Gnulib, the GNU portability library, offers a macro system and C
declarations and definitions for commonly-used API elements and
abstracted system behaviors. It can be used to improve portability and
other functionality in your programs.

Gnulib takes a different approach than libiberty. Gnulib components are
intended to be shared at the source level, rather than being a library that
gets built, installed, and linked against. Thus, there is no distribution
tarball; the idea is to copy files from Gnulib into your own source tree.

However, there are bimonthly stable snapshots of the Gnulib codebase
published at http://erislabs.net/ianb/projects/gnulib/