Table of contents:
1) Dependencies for using gnulib-tool (maintainer environment)
2) Dependencies for building the imported code (target environment)


1) Dependencies for using gnulib-tool (maintainer environment)
**************************************************************

The following packages are needed by maintainers for using 'gnulib-tool'.
We call this the "maintainer environment", although it is not necessarily
a maintainer's or developer's machine; it can also be some containerized
environment.

In general, Gnulib prefers the latest stable version of each package,
but in some cases it also supports older versions; this caters to
commonly-used software distributions that may lag behind the latest
stable package. Support for older versions is not guaranteed, though,
and the version numbers in the following list may be incremented
at any time.

* A C runtime, compiler, linker, etc.
  + Mandatory. Using the platform's native 'cc' gives good portability
    exposure, but you can also use GCC 3.1 or newer.
  + GCC Homepage:
    https://gcc.gnu.org/
  + Download:
    https://ftp.gnu.org/gnu/gcc/

* A 'make' utility.
  + Mandatory. Using the platform's native 'make' gives good portability
    exposure for in-tree builds, but VPATH builds on OpenBSD or Solaris
    require GNU Make 3.79.1 or newer.
  + GNU Make Homepage:
    https://www.gnu.org/software/make/
  + Download:
    https://ftp.gnu.org/gnu/make/

* GNU M4 1.4.5 or newer.
  + Mandatory.
    1.4.5 or newer is mandatory, but 1.4.9 or newer is recommended.
    If you want to build it from source, use the tarball from
    https://gitlab.com/gnu-m4/ci-distcheck/-/jobs/artifacts/master/raw/m4-snapshot.tar?job=check-optimized
  + Homepage:
    https://www.gnu.org/software/m4/
  + Download:
    https://ftp.gnu.org/gnu/m4/

* Autoconf 2.64 or newer.
  + Mandatory.
  + Homepage:
    https://www.gnu.org/software/autoconf/
  + Download:
    https://ftp.gnu.org/gnu/autoconf/

* Automake 1.14 or newer.
  + Mandatory.
  + Homepage:
    https://www.gnu.org/software/automake/
  + Download:
    https://ftp.gnu.org/gnu/automake/

* A shell
  + Mandatory. Using the platform's native 'sh' gives good portability
    exposure, but you can also use Bash.
  + Homepage:
    https://www.gnu.org/software/bash/
  + Download:
    https://ftp.gnu.org/gnu/bash/

* Core POSIX utilities, including:
    [ basename cat chgrp chmod chown cp dd echo expand expr
    false hostname install join kill ln ls md5sum mkdir mkfifo
    mknod mv printenv pwd rm rmdir sleep sort tee test touch
    true uname
  + Mandatory. Using the platform's native utilities gives good portability
    exposure, but you can also use GNU coreutils.
  + Homepage:
    https://www.gnu.org/software/coreutils/
  + Download:
    https://ftp.gnu.org/gnu/coreutils/

* The comparison utilities 'cmp' and 'diff'.
  + Mandatory. Using the platform's native utilities gives good portability
    exposure, but you can also use GNU diffutils.
  + Homepage:
    https://www.gnu.org/software/diffutils/
  + Download:
    https://ftp.gnu.org/gnu/diffutils/

* The patch utility 'patch'.
  + Mandatory if you use gnulib-local diffs. Using the platform's native
    utilities gives good portability exposure, but you can also use GNU
    patch.
  + Homepage:
    https://www.gnu.org/software/patch/
  + Download:
    https://ftp.gnu.org/gnu/patch/

* Grep.
  + Mandatory. Using the platform's native grep gives good portability
    exposure, but you can also use GNU grep.
  + Homepage:
    https://www.gnu.org/software/grep/
  + Download:
    https://ftp.gnu.org/gnu/grep/

* Awk.
  + Mandatory.
    Using the platform's native awk, mawk, or nawk gives good portability
    exposure, but you can also use GNU awk.
  + Homepage:
    https://www.gnu.org/software/gawk/
  + Download:
    https://ftp.gnu.org/gnu/gawk/

* Python 3.7 or newer.
  * Recommended.
    Without it, gnulib-tool is between 8 times and 100 times slower and may lack
    functionality added after April 2024.
  + Homepage:
    https://www.python.org/
  + Download:
    https://www.python.org/downloads/
  + Pre-built package name:
    - On Debian and Debian-based systems: python3,
    - On Red Hat distributions: python3.
    - Other: https://repology.org/project/python/versions

