10 files changed, 129 insertions, 10 deletions
diff --git a/Modules/Compiler/CMakeCommonCompilerMacros.cmake b/Modules/Compiler/CMakeCommonCompilerMacros.cmake
index 684fd30..ad464c7 100644
--- a/Modules/Compiler/CMakeCommonCompilerMacros.cmake
+++ b/Modules/Compiler/CMakeCommonCompilerMacros.cmake
@@ -78,6 +78,9 @@ 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_CXX20_STANDARD_COMPILE_OPTION)
+    _record_compiler_features_cxx(20)
+  endif()
   if(_result EQUAL 0 AND DEFINED CMAKE_CXX17_STANDARD_COMPILE_OPTION)
     _record_compiler_features_cxx(17)
   endif()
diff --git a/Modules/Compiler/Clang-CXX.cmake b/Modules/Compiler/Clang-CXX.cmake
index efc68b3..e99011b 100644
--- a/Modules/Compiler/Clang-CXX.cmake
+++ b/Modules/Compiler/Clang-CXX.cmake
@@ -32,12 +32,52 @@ if(NOT "x${CMAKE_CXX_SIMULATE_ID}" STREQUAL "xMSVC")
     set(CMAKE_CXX14_EXTENSION_COMPILE_OPTION "-std=gnu++1y")
   endif()
 
-  if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 3.5)
+  set(_clang_version_std17 5.0)
+  if(CMAKE_SYSTEM_NAME STREQUAL "Android")
+    set(_clang_version_std17 6.0)
+  endif()
+
+  if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS "${_clang_version_std17}")
+    set(CMAKE_CXX17_STANDARD_COMPILE_OPTION "-std=c++17")
+    set(CMAKE_CXX17_EXTENSION_COMPILE_OPTION "-std=gnu++17")
+  elseif (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 3.5)
     set(CMAKE_CXX17_STANDARD_COMPILE_OPTION "-std=c++1z")
     set(CMAKE_CXX17_EXTENSION_COMPILE_OPTION "-std=gnu++1z")
   endif()
+
+  if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS "${_clang_version_std17}")
+    set(CMAKE_CXX20_STANDARD_COMPILE_OPTION "-std=c++2a")
+    set(CMAKE_CXX20_EXTENSION_COMPILE_OPTION "-std=gnu++2a")
+  endif()
+
+  unset(_clang_version_std17)
+
+  __compiler_check_default_language_standard(CXX 2.1 98)
+elseif(CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 3.9
+    AND CMAKE_CXX_SIMULATE_VERSION VERSION_GREATER_EQUAL 19.0)
+  # This version of clang-cl and the MSVC version it simulates have
+  # support for -std: flags.
+  set(CMAKE_CXX98_STANDARD_COMPILE_OPTION "")
+  set(CMAKE_CXX98_EXTENSION_COMPILE_OPTION "")
+  set(CMAKE_CXX11_STANDARD_COMPILE_OPTION "")
+  set(CMAKE_CXX11_EXTENSION_COMPILE_OPTION "")
+  set(CMAKE_CXX14_STANDARD_COMPILE_OPTION "-std:c++14")
+  set(CMAKE_CXX14_EXTENSION_COMPILE_OPTION "-std:c++14")
+  if (CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 6.0)
+    set(CMAKE_CXX17_STANDARD_COMPILE_OPTION "-std:c++17")
+    set(CMAKE_CXX17_EXTENSION_COMPILE_OPTION "-std:c++17")
+    set(CMAKE_CXX20_STANDARD_COMPILE_OPTION "-std:c++latest")
+    set(CMAKE_CXX20_EXTENSION_COMPILE_OPTION "-std:c++latest")
+  else()
+    set(CMAKE_CXX17_STANDARD_COMPILE_OPTION "-std:c++latest")
+    set(CMAKE_CXX17_EXTENSION_COMPILE_OPTION "-std:c++latest")
+  endif()
+
+  __compiler_check_default_language_standard(CXX 3.9 14)
 else()
-  # clang-cl does not know these options because it behaves like cl.exe
+  # This version of clang-cl, or the MSVC version it simulates, does not have
+  # language standards.  Set these options as empty strings so the feature
+  # test infrastructure can at least check to see if they are defined.
   set(CMAKE_CXX98_STANDARD_COMPILE_OPTION "")
   set(CMAKE_CXX98_EXTENSION_COMPILE_OPTION "")
   set(CMAKE_CXX11_STANDARD_COMPILE_OPTION "")
@@ -46,10 +86,24 @@ else()
   set(CMAKE_CXX14_EXTENSION_COMPILE_OPTION "")
   set(CMAKE_CXX17_STANDARD_COMPILE_OPTION "")
   set(CMAKE_CXX17_EXTENSION_COMPILE_OPTION "")
-endif()
+  set(CMAKE_CXX20_STANDARD_COMPILE_OPTION "")
+  set(CMAKE_CXX20_EXTENSION_COMPILE_OPTION "")
 
