CUDA, CXX, OBJCXX: C++23 support with Clang 12

Clang 12 landed initial support for C++23 language mode flag -std={c|gnu}++2b
in commit 6627a3c2873fdf7ccba1a1573371079be48b36e8.

20 files changed, 76 insertions, 15 deletions

diff --git a/Help/prop_gbl/CMAKE_CUDA_KNOWN_FEATURES.rst b/Help/prop_gbl/CMAKE_CUDA_KNOWN_FEATURES.rst
index e8e3148..6bbb870 100644
--- a/Help/prop_gbl/CMAKE_CUDA_KNOWN_FEATURES.rst
+++ b/Help/prop_gbl/CMAKE_CUDA_KNOWN_FEATURES.rst
@@ -30,3 +30,6 @@ The features known to this version of CMake are:
 
 ``cuda_std_20``
   Compiler mode is at least CUDA/C++ 20.
+
+``cuda_std_23``
+  Compiler mode is at least CUDA/C++ 23.
diff --git a/Help/prop_gbl/CMAKE_CXX_KNOWN_FEATURES.rst b/Help/prop_gbl/CMAKE_CXX_KNOWN_FEATURES.rst
index bac3274..73c0b34 100644
--- a/Help/prop_gbl/CMAKE_CXX_KNOWN_FEATURES.rst
+++ b/Help/prop_gbl/CMAKE_CXX_KNOWN_FEATURES.rst
@@ -37,6 +37,8 @@ but it does not necessarily imply complete conformance to that standard.
 ``cxx_std_20``
   Compiler mode is at least C++ 20.
 
+``cxx_std_23``
+  Compiler mode is at least C++ 23.
 
 Low level individual compile features
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/Help/prop_tgt/CUDA_STANDARD.rst b/Help/prop_tgt/CUDA_STANDARD.rst
index fcc4725..6517035 100644
--- a/Help/prop_tgt/CUDA_STANDARD.rst
+++ b/Help/prop_tgt/CUDA_STANDARD.rst
@@ -9,7 +9,7 @@ This property specifies the CUDA/C++ standard whose features are requested
 to build this target.  For some compilers, this results in adding a
 flag such as ``-std=gnu++11`` to the compile line.
 
-Supported values are ``98``, ``03``, ``11``, ``14``, ``17``, ``20``.
+Supported values are ``98``, ``03``, ``11``, ``14``, ``17``, ``20``, ``23``.
 
 If the value requested does not result in a compile flag being added for
 the compiler in use, a previous standard flag will be added instead.  This
diff --git a/Help/prop_tgt/CXX_STANDARD.rst b/Help/prop_tgt/CXX_STANDARD.rst
index f322ffe..be0dab5 100644
--- a/Help/prop_tgt/CXX_STANDARD.rst
+++ b/Help/prop_tgt/CXX_STANDARD.rst
@@ -11,7 +11,7 @@ flag such as ``-std=gnu++11`` to the compile line.  For compilers that
 have no notion of a standard level, such as Microsoft Visual C++ before
 2015 Update 3, this has no effect.
 
-Supported values are ``98``, ``11``, ``14``, ``17``, and ``20``.
+Supported values are ``98``, ``11``, ``14``, ``17``, ``20``, ``23``.
 
 If the value requested does not result in a compile flag being added for
 the compiler in use, a previous standard flag will be added instead.  This
diff --git a/Help/prop_tgt/OBJCXX_STANDARD.rst b/Help/prop_tgt/OBJCXX_STANDARD.rst
index 1067153..96088af 100644
--- a/Help/prop_tgt/OBJCXX_STANDARD.rst
+++ b/Help/prop_tgt/OBJCXX_STANDARD.rst
@@ -9,7 +9,7 @@ This property specifies the ObjC++ standard whose features are requested
 to build this target.  For some compilers, this results in adding a
 flag such as ``-std=gnu++11`` to the compile line.
 
-Supported values are ``98``, ``11``, ``14``, ``17``, and ``20``.
+Supported values are ``98``, ``11``, ``14``, ``17``, ``20``, ``23``.
 
