This directory is the central repository for Autoconf macros needed to build the teTeX / TeX Live (TL) tree. (1) `Public' macros such as libtool.m4 used to build the libraries and programs in the TL subdirectories libs/*/, utils/*/, and texk/*/ that are owned by the TL tree (i.e., either not maintained independently or with a proxy Makefile.am using an unmodified source tree and bypassing the original build system). Note: the files libtool.m4 and ../build-aux/ltmain.sh must match. (2) `Private' macros for the TL infrastructure, used in directories owned by the TL tree. kpse-pkgs.m4: defines lists of subdirectories libs/LIB/, utils/PROG/, and tex/PROG/ with libraries and programs that can be built as part of the TL tree. kpse-setup.m4: macros that recurse through these lists to provide configure options. They depend on configure fragments */*/ac/withenable.ac defining the dependencies between these libraries and programs. (3) `Public' macros for the TL libraries in the subdirectories libs/*/ and texk/kpathsea/, used to configure programs and other libraries requiring these TL libraries. The macros are designed with the aim that programs maintained independently can be built as part of the TL tree or without TL (using installed versions of the required libraries), ideally using the same unmodified sources.