As of Fedora 19, GCC 4.8.x is shipped as the default GCC. In addition, all Fedora packages have been rebuilt with GCC 4.8.x (and GLIBC 2.17; see below)
Users will be able to see compiled code improvements and use the newly added features, such as improved C++11 and C11 support, improved vectorization support, etc.
For more information on the changes in GCC 4.8.x, please see http://gcc.gnu.org/gcc-4.8/changes.html
As of Fedora 19, GLIBC 2.17 is shipped as the default GLIBC. All Fedora packages have been rebuilt with GLIBC 2.17 (and GCC 4.8.x; see above).
For more information on the changes in GLIBC 2.17, please see http://sourceware.org/ml/libc-announce/2012/msg00001.html