\input texinfo
@setfilename tlbuild.info

@set version 2023
@set month-year December 2023

@set mytitle Building @TeX{} Live (@value{version})
@settitle @value{mytitle}

@macro TL
@TeX{}@tie{}Live
@end macro

@copying
This file documents the @TL{} build system and more.

@noindent
Copyright @copyright{} 2016--2023 Karl Berry.@*
Copyright @copyright{} 2013--2015 Karl Berry & Peter Breitenlohner.

Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

@ignore
Permission is granted to process this file through TeX and print the
results, provided the printed document carries a copying permission
notice identical to this one except for the removal of this paragraph
(this paragraph not being relevant to the printed manual).
@end ignore

Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the
entire resulting derived work is distributed under the terms of a
permission notice identical to this one.

Permission is granted to copy and distribute translations of this manual
into another language, under the above conditions for modified versions,
except that this permission notice may be stated in a translation
approved by the @TeX{} Users Group.
@end copying

@c Put everything in one index (arbitrarily chosen to be the concept index).
@syncodeindex fn cp
@syncodeindex ky cp
@syncodeindex pg cp
@syncodeindex tp cp
@syncodeindex vr cp

@dircategory TeX
@direntry
* TLbuild: (tlbuild).           TeX Live configuration and development.
@end direntry

@dircategory Individual utilities
@direntry
* install-tl::                  Installing TeX Live.
* tlmgr::                       Managing TeX Live.
@end direntry

@titlepage
@title @value{mytitle}
@subtitle @value{version} release
@subtitle @value{month-year}
@author Peter Breitenlohner
@author Karl Berry
@author @url{https://tug.org/texlive}

@page
@vskip 0pt plus 1filll
@insertcopying
@end titlepage

@shortcontents
@contents

@ifnottex
@node Top
@top @value{mytitle}

For an overview of this manual, @pxref{Introduction}.

@menu
* Introduction::                About this manual.
* Overview of build system::    The @TL{} build system.
* Prerequisites::               Requirements for building @TL{}.
* Building::                    The overall build process.
* Installing::                  How and where installation happens (or not).
* Layout and infrastructure::   Autoconf macros, etc., in detail.
* Configure options::           List of all configure options.
* Coding conventions::          Conventions to follow.
* Continuous integration::      Automated build testing.
* install-tl::                  The @TL{} installer.
* tlmgr::                       The native @TL{} package manager.
* Index::                       General index.
@end menu
@end ifnottex

@node Introduction
@chapter Introduction

@cindex introduction

This manual (dated @value{month-year}) corresponds to the @TL{}
@value{version} release.

This manual is aimed at system installers and programmers, and focuses
on how to configure, build, and develop the @TL{} (TL) sources.  It is
also available as plain text files in the source tree:
@file{source/README.*}.

The main @file{source/README} file in the TL source tree provides
maximally-terse information for doing a build, and portability
information for different systems, along with
@file{source/doc/README.solaris}.

For information on acquiring the TL sources, see
@url{https://tug.org/texlive/svn}.  The canonical source repository
uses Subversion, and we have no plans to change this.

This manual does not duplicate the information found in other TL
documentation resources, such as:

@itemize
@item The @TL{} web pages: @url{https://tug.org/texlive}.

@item The web page describing how to build the binaries which 
are distributed with @TL{}: @url{https://tug.org/texlive/build.html}.

@item The @TL{} user manual: @url{https://tug.org/texlive/doc.html}, or
run @code{texdoc texlive}.

@item Other @TeX{}-related Texinfo manuals (@pxref{,,,web2c, Web2c},
@ref{,,,kpathsea, Kpathsea}, etc.):
@url{https://tug.org/texinfohtml/}, or check the @samp{TeX} category in
the GNU Info system.

@item Package documentation:
@url{https://tug.org/texlive/Contents/live/doc.html}, or the
@file{doc.html} file at the top level of the installed TL.

@end itemize

As an exception, the full documentation for @code{install-tl} and
@code{tlmgr} is included here as appendices, simply because it is easy
to do so.  The same text is available online (linked from
@url{https://tug.org/texlive/doc.html}, or by invoking the program
with @samp{--help} (or look at the end of the source).

