Project: Determine default language dialect for the compiler.

Use the __cplusplus and __STDC_VERSION__ macros to automatically
determine the default dialect for the compiler while determining its
id and version.

7 files changed, 34 insertions, 15 deletions

diff --git a/Modules/Compiler/AppleClang-C.cmake b/Modules/Compiler/AppleClang-C.cmake
index 10454f6..1db7d9e 100644
--- a/Modules/Compiler/AppleClang-C.cmake
+++ b/Modules/Compiler/AppleClang-C.cmake
@@ -13,7 +13,10 @@ if(NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 4.0)
 endif()
 
 if(NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 4.0)
-  set(CMAKE_C_STANDARD_DEFAULT 99)
+  if (NOT CMAKE_C_STANDARD_COMPUTED_DEFAULT)
+    message(FATAL_ERROR "CMAKE_C_STANDARD_COMPUTED_DEFAULT should be set for ${CMAKE_C_COMPILER_ID} (${CMAKE_C_COMPILER}) version ${CMAKE_C_COMPILER_VERSION}")
+  endif()
+  set(CMAKE_C_STANDARD_DEFAULT ${CMAKE_C_STANDARD_COMPUTED_DEFAULT})
 endif()
 
 macro(cmake_record_c_compile_features)
diff --git a/Modules/Compiler/AppleClang-CXX.cmake b/Modules/Compiler/AppleClang-CXX.cmake
index 1ba8a77..031851a 100644
--- a/Modules/Compiler/AppleClang-CXX.cmake
+++ b/Modules/Compiler/AppleClang-CXX.cmake
@@ -23,9 +23,13 @@ elseif(NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 5.1)
 endif()
 
 if(NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.0)
-  set(CMAKE_CXX_STANDARD_DEFAULT 98)
+  if (NOT CMAKE_CXX_STANDARD_COMPUTED_DEFAULT)
+    message(FATAL_ERROR "CMAKE_CXX_STANDARD_COMPUTED_DEFAULT should be set for ${CMAKE_CXX_COMPILER_ID} (${CMAKE_CXX_COMPILER}) version ${CMAKE_CXX_COMPILER_VERSION}")
+  endif()
+  set(CMAKE_CXX_STANDARD_DEFAULT ${CMAKE_CXX_STANDARD_COMPUTED_DEFAULT})
 endif()
 
+
 macro(cmake_record_cxx_compile_features)
   macro(_get_appleclang_features std_version list)
     record_compiler_features(CXX "${std_version}" ${list})
diff --git a/Modules/Compiler/Clang-C.cmake b/Modules/Compiler/Clang-C.cmake
index 548d0a5..ef3a46a 100644
--- a/Modules/Compiler/Clang-C.cmake
+++ b/Modules/Compiler/Clang-C.cmake
@@ -17,10 +17,11 @@ if(NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 3.4)
   set(CMAKE_C11_EXTENSION_COMPILE_OPTION "-std=gnu11")
 endif()
 
-if(NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 3.6)
-  set(CMAKE_C_STANDARD_DEFAULT 11)
-elseif(NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 3.4)
-  set(CMAKE_C_STANDARD_DEFAULT 99)
+if(NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 3.4)
+  if (NOT CMAKE_C_STANDARD_COMPUTED_DEFAULT)
+    message(FATAL_ERROR "CMAKE_C_STANDARD_COMPUTED_DEFAULT should be set for ${CMAKE_C_COMPILER_ID} (${CMAKE_C_COMPILER}) version ${CMAKE_C_COMPILER_VERSION}")
+  endif()
+  set(CMAKE_C_STANDARD_DEFAULT ${CMAKE_C_STANDARD_COMPUTED_DEFAULT})
 endif()
 
 macro(cmake_record_c_compile_features)
diff --git a/Modules/Compiler/Clang-CXX.cmake b/Modules/Compiler/Clang-CXX.cmake
index 84b2c74..fcc7319 100644
--- a/Modules/Compiler/Clang-CXX.cmake
+++ b/Modules/Compiler/Clang-CXX.cmake
@@ -31,8 +31,11 @@ elseif(NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 3.4)
   set(CMAKE_CXX14_EXTENSION_COMPILE_OPTION "-std=gnu++1y")
 endif()
 
