Non-type template argument evaluates to -1, which cannot be narrowed to type 'unsigned long long' xcode 4.6

Question

I am using zxing and OpenCV lib in my project. I updated my XCode from 4.5 to 4.6 today and I am getting this error.

externalLibs/boost/include/boost/gil/channel_algorithm.hpp:54:85: Non-type template argument evaluates to -1, which cannot be narrowed to type 'unsigned long long'

And this error is on this line of code in one of the class of OpenCV Library:-

struct unsigned_integral_max_value : public mpl::
integral_c< UnsignedIntegralChannel,-1> {};

On Earlier version of Xcode its working fine.

Thanks in advance.

Answer 1

It seems boost doesn't like c++ 11 support added with the new clang compiler

so.. it say disable c++ 11 support in build settings

= src: see https://svn.boost.org/trac/boost/ticket/7270

Answer 2

The max value of an unsigned long long variable is in hex 0xFFFFFFFF FFFFFFFF, i.e. all bits are 1's. If interpreted as a signed number, this corresponds to a -1. So often programmers use -1 instead, hoping that the compiler will not complain. Apparently, this did not happen in XCode 4.5, but 4.6 does more rigorous checking...

Answer 3

I'm running into the same error when compiling on macOS Sierra with Apple LLVM version 8.1.0 (clang-802.0.42) and -std=c++11. To solve the problem I included the following compiler flag: -Wno-error=c++11-narrowing