@c The first word of the chapter/section title here is used to
@c construct the README.* filenames, so choose well.  (Or hack the script.)

@node Overview of build system
@chapter Overview of build system

@cindex build system, design of

@cindex Autoconf
@cindex Automake
@cindex Libtool
@cindex tests, running
The @TL{} build system was redesigned in 2009 to consistently use
Autoconf, Automake, and Libtool.  Thus, running@*@ @ @ @code{configure
&& make && make check && make install}@*or the essentially-equivalent
top-level @code{Build} script suffices to build and install the TL
programs.  The @code{make check} clause performs various tests of the
generated programs---not strictly required but strongly recommended.
Running @code{configure --help} will display a comprehensive list of
all @code{configure} options.

The main components of the TL build system are:

@table @file
@item libs/@var{lib}
Generic libraries.

@item texk/@var{lib}
@TeX{}-specific libraries in subdirectories, notably
@var{lib}=@code{kpathsea}.  (The other one is @file{texk/ptexenc}.)

@item texk/@var{prog}
@TeX{}-specific programs (that use Kpathsea).

@item utils/@var{prog}
Other programs (that don't use Kpathsea).

@end table

@pindex kpse-pkgs.m4
The primary design goal of the build system is modularity.  Each
program and library module (or package) specifies its own requirements
and properties, such as required libraries, whether an installed
(system) version of a library can be used, @code{configure} options to
be seen at the top level, and more.  An explicit list of all available
modules is kept in a single central place: @file{m4/kpse-pkgs.m4}.

A second, related goal is to configure and build each library before
configuring any other (program or library) module which uses that
library.  This allows checking for properties and features of a
library built as part of the TL tree in much the same way as for a
system version of that library.

All generic libraries and several programs are maintained
independently.  The corresponding modules use (most of) the
distributed source tree and document any modifications of that source.

All this is for the sake of simplifying both upgrading of modules and
integrating new modules into the TL build system.  (Despite all
efforts, neither task is easy.)

@node Prerequisites
@chapter Prerequisites

@cindex prerequisites for building
@cindex requirements for building

@cindex compilers, C and C++11
Overall, building the @TL{} programs, when using all libraries from
the TL source tree, requires C and C++11 compilers, GNU @code{make},
and Python.

@itemize
@item
If @code{make} from your @code{PATH} is not GNU @code{make}, you can
set the @code{MAKE} environment variable to whatever is necessary.

@cindex GNU @code{make}, required
@cindex @code{gmake}, required
@cindex FreeType, requires @code{gmake}
@cindex @code{$@@} target in normal @code{make} rules
GNU @code{make} is required only because of third-party libraries,
notably FreeType.  Automake/Autoconf output in general, and the
TL-maintained directories, work with any reasonable
@code{make}.@footnote{There is one exception in TL: the
@code{tangle-sh} and related rules use @code{$@@} to mean the target
name, a feature not present in all @code{make}s. This could be
alleviated by laborious editing, but since there's no way to avoid GNU
@code{make} for builds of the entire tree, it does not seem worth the
trouble.}

@item
@cindex C++11, required
@cindex @code{dvisvgm}, requires C++11
@cindex HarfBuzz, requires C++11
@cindex ICU, requires C++11
A C++11 compiler is similarly required because of the third-party
libraries ICU and HarfBuzz (at least); the program @code{dvisvgm} also
requires C++11.  It is possible to build what remains with older
compilers, but you have to remove the C++11-dependent sources.
@xref{Build one package}.

@item
@cindex Python, required by ICU
Python is required by ICU tests.  (If you know how to disable these
tests and thus eliminate the requirement, please write.)

@end itemize

A few programs in the tree have additional requirements:

@table @file
@item web2c
@cindex @code{perl}, required by @code{web2c}, etc.
requires @code{perl} for some tests run by @code{make check}.
Incidentally, the @TeX{} Live installer (@code{install-tl}) and
manager (@code{tlmgr}) are also written in Perl, but this does not
matter for compiling the sources.

@item xdvik
@itemx xpdfopen
@cindex X11 development, required by X clients
require X11 headers and libraries, typically in devel(opment) packages
that are not installed by default.