 If the value requested does not result in a compile flag being added for
 the compiler in use, a previous standard flag will be added instead.  This
diff --git a/Help/release/dev/cpp-cuda-23.rst b/Help/release/dev/cpp-cuda-23.rst
new file mode 100644
index 0000000..dc7c3b1
--- /dev/null
+++ b/Help/release/dev/cpp-cuda-23.rst
@@ -0,0 +1,7 @@
+cpp-cuda-23
+-----------
+
+* :prop_tgt:`CXX_STANDARD`, :prop_tgt:`CUDA_STANDARD`,
+  :prop_tgt:`OBJCXX_STANDARD` and the
+  :manual:`Compile Features <cmake-compile-features(7)>` functionality gained
+  support for C++23.
diff --git a/Modules/CMakeCUDACompiler.cmake.in b/Modules/CMakeCUDACompiler.cmake.in
index d4e6e2e..56ae732 100644
--- a/Modules/CMakeCUDACompiler.cmake.in
+++ b/Modules/CMakeCUDACompiler.cmake.in
@@ -12,6 +12,7 @@ set(CMAKE_CUDA11_COMPILE_FEATURES "@CMAKE_CUDA11_COMPILE_FEATURES@")
 set(CMAKE_CUDA14_COMPILE_FEATURES "@CMAKE_CUDA14_COMPILE_FEATURES@")
 set(CMAKE_CUDA17_COMPILE_FEATURES "@CMAKE_CUDA17_COMPILE_FEATURES@")
 set(CMAKE_CUDA20_COMPILE_FEATURES "@CMAKE_CUDA20_COMPILE_FEATURES@")
+set(CMAKE_CUDA23_COMPILE_FEATURES "@CMAKE_CUDA23_COMPILE_FEATURES@")
 
 set(CMAKE_CUDA_PLATFORM_ID "@CMAKE_CUDA_PLATFORM_ID@")
 set(CMAKE_CUDA_SIMULATE_ID "@CMAKE_CUDA_SIMULATE_ID@")
diff --git a/Modules/CMakeCUDACompilerId.cu.in b/Modules/CMakeCUDACompilerId.cu.in
index 2055de2..91039e5 100644
--- a/Modules/CMakeCUDACompilerId.cu.in
+++ b/Modules/CMakeCUDACompilerId.cu.in
@@ -17,7 +17,9 @@ char const* info_simulate = "INFO" ":" "simulate[" SIMULATE_ID "]";
 @CMAKE_CUDA_COMPILER_ID_ERROR_FOR_TEST@
 
 const char* info_language_dialect_default = "INFO" ":" "dialect_default["
-#if __cplusplus > 201703L
+#if __cplusplus > 202002L
+  "23"
+#elif __cplusplus > 201703L
   "20"
 #elif __cplusplus >= 201703L
   "17"
diff --git a/Modules/CMakeCXXCompiler.cmake.in b/Modules/CMakeCXXCompiler.cmake.in
index a235ebb..92ae2ab 100644
--- a/Modules/CMakeCXXCompiler.cmake.in
+++ b/Modules/CMakeCXXCompiler.cmake.in
@@ -11,6 +11,7 @@ set(CMAKE_CXX11_COMPILE_FEATURES "@CMAKE_CXX11_COMPILE_FEATURES@")
 set(CMAKE_CXX14_COMPILE_FEATURES "@CMAKE_CXX14_COMPILE_FEATURES@")
 set(CMAKE_CXX17_COMPILE_FEATURES "@CMAKE_CXX17_COMPILE_FEATURES@")
 set(CMAKE_CXX20_COMPILE_FEATURES "@CMAKE_CXX20_COMPILE_FEATURES@")
+set(CMAKE_CXX23_COMPILE_FEATURES "@CMAKE_CXX23_COMPILE_FEATURES@")
 
 set(CMAKE_CXX_PLATFORM_ID "@CMAKE_CXX_PLATFORM_ID@")
 set(CMAKE_CXX_SIMULATE_ID "@CMAKE_CXX_SIMULATE_ID@")
diff --git a/Modules/CMakeCXXCompilerId.cpp.in b/Modules/CMakeCXXCompilerId.cpp.in
index 672fff8..49d9f0a 100644
--- a/Modules/CMakeCXXCompilerId.cpp.in
+++ b/Modules/CMakeCXXCompilerId.cpp.in
@@ -44,7 +44,9 @@ char const *info_cray = "INFO" ":" "compiler_wrapper[CrayPrgEnv]";
 #endif
 
