Before you do anything else, you should read the file FAQ located at the top level of the source tree. This file answers common questions and describes problems you may experience with compilation and installation. It is updated more frequently than this manual.
Features can be added to GNU Libc via add-on bundles. These are
separate tar files, which you unpack into the top level of the source
tree. Then you give configure the ‘--enable-add-ons’ option
to activate them, and they will be compiled into the library.
You will need recent versions of several GNU tools: definitely GCC and GNU Make, and possibly others. See Tools for Compilation, below.