From Fedora Project Wiki
GCC 5.1.1
Fedora 23 is built on GCC 5.1.1. For information on building your own code with this compiler release, refer to the upstream change info at https://gcc.gnu.org/gcc-5/changes.html
glibc 2.22
Fedora 23 provides version 2.22 of the GNU C libraries. Learn about the changes available in the latest version of glibc from the project's release announcement at https://www.sourceware.org/ml/libc-alpha/2015-08/msg00609.html