* GNU gettext.
  + If your project wants to follow GNU Coding Standards:
    + Always use the newest available gettext release, see
      <https://www.gnu.org/software/gnulib/manual/html_node/gettextize-and-autopoint.html>.
    + Use the 'gettext' module.
  + If your project cares more about ease of development on older platforms:
    + gettext 0.17 or newer.
    + Use the 'gettext-h' module.
  + Recommended.
    Needed if you use modules that use internationalization (many do).
  + Homepage:
    https://www.gnu.org/software/gettext/
  + Download:
    https://ftp.gnu.org/gnu/gettext/
  + Pre-built package name:
    - On Debian and Debian-based systems: gettext,
    - On Red Hat distributions: gettext.
    - Other: https://repology.org/project/gettext/versions

* Bison 2.0 or newer.
  + Recommended.
    Needed if you use the 'parse-datetime' module.
  + Homepage:
    https://www.gnu.org/software/bison/
  + Download:
    https://ftp.gnu.org/gnu/bison/
  + Pre-built package name:
    - On Debian and Debian-based systems: bison,
    - On Red Hat distributions: bison.
    - Other: https://repology.org/project/bison/versions

* GNU gperf 3.0.1 or newer.
  + 3.0.1 or newer is mandatory, but 3.1 or newer is recommended.
    Needed if you use the 'iconv_open' module or some of the
    unictype/*, unicase/*, uninorm/* modules.
  + Homepage:
    https://www.gnu.org/software/gperf/
  + Download:
    https://ftp.gnu.org/gnu/gperf/
  + Pre-built package name:
    - On Debian and Debian-based systems: gperf,
    - On Red Hat distributions: gperf.
    - Other: https://repology.org/project/gperf/versions

* Texinfo 4.6 or newer.
  + Recommended.
    Needed if you use modules that include documentation.
  + Homepage:
    https://www.gnu.org/software/texinfo/
  + Download:
    https://ftp.gnu.org/gnu/texinfo/
  + Pre-built package name:
    - On Debian and Debian-based systems: texinfo,
    - On Red Hat distributions: texinfo.
    - Other: https://repology.org/project/texinfo/versions

* GNU sed.
  + Recommended.
    Needed on platforms where the vendor's 'sed' program is too buggy.
  + Homepage:
    https://www.gnu.org/software/sed/
  + Download:
    https://ftp.gnu.org/gnu/sed/

* GNU libtool 1.5.22 or newer.
  + Optional.
    Needed if you want to invoke gnulib-tool with option --libtool.
    libtool 2.2.x or newer is needed if you want to invoke gnulib-tool
    with options --create-testdir/--test  and --libtool.
  + Homepage:
    https://www.gnu.org/software/libtool/
  + Download:
    https://ftp.gnu.org/gnu/libtool/

* GNU tar 1.28 or newer.
  + Optional.
    Needed if you use the 'gnumakefile' module, which sets TAR_OPTIONS
    to --sort=names (added in version 1.28) in GNUmakefile for 'make dist'.
  + Homepage:
    https://www.gnu.org/software/tar/
  + Download:
    https://ftp.gnu.org/gnu/tar/

Note: Solaris 10 is no longer supported as maintainer environment.
<https://lists.gnu.org/archive/html/bug-gnulib/2024-07/msg00076.html>


2) Dependencies for building the imported code (target environment)
*******************************************************************

The following packages are needed for building the package that imports
code from Gnulib.

* A C runtime, compiler, linker, etc.
  + Mandatory. Using the platform's native 'cc' gives good portability
    exposure, but you can also use GCC 3.1 or newer.
  + GCC Homepage:
    https://gcc.gnu.org/
  + Download:
    https://ftp.gnu.org/gnu/gcc/

* A 'make' utility.
  + Mandatory. Using the platform's native 'make' gives good portability
    exposure for in-tree builds, but VPATH builds on OpenBSD or Solaris
    require GNU Make 3.79.1 or newer.
  + GNU Make Homepage:
    https://www.gnu.org/software/make/
  + Download:
    https://ftp.gnu.org/gnu/make/

