The warning appears for every line of code in VS2015 (but not clang) that results in a call to fnv1a_hash from hash.hpp.
It appears to be a problem specific to VS2015 with the way the 64 bit fnv1a hash is calculated, but implementing the function mulu64 in the solution by "Cheers and hth. - Alf" in https://stackoverflow.com/questions/37658794/integer-constant-overflow-warning-in-constexpr appears to stop the warning without resorting to setting pragma warnings. Have checked a couple of examples and the hash value generated appears to be the same.
The warning appears for every line of code in VS2015 (but not clang) that results in a call to fnv1a_hash from hash.hpp.
It appears to be a problem specific to VS2015 with the way the 64 bit fnv1a hash is calculated, but implementing the function mulu64 in the solution by "Cheers and hth. - Alf" in https://stackoverflow.com/questions/37658794/integer-constant-overflow-warning-in-constexpr appears to stop the warning without resorting to setting pragma warnings. Have checked a couple of examples and the hash value generated appears to be the same.