@item xetex
@cindex @code{fontconfig} library, required by @code{xetex}
@cindex @code{ApplicationServices} Mac framework, required by @code{xetex}
@cindex @code{Cocoa} Mac framework, required by @code{xetex}
requires @file{fontconfig} (again both headers and library), or, for
MacOS only, the @code{ApplicationServices} and @code{Cocoa}
frameworks.

@item xindy
@cindex @code{clisp}, required by @code{xindy}
@cindex @code{libsigsegv}, required by @code{xindy}
requires GNU @code{clisp}, @code{libsigsegv}, and @code{libiconv};
additionally, to build the rules and/or documentation: @code{perl},
@code{latex}, @code{pdflatex}.

@end table

@noindent Lacking the required tools, building these
programs must avoided, e.g.,@*
@code{configure --without-x --disable-xetex --disable-xindy}

Modifying source files induces more requirements, as one might expect:

@itemize
@item
Modification of any @code{.y} or @code{.l} source files requires
@file{bison} or @file{flex} to update the corresponding C sources.

@item
Modification of the sources for @code{.info} files requires
@code{makeinfo}.

@item
Modification of any part of the build system (M4 macros,
@file{configure.ac}, @file{Makefile.am}, or their fragments) requires
GNU M4, GNU Autoconf, GNU Automake, and GNU Libtool to update the
generated files.  Furthermore, to reliably reproduce the build files,
the original GNU releases of these tools must be used, not any distro
packaging of them.  @xref{Build system tools}, for more discussion.

@end itemize

If you haven't modified any source files, and infrastructure tools
such as @code{autoconf} or @code{makeinfo} are still being run, check
your timestamps---notably, @code{use-commit-times} must be set to
@code{yes} in your Subversion configuration (@pxref{Build system
tools}).  No infrastructure tools are needed to do a normal build
(barring bugs).

@node Building
@chapter Building

@cindex building
@cindex overall build process

@pindex Build @r{script}
The top-level @file{Build} script is intended to simplify building the
binaries distributed with @TL{} itself---we call this the ``native''
TL build.  It runs @code{configure && make world}, which builds
everything in a subdirectory of the main source tree (default
@file{Work/}), installs everything in another subdirectory (default
@file{inst/}), and finally runs @code{make check}.  The exact
directory and command names can be specified via environment variables
and a few leading options.  All remaining arguments (assignments or
options) are passed to the @file{configure} script.  Please take a
look at the @file{./Build} source file for more information; it is a
straightforward shell script.

@cindex source directory building, not supported
@cindex build directory, required
An alternative, and the one we will mainly discuss here, is to run
@code{configure} and @code{make} in a suitable empty subdirectory.
Building in the source directory itself is not supported (sorry).

@menu
* Build iteration::     What @code{configure} and @code{make} do in TL.
* Build in parallel::   Simultaneous @code{make} processes.
* Build distribution::  Making a distribution tarball.
* Build one package::   Example of working on just one program.
* Build one engine::    Example of building just one @TeX{} engine.
* Cross compilation::   Building on host X for target Y.
@end menu

@node Build iteration
@section Build iteration

@cindex build iteration
@cindex iteration through sources, by @code{configure} and @code{make}

Running the top-level @file{configure} script configures the top level
and the subdirectories @file{libs}, @file{utils}, and @file{texk}.
Running @code{make} at the top level first iterates over the
@TeX{}-specific libraries, and then runs @code{make} in @file{libs},
@file{utils}, and @file{texk} to iterate over the generic libraries,
utility programs, and @TeX{}-specific programs, respectively.  These
iterations consist of two steps:

@enumerate
@item
For each library or program module not yet configured, run
@code{configure}, adding the configure option @code{--disable-build}
if the module need not be built, otherwise running @code{make all}.

@item
For each library or program module that must be built, run
@code{make} for the selected target(s): @code{default} or
@code{all} to (re-)build, @code{check} to run tests, @code{install},
etc.

@end enumerate

Running the top-level @code{make} a second time iterates again over
all the library and program modules, and finds (should find) nothing
to be done.

