GCC 6.1 is a major release containing substantial new functionality not available in GCC 5.x or previous GCC releases.
The C++ frontend now defaults to C++14 standard instead of C++98 it has been defaulting to previously. <…> The experimental C++17 support has been enhanced in this release.
This releases features various improvements in the emitted diagnostics, including improved locations, location ranges, suggestions for misspelled identifiers, option names etc., fix-it hints and a couple of new warnings have been added.
— From a GCC Announce Newsletter