* A shell
  + Mandatory. Using the platform's native 'sh' gives good portability
    exposure, but you can also use Bash.
  + Homepage:
    https://www.gnu.org/software/bash/
  + Download:
    https://ftp.gnu.org/gnu/bash/

* Core POSIX utilities, including:
    [ basename cat chgrp chmod chown cp dd echo expand expr
    false hostname install kill ln ls md5sum mkdir mkfifo
    mknod mv printenv pwd rm rmdir sleep sort tee test touch
    true uname
  + Mandatory. Using the platform's native utilities gives good portability
    exposure, but you can also use GNU coreutils.
  + Homepage:
    https://www.gnu.org/software/coreutils/
  + Download:
    https://ftp.gnu.org/gnu/coreutils/

* The comparison utilities 'cmp' and 'diff'.
  + Mandatory. Using the platform's native utilities gives good portability
    exposure, but you can also use GNU diffutils.
  + Homepage:
    https://www.gnu.org/software/diffutils/
  + Download:
    https://ftp.gnu.org/gnu/diffutils/

* Grep.
  + Mandatory. Using the platform's native grep gives good portability
    exposure, but you can also use GNU grep.
  + Homepage:
    https://www.gnu.org/software/grep/
  + Download:
    https://ftp.gnu.org/gnu/grep/

* Awk.
  + Mandatory.
    Using the platform's native awk, mawk, or nawk gives good portability
    exposure, but you can also use GNU awk.
  + Homepage:
    https://www.gnu.org/software/gawk/
  + Download:
    https://ftp.gnu.org/gnu/gawk/

Prerequisites on Windows
------------------------

* Cygwin
  + Required.
    Provides a POSIX-like environment and binary packages necessary to
    build and run software. Native Windows binaries can be built with
    a packaged mingw tool chain. This method is preferred over MSYS2.
  + Homepage:
    https://cygwin.com/
  + Download:
    https://cygwin.com/install.html

Libraries
---------

Various modules work best with certain libraries installed. These are runtime
dependencies that are also build dependencies.

For modules 'abort-debug' and 'stack-trace':
  * libbacktrace
    + Recommended.
      Needed for producing C stack traces with source file names and
      line numbers.
    + Homepage:
      https://github.com/ianlancetaylor/libbacktrace
    + Download:
      https://github.com/ianlancetaylor/libbacktrace
    + Pre-built package name:
      - On Debian and Debian-based systems: libgcc-N-dev,
      - On Red Hat distributions: --.
      - Other: https://repology.org/project/libbacktrace/versions

For module 'acl':
  * libacl
    + Recommended on Linux systems.
      Needed so that the creation of backup files respects the access control
      lists (ACLs) set on the original files.
    + Homepage:
      https://savannah.nongnu.org/projects/acl/
    + Download:
      https://download.savannah.nongnu.org/releases/acl/
    + Pre-built package name:
      - On Debian and Debian-based systems: libacl1-dev,
      - On Red Hat distributions: libacl-devel.
      - Other: https://repology.org/project/acl/versions
  * libattr
    + Recommended on Linux systems.
      Needed so that the creation of backup files respects the access control
      lists (ACLs) set on the original files, with fewer system calls.
    + Homepage:
      https://savannah.nongnu.org/projects/attr/
    + Download:
      https://download.savannah.nongnu.org/releases/attr/
    + Pre-built package name:
      - On Debian and Debian-based systems: libattr1-dev,
      - On Red Hat distributions: libattr-devel.
      - Other: https://repology.org/project/attr/versions

For module 'gettext-h':
  * libintl, part of GNU gettext
    + Not needed on systems with glibc.
      But highly recommended on all other systems.
      Needed for localization (translation) of messages to the user's
      native language.
    + Homepage:
      https://www.gnu.org/software/gettext/
    + Download:
      https://ftp.gnu.org/gnu/gettext/
    + Pre-built package name:
      - On Debian and Debian-based systems: --,
      - On Red Hat distributions: --.
      - Other: https://repology.org/project/gettext/versions
    + If it is installed in a nonstandard directory, pass the option
      --with-libintl-prefix=DIR to 'configure'.