@node Build in parallel
@section Build in parallel

@cindex building in parallel
@cindex parallel build
@cindex cache for @code{configure}

@cindex dependencies, with several output files
@vindex -j make @r{option}
The TL build system carefully formulates dependencies as well as
@code{make} rules when a tool (such as @code{tangle}, @code{ctangle},
and @code{convert}) creates several output files.  This allows for
parallel builds (@code{make -j @var{n}} with @math{@var{n}>1} or even
@code{make -j}) that can considerably speed up the TL build.

@vindex TL_MAKE_FLAGS
If you're using TL's @code{Build} script, you can enable @code{-j}
with the environment variable @code{TL_MAKE_FLAGS}, as in:
@samp{env TL_MAKE_FLAGS=-j`nproc` ./Build}.

@cindex cache file, for @code{configure}
@vindex -C configure @r{option}
Independently, a noticeable speed-up can also be gained by using a
configure cache file, i.e., specifying the @code{configure} option
@code{-C} (recommended).

@node Build distribution
@section Build distribution

@cindex building a distribution
@cindex distribution tarball, making

@cindex @code{dist} and @code{distcheck} targets for @code{make}
Running @code{make dist} at the top level creates a tarball
@file{tex-live-@var{yyyy}-@var{mm}-@var{dd}.tar.xz} from the TL source
tree.  Running @code{make distcheck} also verifies that this tarball
suffices to build and install all of TL.

This is useful for checking consistency of the source tree and
Makefiles, but the result is not a complete or even usable @TeX{}
system, since all the support files are lacking; @pxref{Installing}.
We do not actually distribute any such tarball, and have no plans to
do so.

@node Build one package
@section Build one package

@cindex build one package
@cindex one package, building

@vindex --disable-all-packages
@cindex build on demand
To build one package, the basic idea is to use the @code{configure}
option @code{--disable-all-pkgs} (@pxref{@code{--disable-all-pkgs}}).
Then all program and library modules are configured but none are made.
However, the @file{Makefile}s still contain all build rules and
dependencies and can be invoked to build an individual program or
library, first building any required libraries.

Here is an example from start to finish for working on
@code{dvipdfm-x}.  Unfortunately, this does not suffice for building
the @TeX{} engines; see the next section.

@example
mkdir mydir && cd mydir  # new working directory

# Get sources (@url{https://tug.org/texlive/svn}), e.g.:
rsync -a --delete --exclude=.svn --exclude=Work \
      tug.org::tldevsrc/Build/source/ .

# Create build directory:
mkdir Work && cd Work

# Do the configure:
../configure --disable-all-pkgs --enable-dvipdfm-x \
  -C CFLAGS=-g CXXFLAGS=-g >&outc || echo fail

# Do the make:
make >&outm || echo fail

# Run the tests:
cd texk/dvipdfm-x
make check

# Run the new binary in the build tree, finding support files
# in a separate tree for a TeX Live release YYYY
# (Bourne shell syntax):
TEXMFROOT=/usr/local/texlive/YYYY \
TEXMFCNF=$TEXMFROOT/texmf-dist/web2c \
./xdvipdfmx ...
@end example

@vindex TEXMFROOT @r{for running standalone}
@vindex TEXMFCNF @r{for running standalone}

Then you can modify source files in @file{mydir/texk/dvipdfm-x} and
rerun @code{make} in @file{mydir/Work/texk/dvipdfm-x} to rebuild; that
build directory is where the binary ends up and where you can run a
debugger, etc.

The second line of the @code{configure} invocation shows examples of
extra things you likely want to specify if you intend to hack the
sources (and not just build binaries): the @code{-C} speeds
@code{configure} by enabling a cache file, and the @code{CFLAGS} and
@code{CXXFLAGS} settings eliminate compiler optimization for debugging
purposes.

Of course, you need to actually look at the output and check that
things are working.  There are many @code{configure} options you can
tweak as desired; check the output from @code{configure --help}.  It
is also a good idea to run @code{make check} after making any changes,
to ensure that whatever tests have been written still pass.

