Index: /trunk/Mars/CMakeLists.txt
===================================================================
--- /trunk/Mars/CMakeLists.txt	(revision 19789)
+++ /trunk/Mars/CMakeLists.txt	(revision 19790)
@@ -2,7 +2,9 @@
 # ************ cmake **************
 # *********************************
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0 FATAL_ERROR)
+CMAKE_MINIMUM_REQUIRED(VERSION 3.1 FATAL_ERROR)
 CMAKE_POLICY(SET CMP0043 NEW)
 CMAKE_POLICY(SET CMP0048 NEW)
+
+# TARGET_SOURCES requires v3.1
 
 # Enable debug symbols by default
@@ -48,7 +50,7 @@
     ENDIF()
 ELSEIF ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
-    SET(CLANG_MIN 3.8)
-    IF (CMAKE_C_COMPILER_VERSION VERSION_LESS 3.8 OR
-        CMAKE_CXX_COMPILER_VERSION VERSION_LESS 3.8)
+    SET(CLANG_MIN 3.5)
+    IF (CMAKE_C_COMPILER_VERSION VERSION_LESS CLANG_MIN OR
+        CMAKE_CXX_COMPILER_VERSION VERSION_LESS CLANG_MIN)
         MESSAGE(FATAL_ERROR "\n  clang/clang++ ${CLANG_MIN} or higher is required.\n  You are running version ${CMAKE_C_COMPILER_VERSION}/${CMAKE_CXX_COMPILER_VERSION}.")
     ENDIF()
@@ -235,5 +237,5 @@
 #      ^~~~~~~~~~~~~~~
 
-IF(ROOT_VERSION VERSION_GREATER_EQUAL 6.18 AND ROOT_VERSION VERSION_LESS 6.19)
+IF(NOT ROOT_VERSION VERSION_LESS 6.18 AND ROOT_VERSION VERSION_LESS 6.19)
    SET(CMAKE_CXX_FLAGS
        "${CMAKE_CXX_FLAGS} -Wno-cast-align")