-if(NOT "x${CMAKE_CXX_SIMULATE_ID}" STREQUAL "xMSVC")
-  __compiler_check_default_language_standard(CXX 2.1 98)
-else()
+  # There is no meaningful default for this
   set(CMAKE_CXX_STANDARD_DEFAULT "")
+
+  # There are no compiler modes so we only need to test features once.
+  # Override the default macro for this special case.  Pretend that
+  # all language standards are available so that at least compilation
+  # can be attempted.
+  macro(cmake_record_cxx_compile_features)
+    list(APPEND CMAKE_CXX_COMPILE_FEATURES
+      cxx_std_98
+      cxx_std_11
+      cxx_std_14
+      cxx_std_17
+      cxx_std_20
+      )
+    _record_compiler_features(CXX "" CMAKE_CXX_COMPILE_FEATURES)
+  endmacro()
 endif()
diff --git a/Modules/Compiler/GNU-CXX.cmake b/Modules/Compiler/GNU-CXX.cmake
index 4f1f30e..0058223 100644
--- a/Modules/Compiler/GNU-CXX.cmake
+++ b/Modules/Compiler/GNU-CXX.cmake
@@ -33,9 +33,17 @@ elseif (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.8)
   set(CMAKE_CXX14_EXTENSION_COMPILE_OPTION "-std=gnu++1y")
 endif()
 
-if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 5.1)
+if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 8.0)
+  set(CMAKE_CXX17_STANDARD_COMPILE_OPTION "-std=c++17")
+  set(CMAKE_CXX17_EXTENSION_COMPILE_OPTION "-std=gnu++17")
+elseif (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 5.1)
   set(CMAKE_CXX17_STANDARD_COMPILE_OPTION "-std=c++1z")
   set(CMAKE_CXX17_EXTENSION_COMPILE_OPTION "-std=gnu++1z")
 endif()
 