@subsubheading Reducing source download size

@cindex size of source tree
The above retrieves the entire TL source tree (several
hundred megabytes). It is natural to ask if this is really necessary.
Strictly speaking, the answer is no, but it is vastly more convenient
to do so. If you cut down the source tree, you must also give
additional @code{configure} flags to individually disable using system
versions of libraries, or the intricacies of the dependencies (such as
@code{teckit} requiring @code{zlib}) will have undesired side effects.
For an example of this approach, see the @code{build-pdftex.sh} script
in the @code{pdftex} development source (details at
@url{http://pdftex.org}), which is indeed such a cut-down TL source
tree.

@subsubheading GCC used by default

@vindex CC=@var{c-compiler}
@vindex CXX=@var{c++-compiler}
@vindex OBJCXX=@var{objc-compiler}
@pindex gcc@r{, default compilers}
By default, the @code{gcc} compilers will be used if present;
otherwise, individual packages may use something different.  You can
explicitly specify the compilers to be used with the environment
variables @code{CC}, @code{CXX}, and @code{OBJCXX}.

@subsubheading Removing C+11 dependency

@cindex C++11, removing dependent sources
Some libraries and programs require C++11; one such is XeTeX.  If you
want to build with an older compiler lacking such support, you need to
(re)move those source directories; unfortunately, specifying
@code{--disable} for them does not suffice.  It's also necessary to
specify @code{--disable-xetex} explicitly. Specifically, before
running @code{configure --disable-xetex ...}:

@example
rm -rf libs/icu libs/graphite2 texk/dvisvgm texk/web2c/xetexdir
@end example

@vindex --enable-missing @r{to ignore dependencies}
Also, even with @code{--disable-all-pkgs}, dependencies are (currently)
checked.  One notable case: if a (non-MacOS) system does not have
@code{fontconfig}, Xe@TeX{} cannot be built (@pxref{Prerequisites}),
and @code{configure} will terminate even with @code{--disable-xetex}.
To proceed without such dependencies, specify @code{--enable-missing}
also.

As of 2022, HarfBuzz also requires C++11.  Therefore even more would
have to be disabled and removed, notably including @code{luahbtex},
the standard engine used for Lua@LaTeX{}.  Removing that would not
be acceptable for builds intended for distribution; but perhaps for
testing the above information could still be useful.

@cindex removing build directories
@cindex @code{configure} problems, work around by removing
In general, the TL @code{configure} will run in all directories.
Therefore a general workaround for build problems is to remove failing
directories from the tree, and also specify the relevant
@code{--disable-...} option(s).

Patches to improve all this would be most welcome.

@node Build one engine
@section Build one engine

@cindex build one engine
@cindex one engine, building
@cindex engine, building one

Unfortunately, there is one common case where the steps in the
preceding section to build one package (@pxref{Build one package}) do
not suffice: wanting to build one, or a subset, of the @TeX{} engines
(or other Web2c programs).

The simplest way to do this is to disable everything and then
explicitly specify what to make. For example, to build only the
original @TeX{}:

@example
cd Work        # top build directory
../configure --without-x --disable-shared --disable-all-pkgs \
             --enable-tex --disable-synctex --disable-xetex \
             --enable-missing -C CFLAGS=-g CXXFLAGS=-g
make
cd texk/web2c  # cd engine build directory
make tex       # must specify target
@end example

The first @code{make} run will configure everything, and even build
the libraries, even though the packages are disabled.

The source tree can be cut down to just what is needed for the given
engine (the separate pdf@TeX{} and Lua@TeX{} source repositories do
this, for example), but see caveats in previous section.  When the
@code{--disable-xetex} and @code{--enable-missing} options are needed
is also explained in the previous section.

If you want to debug an X-related program or shared library setup, or
other variants, change the @code{configure} options
accordingly. Either @code{../Build} or @code{../configure} can be run.

Then it is necessary to again specify the target engine (@code{tex},
in the above) in the @code{make}.

All these complications are rather unfortunate.  Patches are welcome.

@subsubheading Testing one engine

To run only the tests for a given engine, say @code{hitex}:

@example
make -C $ww check SUBDIRS=. TESTS='$(hitex_tests)' 
@end example

@noindent where @code{$ww} is the web2c build directory, that is,
@file{ww=/wherever/Build/source/Work/texk/web2c}.

