+
+ # Check if -Wnon-virtual-dtor warns even though the class is marked final.
+ # If it does, don't add it. So it won't be added on clang 3.4 and older.
+ # This also catches cases when -Wnon-virtual-dtor isn't supported by
+ # the compiler at all.
+ set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
+ set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -std=c++11 -Werror=non-virtual-dtor")
+ CHECK_CXX_SOURCE_COMPILES("class base {public: virtual void anchor();protected: ~base();};
+ class derived final : public base { public: ~derived();};
+ int main() { return 0; }"
+ CXX_WONT_WARN_ON_FINAL_NONVIRTUALDTOR)
+ set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
+ append_if(CXX_WONT_WARN_ON_FINAL_NONVIRTUALDTOR
+ "-Wnon-virtual-dtor" CMAKE_CXX_FLAGS)
+
+ # Check if -Wcomment is OK with an // comment ending with '\' if the next
+ # line is also a // comment.
+ set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
+ set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -Werror -Wcomment")
+ CHECK_C_SOURCE_COMPILES("// \\\\\\n//\\nint main() {return 0;}"
+ C_WCOMMENT_ALLOWS_LINE_WRAP)
+ set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
+ if (NOT C_WCOMMENT_ALLOWS_LINE_WRAP)
+ append("-Wno-comment" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+ endif()