Features: Populate CMAKE_<LANG>_STANDARD_DEFAULT only for supported compilers.

If no compiler feature information is known for a given compiler
version, do not set a language standard default either.  The two
settings must be recorded consistently.

Modules/Compiler/AppleClang-C.cmake

@@ -12,7 +12,9 @@ if(NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 4.0)
   set(CMAKE_C11_EXTENSION_COMPILE_OPTION "-std=gnu11")
 endif()
 
-set(CMAKE_C_STANDARD_DEFAULT 99)
+if(NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 4.0)
+  set(CMAKE_C_STANDARD_DEFAULT 99)
+endif()
 
 macro(cmake_record_c_compile_features)
   macro(_get_appleclang_features std_version list)

Modules/Compiler/AppleClang-CXX.cmake

@@ -19,7 +19,9 @@ if(NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 5.1)
   set(CMAKE_CXX14_EXTENSION_COMPILE_OPTION "-std=gnu++1y")
 endif()
 
-set(CMAKE_CXX_STANDARD_DEFAULT 98)
+if(NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.0)
+  set(CMAKE_CXX_STANDARD_DEFAULT 98)
+endif()
 
 macro(cmake_record_cxx_compile_features)
   macro(_get_appleclang_features std_version list)

Modules/Compiler/Clang-CXX.cmake

@@ -31,7 +31,9 @@ elseif(NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 3.4)
   set(CMAKE_CXX14_EXTENSION_COMPILE_OPTION "-std=gnu++1y")
 endif()
 
-set(CMAKE_CXX_STANDARD_DEFAULT 98)
+if(UNIX AND NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 3.4)
+  set(CMAKE_CXX_STANDARD_DEFAULT 98)
+endif()
 
 macro(cmake_record_cxx_compile_features)
   macro(_get_clang_features std_version list)

Modules/Compiler/GNU-C.cmake

@@ -24,7 +24,7 @@ endif()
 
 if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 5.0)
   set(CMAKE_C_STANDARD_DEFAULT 11)
-else()
+elseif(NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 4.4)
   set(CMAKE_C_STANDARD_DEFAULT 90)
 endif()
 

Modules/Compiler/GNU-CXX.cmake

@@ -34,7 +34,9 @@ elseif (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.8)
   set(CMAKE_CXX14_EXTENSION_COMPILE_OPTION "-std=gnu++1y")
 endif()
 
-set(CMAKE_CXX_STANDARD_DEFAULT 98)
+if(NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.4)
+  set(CMAKE_CXX_STANDARD_DEFAULT 98)
+endif()
 
 macro(cmake_record_cxx_compile_features)
   macro(_get_gcc_features std_version list)

Modules/Compiler/MSVC-CXX.cmake

@@ -1,5 +1,8 @@
-# MSVC has no specific language level or flags to change it.
-set(CMAKE_CXX_STANDARD_DEFAULT "")
+
+if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 16.0)
+  # MSVC has no specific language level or flags to change it.
+  set(CMAKE_CXX_STANDARD_DEFAULT "")
+endif()
 
 macro(cmake_record_cxx_compile_features)
   record_compiler_features(CXX "" CMAKE_CXX_COMPILE_FEATURES)

Modules/Compiler/SunPro-CXX.cmake

@@ -37,7 +37,9 @@ if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 5.13)
   set(CMAKE_CXX11_EXTENSION_COMPILE_OPTION "-std=c++11")
 endif()
 
-set(CMAKE_CXX_STANDARD_DEFAULT 98)
+if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 5.13)
+  set(CMAKE_CXX_STANDARD_DEFAULT 98)
+endif()
 
 macro(cmake_record_cxx_compile_features)
   macro(_get_solaris_studio_features std_version list)