Errors for sign-compare, since gcc6 is stricter

Author: cdunn2001

CMakeLists.txt

@@ -103,7 +103,7 @@ endif()
 
 if (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
   # using regular Clang or AppleClang
-  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -Wall -Wconversion -Wshadow -Wno-sign-conversion -Werror=conversion")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -Wall -Wconversion -Wshadow -Wno-sign-conversion -Werror=conversion -Werror=sign-compare")
 elseif (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
   # using GCC
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -Wall -Wconversion -Wshadow -Wextra -Werror=conversion")