 const char* info_language_dialect_default = "INFO" ":" "dialect_default["
-#if CXX_STD > 201703L
+#if CXX_STD > 202002L
+  "23"
+#elif CXX_STD > 201703L
   "20"
 #elif CXX_STD >= 201703L
   "17"
diff --git a/Modules/CMakeDetermineCompileFeatures.cmake b/Modules/CMakeDetermineCompileFeatures.cmake
index b50e5f1..c03a85f 100644
--- a/Modules/CMakeDetermineCompileFeatures.cmake
+++ b/Modules/CMakeDetermineCompileFeatures.cmake
@@ -50,6 +50,7 @@ function(cmake_determine_compile_features lang)
     set(CMAKE_CXX14_COMPILE_FEATURES)
     set(CMAKE_CXX17_COMPILE_FEATURES)
     set(CMAKE_CXX20_COMPILE_FEATURES)
+    set(CMAKE_CXX23_COMPILE_FEATURES)
 
     include("${CMAKE_ROOT}/Modules/Internal/FeatureTesting.cmake")
 
@@ -60,6 +61,9 @@ function(cmake_determine_compile_features lang)
       return()
     endif()
 
+    if (CMAKE_CXX20_COMPILE_FEATURES AND CMAKE_CXX23_COMPILE_FEATURES)
+      list(REMOVE_ITEM CMAKE_CXX23_COMPILE_FEATURES ${CMAKE_CXX20_COMPILE_FEATURES})
+    endif()
     if (CMAKE_CXX17_COMPILE_FEATURES AND CMAKE_CXX20_COMPILE_FEATURES)
       list(REMOVE_ITEM CMAKE_CXX20_COMPILE_FEATURES ${CMAKE_CXX17_COMPILE_FEATURES})
     endif()
@@ -80,6 +84,7 @@ function(cmake_determine_compile_features lang)
         ${CMAKE_CXX14_COMPILE_FEATURES}
         ${CMAKE_CXX17_COMPILE_FEATURES}
         ${CMAKE_CXX20_COMPILE_FEATURES}
+        ${CMAKE_CXX23_COMPILE_FEATURES}
       )
     endif()
 
@@ -89,6 +94,7 @@ function(cmake_determine_compile_features lang)
     set(CMAKE_CXX14_COMPILE_FEATURES ${CMAKE_CXX14_COMPILE_FEATURES} PARENT_SCOPE)
     set(CMAKE_CXX17_COMPILE_FEATURES ${CMAKE_CXX17_COMPILE_FEATURES} PARENT_SCOPE)
     set(CMAKE_CXX20_COMPILE_FEATURES ${CMAKE_CXX20_COMPILE_FEATURES} PARENT_SCOPE)
+    set(CMAKE_CXX23_COMPILE_FEATURES ${CMAKE_CXX23_COMPILE_FEATURES} PARENT_SCOPE)
 
     message(CHECK_PASS "done")
 
@@ -100,6 +106,7 @@ function(cmake_determine_compile_features lang)
     set(CMAKE_CUDA14_COMPILE_FEATURES)
     set(CMAKE_CUDA17_COMPILE_FEATURES)
     set(CMAKE_CUDA20_COMPILE_FEATURES)
+    set(CMAKE_CUDA23_COMPILE_FEATURES)
 
     include("${CMAKE_ROOT}/Modules/Internal/FeatureTesting.cmake")
 
@@ -110,7 +117,10 @@ function(cmake_determine_compile_features lang)
       return()
     endif()
 
-  if (CMAKE_CUDA17_COMPILE_FEATURES AND CMAKE_CUDA20_COMPILE_FEATURES)
+    if (CMAKE_CUDA20_COMPILE_FEATURES AND CMAKE_CUDA23_COMPILE_FEATURES)
+      list(REMOVE_ITEM CMAKE_CUDA23_COMPILE_FEATURES ${CMAKE_CUDA20_COMPILE_FEATURES})
+    endif()
+    if (CMAKE_CUDA17_COMPILE_FEATURES AND CMAKE_CUDA20_COMPILE_FEATURES)
       list(REMOVE_ITEM CMAKE_CUDA20_COMPILE_FEATURES ${CMAKE_CUDA17_COMPILE_FEATURES})
     endif()
     if (CMAKE_CUDA14_COMPILE_FEATURES AND CMAKE_CUDA17_COMPILE_FEATURES)
@@ -130,6 +140,7 @@ function(cmake_determine_compile_features lang)
         ${CMAKE_CUDA14_COMPILE_FEATURES}
         ${CMAKE_CUDA17_COMPILE_FEATURES}
         ${CMAKE_CUDA20_COMPILE_FEATURES}
+        ${CMAKE_CUDA23_COMPILE_FEATURES}
       )
     endif()
 