It's also possible to run individual tests the same way, using the test
name exactly as specified in the @file{.am} file:

@example
make -C $ww check SUBDIRS=. TESTS=hitexdir/tests/hello.test
@end example

Without the @code{SUBDIRS=.}, errors like this will show up, since
@code{make} will descend into every directory.

@example
fatal: making test-suite.log: failed to create hitexdir/tests/hello.test
@end example

@vindex --no-print-directory @r{GNU make option}
If you get tired of looking at the @samp{Entering}/@samp{Leaving
directory} lines, you can add the (GNU) make option
@code{--no-print-dir}.

You may find it useful to put lengthy incantations like this into a
trivial shell script with a short name (say, @code{hitst}).  Then you
just run @code{hitst} and edit the file when necessary to change
things around.

@node Cross compilation
@section Cross compilation

@cindex cross compilation
In a cross compilation a @dfn{build} system is used to create
binaries to be executed on a @dfn{host} system with different
hardware and/or operating system.

@cindex native cross compilation
In simple cases, the build system can execute binaries for the host
system.  This typically occurs for bi-arch systems where, e.g.,
@code{i386-linux} binaries can run on @code{x86_64-linux} systems and
@code{win32} binaries can run on @code{win64} systems.  Although
sometimes called ``native cross'', technically this is not cross
compilation at all.  In most such cases it suffices to specify
suitable compiler flags.  It might be useful to add the configure
option @code{--build=@var{host}} to get the correct canonical host
name, but note that this should @emph{not} be @code{--host=@var{host}}
(@pxref{Hosts and Cross-Compilation,,, autoconf, GNU Autoconf}).

In order to build, e.g., 32-bit binaries with @command{clang} on a 64-bit
MacOS system one could use:

@example
TL_BUILD_ENV="CC='clang -arch i386' \
  CXX='clang++ -arch i386' \
  OBJCXX='clang++ -arch i386'" \
  ./Build --build=i386-apple-darwin
@end example

@menu
* Cross configuring::           Configuring for cross compilation.
* Cross problems::              Cross compilation problems.
@end menu

@node Cross configuring
@subsection Cross configuring

@cindex cross compilation configuring
@cindex configuring, for cross compilation

@vindex --host=@var{host}
@vindex --build=@var{host}
In a standard cross compilation, binaries for the host system cannot
execute on the build system and it is necessary to specify the
configure options @code{--host=@var{host}} and
@code{--build=@var{build}} with two different values.

Building binaries requires suitable ``cross'' tools, e.g., compiler,
linker, and archiver, and perhaps a ``cross'' version of
@code{pkg-config} and similar to locate host system libraries.
Autoconf expects that these cross tools are given by their usual
variables or found under their usual name prefixed with
@code{@var{host}-}.  Here a list of such tools and corresponding
variables:

@example
@code{ar}                AR
@code{freetype-config}   FT2_CONFIG
@code{g++}               CXX
@code{gcc}               CC
@code{icu-config}        ICU_CONFIG
@code{objdump}           OBJDUMP
@code{pkg-config}        PKG_CONFIG
@code{ranlib}            RANLIB
@code{strip}             STRIP
@end example

@cindex @code{mingw32}
@noindent In order to, e.g., build @code{mingw32} binaries on
@code{x86_64-linux} with a cross compiler found as
@file{i386-pc-mingw32-gcc} one would specify

@example
--host=i386-pc-mingw32 --build=x86_64-linux-gnu
@end example

@noindent or perhaps

@example
--host=mingw32 --build=x86_64-linux CC=i386-pc-mingw32-gcc
@end example

@noindent but this latter, especially, might require adding @code{CXX} and others.

