CMake: Emit error for old incompatible compilers

diff --git a/cmake/setup_compiler_flags_gnu.cmake b/cmake/setup_compiler_flags_gnu.cmake
index 28b00ed5b3e3d743a38aa5a918ff3e20f78f10d6..a14a4b97174edfa10bd8eb1a3cd9763f17b4fe09 100644 (file)
--- a/cmake/setup_compiler_flags_gnu.cmake
+++ b/cmake/setup_compiler_flags_gnu.cmake
@@ -22,7 +22,7 @@
 
 IF( CMAKE_CXX_COMPILER_ID MATCHES "GNU" AND
     CMAKE_CXX_COMPILER_VERSION VERSION_LESS "4.9" )
-  MESSAGE(WARNING "\n"
+  MESSAGE(FATAL_ERROR "\n"
     "deal.II requires support for features of C++14 that are not present in\n"
     "versions of GCC prior to 4.9."
     )
@@ -30,7 +30,7 @@ ENDIF()
 
 IF( CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND
     CMAKE_CXX_COMPILER_VERSION VERSION_LESS "4.0" )
-  MESSAGE(WARNING "\n"
+  MESSAGE(FATAL_ERROR "\n"
     "deal.II requires support for features of C++14 that are not present in\n"
     "versions of Clang prior to 4.0."
     )
@@ -41,7 +41,7 @@ ENDIF()
 IF (POLICY CMP0025)
   IF( CMAKE_CXX_COMPILER_ID MATCHES "AppleClang" AND
       CMAKE_CXX_COMPILER_VERSION VERSION_LESS "9.0" )
-    MESSAGE(WARNING "\n"
+    MESSAGE(FATAL_ERROR "\n"
       "deal.II requires support for features of C++14 that are not present in\n"
       "versions of AppleClang prior to 9.0."
       )