## Test Without installing the new software that you just build (because that could override the existing and working version), test that it works.{Admon/important|Read the glibc Instructions|The glibc software and build system are complex, since this is core library which underlies most of the software on the system. [https://www.gnu.org/software/libc/ Read the documentation carefully.]}# Build and test glibc## Find and build the source code for the latest released version of the GNU Standard C Library (glibc). Note that glibc uses two parallel directory trees: one which contains the source code, and one which contains configuration and the output of the build system. You can safely delete all of the contents of the build directory and rebuild at any time.## Test the library which you have built (Critical: do this without installing it on your system and overwriting your existing glibc installation!). Prove that your version of the library is used in your testsby introducing a change in behaviour (for example, a small bug).## There may be multiple implementations of a function.