPUTED_DEFAULT})
     else ()
       list(REVERSE __std_ver_pairs)
       foreach (__std_ver_pair IN LISTS __std_ver_pairs)
         string(REGEX MATCH "([^ ]+) (.+)" __std_ver_pair "${__std_ver_pair}")
         set(__stdver ${CMAKE_MATCH_1})
         set(__std ${CMAKE_MATCH_2})
-        if (CMAKE_${lang}_COMPILER_VERSION VERSION_GREATER_EQUAL __stdver AND
-          NOT DEFINED CMAKE_${lang}_STANDARD_DEFAULT)
-          # Compiler id was forced so just guess the default standard level.
-          set(CMAKE_${lang}_STANDARD_DEFAULT ${__std})
+        # Compiler id was forced so just guess the defaults.
+        if (CMAKE_${lang}_COMPILER_VERSION VERSION_GREATER_EQUAL __stdver)
+          if(NOT DEFINED CMAKE_${lang}_EXTENSIONS_DEFAULT)
+            # Currently known compilers default to enabling extensions.
+            set(CMAKE_${lang}_EXTENSIONS_DEFAULT ON)
+          endif()
+          if(NOT DEFINED CMAKE_${lang}_STANDARD_DEFAULT)
+            set(CMAKE_${lang}_STANDARD_DEFAULT ${__std})
+          endif()
         endif ()
         unset(__std)
         unset(__stdver)