One year passed from the time when the last major version of the GNU Compiler Collection has been announced, so it is the time again to announce a new major GCC release, 5.1.
GCC 5.1 is a major release containing substantial new functionality not available in GCC 4.9.x or previous GCC releases.
The C++ front-end now has full C++14 language support and the Standard C++ Library has full C++11 support and experimental full C++14 support. The full C++11 support has been made possible by adopting Dual ABI.
The C front-end now defaults to C11 mode with GNU extensions, which affects semantics of the inline keyword and brings several other user visible changes.
— From a GCC Announce Newsletter