What is glibc?
The GNU C Library project provides the core libraries for the GNU system and GNU/Linux systems, as well as many other systems that use Linux as the kernel. These libraries provide critical APIs including ISO C11, POSIX.1-2008, BSD, OS-specific APIs and more. These APIs include such foundational facilities as open, read, write, malloc, printf, getaddrinfo, dlopen, pthread_create, crypt, login, exit and more.
The GNU C Library is designed to be a backwards compatible, portable, and high performance ISO C library. It aims to follow all relevant standards including ISO C11, POSIX.1-2008, and IEEE 754-2008.
The project was started circa 1988 and is almost 30 years old. You can see the complete project release history on the wiki.
The GNU C Library releases every 6 months. See the NEWS file in the glibc sources for more information.
search result on debian8.8 system for libc: libc.find.debian8.txt