+if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 8.0)
+  set(CMAKE_CXX20_STANDARD_COMPILE_OPTION "-std=c++2a")
+  set(CMAKE_CXX20_EXTENSION_COMPILE_OPTION "-std=gnu++2a")
+endif()
+
 __compiler_check_default_language_standard(CXX 3.4 98 6.0 14)
diff --git a/Modules/Compiler/MSVC-C-FeatureTests.cmake b/Modules/Compiler/MSVC-C-FeatureTests.cmake
new file mode 100644
index 0000000..3f09be2
--- /dev/null
+++ b/Modules/Compiler/MSVC-C-FeatureTests.cmake
@@ -0,0 +1,8 @@
+set(_cmake_oldestSupported "_MSC_VER >= 1600")
+
+# Not yet supported:
+#set(_cmake_feature_test_c_static_assert "")
+#set(_cmake_feature_test_c_restrict "")
+
+set(_cmake_feature_test_c_variadic_macros "${_cmake_oldestSupported}")
+set(_cmake_feature_test_c_function_prototypes "${_cmake_oldestSupported}")
diff --git a/Modules/Compiler/MSVC-C.cmake b/Modules/Compiler/MSVC-C.cmake
new file mode 100644
index 0000000..22c34f8
--- /dev/null
+++ b/Modules/Compiler/MSVC-C.cmake
@@ -0,0 +1,25 @@
+# MSVC has no specific options to set C language standards, but set them as
+# empty strings anyways so the feature test infrastructure can at least check
+# to see if they are defined.
+set(CMAKE_C90_STANDARD_COMPILE_OPTION "")
+set(CMAKE_C90_EXTENSION_COMPILE_OPTION "")
+set(CMAKE_C99_STANDARD_COMPILE_OPTION "")
+set(CMAKE_C99_EXTENSION_COMPILE_OPTION "")
+set(CMAKE_C11_STANDARD_COMPILE_OPTION "")
+set(CMAKE_C11_EXTENSION_COMPILE_OPTION "")
+
+# There is no meaningful default for this
+set(CMAKE_C_STANDARD_DEFAULT "")
+
+# There are no C compiler modes so we only need to test features once.
+# Override the default macro for this special case.  Pretend that
+# all language standards are available so that at least compilation
+# can be attempted.
+macro(cmake_record_c_compile_features)
+  list(APPEND CMAKE_C_COMPILE_FEATURES
+    c_std_90
+    c_std_99
+    c_std_11
+    )
+  _record_compiler_features(C "" CMAKE_C_COMPILE_FEATURES)
+endmacro()
diff --git a/Modules/Compiler/MSVC-CXX.cmake b/Modules/Compiler/MSVC-CXX.cmake
index 789fff5..be259ff 100644
--- a/Modules/Compiler/MSVC-CXX.cmake
+++ b/Modules/Compiler/MSVC-CXX.cmake
@@ -22,6 +22,10 @@ if ((CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 19.0.24215.1 AND
     set(CMAKE_CXX17_STANDARD_COMPILE_OPTION "-std:c++latest")
     set(CMAKE_CXX17_EXTENSION_COMPILE_OPTION "-std:c++latest")
   endif()
+  if (CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 19.12.25835)
+    set(CMAKE_CXX20_STANDARD_COMPILE_OPTION "-std:c++latest")
+    set(CMAKE_CXX20_EXTENSION_COMPILE_OPTION "-std:c++latest")
+  endif()
 
   __compiler_check_default_language_standard(CXX 19.0 14)
 
@@ -29,6 +33,12 @@ if ((CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 19.0.24215.1 AND
   # for meta-features for C++14 and above.  Override the default macro
   # to avoid doing unnecessary work.
   macro(cmake_record_cxx_compile_features)
+    if (DEFINED CMAKE_CXX20_STANDARD_COMPILE_OPTION)
+      list(APPEND CMAKE_CXX20_COMPILE_FEATURES cxx_std_20)
+    endif()
+    # The main cmake_record_cxx_compile_features macro makes all
+    # these conditional on CMAKE_CXX##_STANDARD_COMPILE_OPTION,
+    # but we can skip the conditions because we set them above.
     list(APPEND CMAKE_CXX17_COMPILE_FEATURES cxx_std_17)
     list(APPEND CMAKE_CXX14_COMPILE_FEATURES cxx_std_14)
     list(APPEND CMAKE_CXX98_COMPILE_FEATURES cxx_std_11) # no flag needed for 11
@@ -46,6 +56,8 @@ elseif (CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 16.0)
   set(CMAKE_CXX14_EXTENSION_COMPILE_OPTION "")
   set(CMAKE_CXX17_STANDARD_COMPILE_OPTION "")
   set(CMAKE_CXX17_EXTENSION_COMPILE_OPTION "")
+  set(CMAKE_CXX20_STANDARD_COMPILE_OPTION "")
+  set(CMAKE_CXX20_EXTENSION_COMPILE_OPTION "")
 
   # There is no meaningful default for this
   set(CMAKE_CXX_STANDARD_DEFAULT "")
@@ -60,6 +72,7 @@ elseif (CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 16.0)
       cxx_std_11
       cxx_std_14
       cxx_std_17
+      cxx_std_20
       )
     _record_compiler_features(CXX "" CMAKE_CXX_COMPILE_FEATURES)
   endmacro()
diff --git a/Modules/Compiler/NVIDIA-DetermineCompiler.cmake b/Modules/Compiler/NVIDIA-DetermineCompiler.cmake
index cb0beaf..bf9111a 100644
--- a/Modules/Compiler/NVIDIA-DetermineCompiler.cmake
+++ b/Modules/Compiler/NVIDIA-DetermineCompiler.cmake
@@ -2,9 +2,11 @@
 set(_compiler_id_pp_test "defined(__NVCC__)")
 
