Index: cmake/modules/HandleLLVMOptions.cmake
===================================================================
--- cmake/modules/HandleLLVMOptions.cmake
+++ cmake/modules/HandleLLVMOptions.cmake
@@ -555,7 +555,7 @@
     append("-Wall" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
   endif()
 
-  append("-W -Wno-unused-parameter -Wwrite-strings" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+  append("-Wextra -Wno-unused-parameter -Wwrite-strings" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
   append("-Wcast-qual" CMAKE_CXX_FLAGS)
 
   # Turn off missing field initializer warnings for gcc to avoid noise from