MongoDB in its code use hexadecimal floats. MongoDB requires c++11 support, but it enables it by -std=c++11 compiler flag.

It should be used -std=gnu++11 instead of it. Hexadecimal floats are not part of c++11 and are only in extensions. It was working but with latest version of gcc 6.0 it is failing.

See https://bugzilla.redhat.com/show_bug.cgi?id=1321986