 set(_compiler_id_version_compute "
-# define @PREFIX@COMPILER_VERSION_MAJOR @MACRO_DEC@(__CUDACC_VER_MAJOR__)
-# define @PREFIX@COMPILER_VERSION_MINOR @MACRO_DEC@(__CUDACC_VER_MINOR__)
-# define @PREFIX@COMPILER_VERSION_PATCH @MACRO_DEC@(__CUDACC_VER_BUILD__)
+# if defined(__CUDACC_VER_MAJOR__)
+#  define @PREFIX@COMPILER_VERSION_MAJOR @MACRO_DEC@(__CUDACC_VER_MAJOR__)
+#  define @PREFIX@COMPILER_VERSION_MINOR @MACRO_DEC@(__CUDACC_VER_MINOR__)
+#  define @PREFIX@COMPILER_VERSION_PATCH @MACRO_DEC@(__CUDACC_VER_BUILD__)
+# endif
 # if defined(_MSC_VER)
    /* _MSC_VER = VVRR */
 #  define @PREFIX@SIMULATE_VERSION_MAJOR @MACRO_DEC@(_MSC_VER / 100)
diff --git a/Modules/Compiler/SunPro-C.cmake b/Modules/Compiler/SunPro-C.cmake
index 29c2f22..8d0e6d6 100644
--- a/Modules/Compiler/SunPro-C.cmake
+++ b/Modules/Compiler/SunPro-C.cmake
@@ -18,6 +18,8 @@ string(APPEND CMAKE_C_FLAGS_MINSIZEREL_INIT " -xO2 -xspace -DNDEBUG")
 string(APPEND CMAKE_C_FLAGS_RELEASE_INIT " -xO3 -DNDEBUG")
 string(APPEND CMAKE_C_FLAGS_RELWITHDEBINFO_INIT " -g -xO2 -DNDEBUG")
 
+set(CMAKE_DEPFILE_FLAGS_C "-xMD -xMF <DEPFILE>")
+
 # Initialize C link type selection flags.  These flags are used when
 # building a shared library, shared module, or executable that links
 # to other libraries to select whether to use the static or shared
diff --git a/Modules/Compiler/SunPro-CXX.cmake b/Modules/Compiler/SunPro-CXX.cmake
index 5cb7edc..14196b7 100644
--- a/Modules/Compiler/SunPro-CXX.cmake
+++ b/Modules/Compiler/SunPro-CXX.cmake
@@ -18,6 +18,8 @@ string(APPEND CMAKE_CXX_FLAGS_MINSIZEREL_INIT " -xO2 -xspace -DNDEBUG")
 string(APPEND CMAKE_CXX_FLAGS_RELEASE_INIT " -xO3 -DNDEBUG")
 string(APPEND CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT " -g -xO2 -DNDEBUG")
 
+set(CMAKE_DEPFILE_FLAGS_CXX "-xMD -xMF <DEPFILE>")
+
 # Initialize C link type selection flags.  These flags are used when
 # building a shared library, shared module, or executable that links
 # to other libraries to select whether to use the static or shared
diff --git a/Modules/Compiler/XL.cmake b/Modules/Compiler/XL.cmake
index e527a04..3361f8f 100644
--- a/Modules/Compiler/XL.cmake
+++ b/Modules/Compiler/XL.cmake
@@ -30,6 +30,8 @@ macro(__compiler_xl lang)
   set(CMAKE_${lang}_CREATE_PREPROCESSED_SOURCE "<CMAKE_${lang}_COMPILER> <DEFINES> <INCLUDES> <FLAGS> -E <SOURCE> > <PREPROCESSED_SOURCE>")
   set(CMAKE_${lang}_CREATE_ASSEMBLY_SOURCE     "<CMAKE_${lang}_COMPILER> <DEFINES> <INCLUDES> <FLAGS> -S <SOURCE> -o <ASSEMBLY_SOURCE>")
 
+  set(CMAKE_DEPFILE_FLAGS_${lang} "-MF <DEPFILE> -qmakedep=gcc")
+
   # CMAKE_XL_CreateExportList is part of the AIX XL compilers but not the linux ones.
   # If we found the tool, we'll use it to create exports, otherwise stick with the regular
   # create shared library compile line.