@@ -139,6 +150,7 @@ function(cmake_determine_compile_features lang)
     set(CMAKE_CUDA14_COMPILE_FEATURES ${CMAKE_CUDA14_COMPILE_FEATURES} PARENT_SCOPE)
     set(CMAKE_CUDA17_COMPILE_FEATURES ${CMAKE_CUDA17_COMPILE_FEATURES} PARENT_SCOPE)
     set(CMAKE_CUDA20_COMPILE_FEATURES ${CMAKE_CUDA20_COMPILE_FEATURES} PARENT_SCOPE)
+    set(CMAKE_CUDA23_COMPILE_FEATURES ${CMAKE_CUDA23_COMPILE_FEATURES} PARENT_SCOPE)
 
     message(CHECK_PASS "done")
 
diff --git a/Modules/CMakeOBJCXXCompiler.cmake.in b/Modules/CMakeOBJCXXCompiler.cmake.in
index 18eb7ff..a24582b 100644
--- a/Modules/CMakeOBJCXXCompiler.cmake.in
+++ b/Modules/CMakeOBJCXXCompiler.cmake.in
@@ -11,6 +11,7 @@ set(CMAKE_OBJCXX11_COMPILE_FEATURES "@CMAKE_OBJCXX11_COMPILE_FEATURES@")
 set(CMAKE_OBJCXX14_COMPILE_FEATURES "@CMAKE_OBJCXX14_COMPILE_FEATURES@")
 set(CMAKE_OBJCXX17_COMPILE_FEATURES "@CMAKE_OBJCXX17_COMPILE_FEATURES@")
 set(CMAKE_OBJCXX20_COMPILE_FEATURES "@CMAKE_OBJCXX20_COMPILE_FEATURES@")
+set(CMAKE_OBJCXX23_COMPILE_FEATURES "@CMAKE_OBJCXX23_COMPILE_FEATURES@")
 
 set(CMAKE_OBJCXX_PLATFORM_ID "@CMAKE_OBJCXX_PLATFORM_ID@")
 set(CMAKE_OBJCXX_SIMULATE_ID "@CMAKE_OBJCXX_SIMULATE_ID@")
diff --git a/Modules/CMakeOBJCXXCompilerId.mm.in b/Modules/CMakeOBJCXXCompilerId.mm.in
index fe04de1..e2ac35d 100644
--- a/Modules/CMakeOBJCXXCompilerId.mm.in
+++ b/Modules/CMakeOBJCXXCompilerId.mm.in
@@ -30,7 +30,9 @@ char const* qnxnto = "INFO" ":" "qnxnto[]";
 #endif
 
 const char* info_language_dialect_default = "INFO" ":" "dialect_default["
-#if CXX_STD > 201703L
+#if CXX_STD > 202002L
+  "23"
+#elfif CXX_STD > 201703L
   "20"
 #elif CXX_STD >= 201703L
   "17"
diff --git a/Modules/Compiler/CMakeCommonCompilerMacros.cmake b/Modules/Compiler/CMakeCommonCompilerMacros.cmake
index 7a30ac6..cd897c5 100644
--- a/Modules/Compiler/CMakeCommonCompilerMacros.cmake
+++ b/Modules/Compiler/CMakeCommonCompilerMacros.cmake
@@ -93,6 +93,9 @@ endmacro()
 # Define to allow compile features to be automatically determined
 macro(cmake_record_cxx_compile_features)
   set(_result 0)
+  if(_result EQUAL 0 AND DEFINED CMAKE_CXX23_STANDARD_COMPILE_OPTION)
+    _has_compiler_features_cxx(23)
+  endif()
   if(_result EQUAL 0 AND DEFINED CMAKE_CXX20_STANDARD_COMPILE_OPTION)
     _has_compiler_features_cxx(20)
   endif()
@@ -127,6 +130,9 @@ endmacro()
 
