The GNU C Library provides many of the low-level components used directly by programs written in the C or C++ languages. Many programming languages use the GNU C Library indirectly including C#, Java, Perl, Python, and Ruby (interpreters, VMs, or compiled code for these languages use glibc directly).
In the simplest case the program uses the glibc provided by the distribution, but you aren't limited to this. Perhaps you want to test a new feature, or a developer has asked if you can reproduce the bug with the latest glibc.
Whatever your needs are, these intructions are designed to guide you through the process of building and using upstream glibc.
Releases are available by source branch checkout (gitweb) and tarball via ftp.
Checkout the latest glibc 2.40 stable release:
git clone https://sourceware.org/git/glibc.git
cd glibc
git checkout release/2.40/master
Release tarballs are available via anonymous ftp at https://ftp.gnu.org/gnu/glibc/ and its mirrors.
Build and test the libraries following instructions here.
The #glibc channel is registered on irc.oftc.net along with other GNU Toolchain projects including gcc on #gcc. Please feel free to join the channel and ask any questions.
The glibc mailing lists are hosted on sourceware.org:
libc-announce: The libc-anounce list is used to inform users and developers of upcoming releases and anouncements.
libc-help: The libc-help list is intended for all glibc questions including build problems, C library usage, and more. No question about glibc is ever wrong on this list.
For more mailing lists see Getting involved.