Emit warning when AppleClang < 9.0 is detected

diff --git a/cmake/setup_compiler_flags_gnu.cmake b/cmake/setup_compiler_flags_gnu.cmake
index 78a54771d973e3ebfeccd5a2821b1c825cf20495..28b00ed5b3e3d743a38aa5a918ff3e20f78f10d6 100644 (file)
--- a/cmake/setup_compiler_flags_gnu.cmake
+++ b/cmake/setup_compiler_flags_gnu.cmake
@@ -36,6 +36,18 @@ IF( CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND
     )
 ENDIF()
 
+# Correspondence between AppleClang version and upstream Clang version:
+# https://en.wikipedia.org/wiki/Xcode#Xcode_7.0_-_11.x_(since_Free_On-Device_Development)
+IF (POLICY CMP0025)
+  IF( CMAKE_CXX_COMPILER_ID MATCHES "AppleClang" AND
+      CMAKE_CXX_COMPILER_VERSION VERSION_LESS "9.0" )
+    MESSAGE(WARNING "\n"
+      "deal.II requires support for features of C++14 that are not present in\n"
+      "versions of AppleClang prior to 9.0."
+      )
+  ENDIF()
+ENDIF()
+
 
 ########################
 #                      #

diff --git a/doc/readme.html b/doc/readme.html
index 9ee9842e492e874a2c67fbb0766ea9fed7d89609..eecdd24ea195188a2365437c277956838b3ff71d 100644 (file)
--- a/doc/readme.html
+++ b/doc/readme.html
@@ -63,7 +63,8 @@
     </p>
     <ul>
         <li>GNU/Linux: GCC version 4.9 or later; Clang version 4.0 or later; ICC versions 15 or later</li>
-        <li>Mac OS X: GCC version 4.9 or later; Clang version 4.0 or later. Please see the <a href="https://github.com/dealii/dealii/wiki/MacOSX" target="_top">deal.II Wiki</a> for installation instructions.</li>
+        <li>Mac OS X: GCC version 4.9 or later; Clang version 4.0 or later; <a href="https://en.wikipedia.org/wiki/Xcode#Xcode_7.0_-_11.x_(since_Free_On-Device_Development)">Apple Clang version 9.0</a>  or later. 
+            Please see the <a href="https://github.com/dealii/dealii/wiki/MacOSX" target="_top">deal.II Wiki</a> for installation instructions.</li>
         <li>Windows: experimental support for Visual Studio 2017. Please have a look at the
             <a href="https://github.com/dealii/dealii/wiki/Frequently-Asked-Questions#can-i-use-dealii-on-a-windows-platform">
       FAQ</a> and at the <a href="https://github.com/dealii/dealii/wiki/Windows" target="_top">deal.II Wiki</a> for more information and alternative solutions.</li>