 macro(cmake_record_cuda_compile_features)
   set(_result 0)
+  if(_result EQUAL 0 AND DEFINED CMAKE_CUDA23_STANDARD_COMPILE_OPTION)
+    _has_compiler_features_cuda(23)
+  endif()
   if(_result EQUAL 0 AND DEFINED CMAKE_CUDA20_STANDARD_COMPILE_OPTION)
     _has_compiler_features_cuda(20)
   endif()
diff --git a/Modules/Compiler/Clang.cmake b/Modules/Compiler/Clang.cmake
index 0e4cded..9f900df 100644
--- a/Modules/Compiler/Clang.cmake
+++ b/Modules/Compiler/Clang.cmake
@@ -165,6 +165,11 @@ macro(__compiler_clang_cxx_standards lang)
 
     unset(_clang_version_std17)
 
+    if(NOT CMAKE_${lang}_COMPILER_VERSION VERSION_LESS 12.0)
+      set(CMAKE_${lang}23_STANDARD_COMPILE_OPTION "-std=c++2b")
+      set(CMAKE_${lang}23_EXTENSION_COMPILE_OPTION "-std=gnu++2b")
+    endif()
+
     if("x${CMAKE_${lang}_SIMULATE_ID}" STREQUAL "xMSVC")
       # The MSVC standard library requires C++14, and MSVC itself has no
       # notion of operating in a mode not aware of at least that standard.
@@ -215,6 +220,8 @@ macro(__compiler_clang_cxx_standards lang)
     set(CMAKE_${lang}17_EXTENSION_COMPILE_OPTION "")
     set(CMAKE_${lang}20_STANDARD_COMPILE_OPTION "")
     set(CMAKE_${lang}20_EXTENSION_COMPILE_OPTION "")
+    set(CMAKE_${lang}23_STANDARD_COMPILE_OPTION "")
+    set(CMAKE_${lang}23_EXTENSION_COMPILE_OPTION "")
 
     # There is no meaningful default for this
     set(CMAKE_${lang}_STANDARD_DEFAULT "")
@@ -230,6 +237,7 @@ macro(__compiler_clang_cxx_standards lang)
         cxx_std_14
         cxx_std_17
         cxx_std_20
+        cxx_std_23
         )
       _record_compiler_features(${lang} "" CMAKE_${lang}_COMPILE_FEATURES)
     endmacro()
diff --git a/Source/cmStandardLevelResolver.cxx b/Source/cmStandardLevelResolver.cxx
index 8672f61..5d8ccf1 100644
--- a/Source/cmStandardLevelResolver.cxx
+++ b/Source/cmStandardLevelResolver.cxx
@@ -311,19 +311,19 @@ std::unordered_map<std::string, StanardLevelComputer> StandardComputerMapping =
                             std::vector<std::string>{ "90", "99", "11" } } },
     { "CXX",
       StanardLevelComputer{
-        "CXX", std::vector<int>{ 98, 11, 14, 17, 20 },
-        std::vector<std::string>{ "98", "11", "14", "17", "20" } } },
+        "CXX", std::vector<int>{ 98, 11, 14, 17, 20, 23 },
+        std::vector<std::string>{ "98", "11", "14", "17", "20", "23" } } },
     { "CUDA",
       StanardLevelComputer{
-        "CUDA", std::vector<int>{ 03, 11, 14, 17, 20 },
-        std::vector<std::string>{ "03", "11", "14", "17", "20" } } },
+        "CUDA", std::vector<int>{ 03, 11, 14, 17, 20, 23 },
+        std::vector<std::string>{ "03", "11", "14", "17", "20", "23" } } },
     { "OBJC",
       StanardLevelComputer{ "OBJC", std::vector<int>{ 90, 99, 11 },
                             std::vector<std::string>{ "90", "99", "11" } } },
     { "OBJCXX",
       StanardLevelComputer{
-        "OBJCXX", std::vector<int>{ 98, 11, 14, 17, 20 },
-        std::vector<std::string>{ "98", "11", "14", "17", "20" } } },
+        "OBJCXX", std::vector<int>{ 98, 11, 14, 17, 20, 23 },
+        std::vector<std::string>{ "98", "11", "14", "17", "20", "23" } } },
   };
 }
 