-if(UNIX AND NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 3.4)
-  set(CMAKE_CXX_STANDARD_DEFAULT 98)
+if(NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 3.4)
+  if (NOT CMAKE_CXX_STANDARD_COMPUTED_DEFAULT)
+    message(FATAL_ERROR "CMAKE_CXX_STANDARD_COMPUTED_DEFAULT should be set for ${CMAKE_CXX_COMPILER_ID} (${CMAKE_CXX_COMPILER}) version ${CMAKE_CXX_COMPILER_VERSION}")
+  endif()
+  set(CMAKE_CXX_STANDARD_DEFAULT ${CMAKE_CXX_STANDARD_COMPUTED_DEFAULT})
 endif()
 
 macro(cmake_record_cxx_compile_features)
diff --git a/Modules/Compiler/GNU-C.cmake b/Modules/Compiler/GNU-C.cmake
index 031ab73..5c68b1e 100644
--- a/Modules/Compiler/GNU-C.cmake
+++ b/Modules/Compiler/GNU-C.cmake
@@ -22,12 +22,14 @@ elseif (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 4.6)
   set(CMAKE_C11_EXTENSION_COMPILE_OPTION "-std=gnu1x")
 endif()
 
-if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 5.0)
-  set(CMAKE_C_STANDARD_DEFAULT 11)
-elseif(NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 4.4)
-  set(CMAKE_C_STANDARD_DEFAULT 90)
+if(NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 4.4)
+  if (NOT CMAKE_C_STANDARD_COMPUTED_DEFAULT)
+    message(FATAL_ERROR "CMAKE_C_STANDARD_COMPUTED_DEFAULT should be set for ${CMAKE_C_COMPILER_ID} (${CMAKE_C_COMPILER}) version ${CMAKE_C_COMPILER_VERSION}")
+  endif()
+  set(CMAKE_C_STANDARD_DEFAULT ${CMAKE_C_STANDARD_COMPUTED_DEFAULT})
 endif()
 
+
 macro(cmake_record_c_compile_features)
   macro(_get_gcc_features std_version list)
     record_compiler_features(C "${std_version}" ${list})
diff --git a/Modules/Compiler/GNU-CXX.cmake b/Modules/Compiler/GNU-CXX.cmake
index 2dc02f0..cbb0293 100644
--- a/Modules/Compiler/GNU-CXX.cmake
+++ b/Modules/Compiler/GNU-CXX.cmake
@@ -35,7 +35,10 @@ elseif (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.8)
 endif()
 
 if(NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.4)
-  set(CMAKE_CXX_STANDARD_DEFAULT 98)
+  if (NOT CMAKE_CXX_STANDARD_COMPUTED_DEFAULT)
+    message(FATAL_ERROR "CMAKE_CXX_STANDARD_COMPUTED_DEFAULT should be set for ${CMAKE_CXX_COMPILER_ID} (${CMAKE_CXX_COMPILER}) version ${CMAKE_CXX_COMPILER_VERSION}")
+  endif()
+  set(CMAKE_CXX_STANDARD_DEFAULT ${CMAKE_CXX_STANDARD_COMPUTED_DEFAULT})
 endif()
 
 macro(cmake_record_cxx_compile_features)
diff --git a/Modules/Compiler/SunPro-CXX.cmake b/Modules/Compiler/SunPro-CXX.cmake
index e0c02d9..ff68ee9 100644
--- a/Modules/Compiler/SunPro-CXX.cmake
+++ b/Modules/Compiler/SunPro-CXX.cmake
@@ -36,8 +36,11 @@ if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 5.13)
   set(CMAKE_CXX11_EXTENSION_COMPILE_OPTION "-std=c++11")
 endif()
 
-if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 5.13)
-  set(CMAKE_CXX_STANDARD_DEFAULT 98)
+if(NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 5.13)
+  if (NOT CMAKE_CXX_STANDARD_COMPUTED_DEFAULT)
+    message(FATAL_ERROR "CMAKE_CXX_STANDARD_COMPUTED_DEFAULT should be set for ${CMAKE_CXX_COMPILER_ID} (${CMAKE_CXX_COMPILER}) version ${CMAKE_CXX_COMPILER_VERSION}")
+  endif()
+  set(CMAKE_CXX_STANDARD_DEFAULT ${CMAKE_CXX_STANDARD_COMPUTED_DEFAULT})
 endif()
 
 macro(cmake_record_cxx_compile_features)