For module 'iconv':
  * GNU libiconv
    + Not needed on systems with glibc and on NetBSD.
      But highly recommended on all other systems.
      Needed for character set conversion of strings from/to Unicode.
    + Homepage:
      https://www.gnu.org/software/libiconv/
    + Download:
      https://ftp.gnu.org/gnu/libiconv/
    + Pre-built package name:
      - On Debian and Debian-based systems: --,
      - On Red Hat distributions: --.
      - Other: https://repology.org/project/libiconv/versions
    + If it is installed in a nonstandard directory, pass the option
      --with-libiconv-prefix=DIR to 'configure'.
    + On mingw, a slim alternative is the 'win-iconv' package version 0.0.8
      from https://github.com/win-iconv/win-iconv .

For module 'libgmp':
  * GNU gmp.
    + Recommended.
      Needed for fast multiprecision computations.
    + Homepage:
      https://www.gnu.org/software/gmp/
    + Download:
      https://ftp.gnu.org/gnu/gmp/
    + Pre-built package name:
      - On Debian and Debian-based systems: libgmp-dev,
      - On Red Hat distributions: gmp-devel.
      - Other: https://repology.org/project/gmp/versions
    + If it is installed in a nonstandard directory, pass the option
      --with-libgmp-prefix to 'configure'.

For module 'readline':
  * GNU readline
    + Recommended.
      Needed for interactive editing of textual input.
    + Homepage:
      https://www.gnu.org/software/readline/
    + Download:
      https://ftp.gnu.org/gnu/readline/
    + Pre-built package name:
      - On Debian and Debian-based systems: libreadline-dev,
      - On Red Hat distributions: readline-devel.
      - Other: https://repology.org/project/readline/versions
    + If it is installed in a nonstandard directory, pass the option
      --with-libreadline-prefix=DIR to 'configure'.

For modules 'terminfo' and 'termcap':
  * GNU ncurses (preferred)
    or libtermcap (discouraged) or a curses library (legacy).
    + Recommended.
      Needed for fancy input/output in terminal emulators.
    + Homepage:
      https://www.gnu.org/software/ncurses/
    + Download:
      https://ftp.gnu.org/gnu/ncurses/
    + Pre-built package name:
      - On Debian and Debian-based systems: libncurses-dev,
      - On Red Hat distributions: ncurses-devel.
      - Other: https://repology.org/project/ncurses/versions
    + If it is installed in a nonstandard directory, pass the option
      --with-libncurses-prefix=DIR or --with-libtermcap-prefix to 'configure'.

For modules 'crypto/md5-buffer', 'crypto/sha*-buffer':
  * OpenSSL.
    + Optional.
      Needed for optimized crypto hash sums.
    + Homepage:
      https://www.openssl.org/
    + Download:
      https://www.openssl.org/source/
    + Pre-built package name:
      - On Debian and Debian-based systems: libssl-dev,
      - On Red Hat distributions: openssl-devel.
      - Other: https://repology.org/project/openssl/versions

Locales
-------

If your package includes the tests for the Gnulib modules that you imported,
you will want to maximize the test coverage of these tests, that is, to
minimize the number of tests that are skipped. To this effect, you need to
install a couple of locales, used by the tests.

You can get a listing of the locales installed by default through
  $ locale -a
(Note: On glibc systems, this command displays the encoding names in a
mutilated form, e.g. it transforms "en_US.UTF-8" to "en_US.utf8".)

To install the needed locales on glibc systems:

$ sudo localedef -i en_US -f UTF-8 en_US.UTF-8
$ sudo localedef -i ar_SA -f ISO-8859-6 ar_SA.ISO-8859-6
$ sudo localedef -i de_DE -f UTF-8 de_DE.UTF-8
$ sudo localedef -i es_ES -f UTF-8 es_ES.UTF-8
$ sudo localedef -i fa_IR -f UTF-8 fa_IR
$ sudo localedef -i fr_FR -f ISO-8859-1 fr_FR.ISO-8859-1
$ sudo localedef -i fr_FR -f UTF-8 fr_FR.UTF-8
$ sudo localedef -i ja_JP -f EUC-JP ja_JP.EUC-JP
$ sudo localedef -i tr_TR -f UTF-8 tr_TR.UTF-8
$ sudo localedef -i zh_CN -f GB18030 zh_CN.GB18030
$ sudo localedef -i zh_HK -f BIG5-HKSCS zh_HK.BIG5-HKSCS

On Debian and Debian-based systems, if you want these locales to be
persistent across automatic system updates, the approach is different:
There, you need to enable the locales in the file /etc/locale.gen and
then run
$ sudo locale-gen