diff --git a/Source/cmake.h b/Source/cmake.h
index 914b827..d936f28 100644
--- a/Source/cmake.h
+++ b/Source/cmake.h
@@ -811,6 +811,7 @@ private:
   F(cxx_std_14)                                                               \
   F(cxx_std_17)                                                               \
   F(cxx_std_20)                                                               \
+  F(cxx_std_23)                                                               \
   FOR_EACH_CXX98_FEATURE(F)                                                   \
   FOR_EACH_CXX11_FEATURE(F)                                                   \
   FOR_EACH_CXX14_FEATURE(F)
@@ -820,4 +821,5 @@ private:
   F(cuda_std_11)                                                              \
   F(cuda_std_14)                                                              \
   F(cuda_std_17)                                                              \
-  F(cuda_std_20)
+  F(cuda_std_20)                                                              \
+  F(cuda_std_23)
diff --git a/Tests/CompileFeatures/CMakeLists.txt b/Tests/CompileFeatures/CMakeLists.txt
index ef9198d..0838532 100644
--- a/Tests/CompileFeatures/CMakeLists.txt
+++ b/Tests/CompileFeatures/CMakeLists.txt
@@ -268,6 +268,7 @@ if (CMAKE_CXX_COMPILE_FEATURES)
     if (std_flag_idx EQUAL -1)
       add_executable(default_dialect default_dialect.cpp)
       target_compile_definitions(default_dialect PRIVATE
+        DEFAULT_CXX23=$<EQUAL:${CMAKE_CXX_STANDARD_DEFAULT},23>
         DEFAULT_CXX20=$<EQUAL:${CMAKE_CXX_STANDARD_DEFAULT},20>
         DEFAULT_CXX17=$<EQUAL:${CMAKE_CXX_STANDARD_DEFAULT},17>
         DEFAULT_CXX14=$<EQUAL:${CMAKE_CXX_STANDARD_DEFAULT},14>
@@ -349,6 +350,7 @@ else()
       HAVE_CXX_STD_14=$<COMPILE_FEATURES:cxx_std_14>
       HAVE_CXX_STD_17=$<COMPILE_FEATURES:cxx_std_17>
       HAVE_CXX_STD_20=$<COMPILE_FEATURES:cxx_std_20>
+      HAVE_CXX_STD_23=$<COMPILE_FEATURES:cxx_std_23>
     )
   endif()
 
diff --git a/Tests/CompileFeatures/default_dialect.cpp b/Tests/CompileFeatures/default_dialect.cpp
index e6b3ff6..bd504ff 100644
--- a/Tests/CompileFeatures/default_dialect.cpp
+++ b/Tests/CompileFeatures/default_dialect.cpp
@@ -18,7 +18,11 @@ struct Outputter;
 #  define CXX_STD __cplusplus
 #endif
 
-#if DEFAULT_CXX20
+#if DEFAULT_CXX23
+#  if CXX_STD <= 202002L
+Outputter<CXX_STD> o;
+#  endif
+#elif DEFAULT_CXX20
 #  if CXX_STD <= 201703L
 Outputter<CXX_STD> o;
 #  endif
diff --git a/Tests/CompileFeatures/genex_test.cpp b/Tests/CompileFeatures/genex_test.cpp
index 53dce62..9c3910e 100644
--- a/Tests/CompileFeatures/genex_test.cpp
+++ b/Tests/CompileFeatures/genex_test.cpp
@@ -21,6 +21,12 @@
 #  if HAVE_CXX_STD_17 && !defined(ALLOW_LATER_STANDARDS)
 #    error HAVE_CXX_STD_17 is true with CXX_STANDARD == 11
 #  endif
+#  if HAVE_CXX_STD_20 && !defined(ALLOW_LATER_STANDARDS)
+#    error HAVE_CXX_STD_20 is true with CXX_STANDARD == 11
+#  endif
+#  if HAVE_CXX_STD_23 && !defined(ALLOW_LATER_STANDARDS)
+#    error HAVE_CXX_STD_23 is true with CXX_STANDARD == 11
+#  endif
 #endif
 
 #if !HAVE_OVERRIDE_CONTROL