Configure arguments such as @code{CFLAGS=@dots{}} refer to the cross
compiler.  If necessary, you can specify compilers and flags for the
few auxiliary C and C++ programs required for the build process as
configure arguments

@vindex BUILDCC@r{,} BUILDCFLAGS@r{, @dots{}}
@example
BUILDCC=@dots{}
BUILDCPPFLAGS=@dots{}
BUILDCFLAGS=@dots{}
BUILDCXX=@dots{}
BUILDCXXFLAGS=@dots{}
BUILDLDFLAGS=@dots{}
@end example

@node Cross problems
@subsection Cross problems

@cindex cross compilation problems

The fact that binaries for the host system cannot be executed on the
build system causes some problems.

One problem is that configure tests using @code{AC_RUN_IFELSE} can
compile and link the test program but cannot execute it.  Such tests
should be avoided if possible and otherwise must supply a pessimistic
test result.

@pindex squeeze
@pindex web2c @r{program}
@cindex @code{freetype} cross compiling
@vindex CC_BUILD
Another problem arises if the build process must execute some
(auxiliary or installable) programs.  Auxiliary programs can be placed
into a subdirectory that is configured natively as is done for
@file{texk/web2c/web2c}, @file{texk/dvipsk/squeeze}, and
@file{texk/xdvik/squeeze}.  The module @file{libs/freetype2} uses the
value of @code{CC_BUILD}, @file{@var{build}-gcc}, @file{gcc}, or
@file{cc} as the compiler for the auxiliary program.

@cindex ICU cross compiling
The situation for installable programs needed by the build process is
somewhat different.  A rather expensive possibility, chosen for the ICU
libraries in module @file{libs/icu}, is to first compile natively for
the build system and in a second step to use these (uninstalled)
programs during the cross compilation.

@pindex tangle
@pindex ctangle
@pindex otangle
@pindex tie
This approach would also be possible for the tools such as
@file{tangle} used in the module @file{texk/web2c} to build the WEB
programs, but that would require first building a native
@code{kpathsea} library.  To avoid this complication, cross
compilation of programs written in (C)WEB requires sufficiently recent
installed versions of @file{tangle}, @file{ctangle}, @file{otangle},
and @file{tie}.

@cindex @code{xindy} cross compiling requires @code{clisp}
Building @code{xindy} requires running the host system @code{clisp}
binary, thus cross compilation is painful, but possible.

@node Installing
@chapter Installing

@cindex installing
This section discusses the results of @code{make install} in the
source tree.

@cindex support files, separate from build
@pindex texlive.tlpdb@r{, @TL{} database}
@pindex install-tl@r{, @TL{} installer}
@pindex plain.tex@r{, not in source tree}
The main consideration is that @code{make install} is not enough to
make a usable @TeX{} installation.  Beyond the compiled binaries,
(thousands of) support files are needed; just as a first example,
@file{plain.tex} is not in the source tree.

These support files are maintained completely independently and are
not present in the TL source tree.  The best basis for dealing with them
is the @TL{} (plain text) database in
@file{Master/tlpkg/texlive.tlpdb}, and/or the @TL{} installer,
@code{install-tl}.  More information is under @file{Master/tlpkg} and
at @url{https://tug.org/texlive/distro.html}.

@menu
* Installation directories::    The prefix, @code{bindir}, etc., directories.
* Linked scripts::              Scripts not maintained in the sources.
* Distro builds::               Configuring and building for OS distributions.
@end menu

@node Installation directories
@section Installation directories

@cindex installation directories
@cindex directories, for installation
@cindex paths, for installation

Running @code{make install} (or @code{make install-strip}) installs
executables in @code{@var{bindir}}, libraries in @code{@var{libdir}},
headers in @code{@var{includedir}}, general data (including ``linked
scripts'', @pxref{Linked scripts}) in
@code{@var{datarootdir}/texmf-dist}, man pages in @code{@var{mandir}},
and Info files in @code{@var{infodir}}.

The values of these directories are determined by @code{configure}
and can be specified explicitly as options such as
@code{--prefix=@var{prefix}} or @code{--bindir=@var{bindir}};
otherwise, they are given by their usual Autoconf defaults:

@example
@var{prefix}                  /usr/local
@var{exec_prefix}             @var{prefix}
@var{bindir}                  @var{exec_prefix}/bin
@var{libdir}                  @var{exec_prefix}/lib
@var{includedir}              @var{prefix}/include
@var{datarootdir}             @var{prefix}/share    
@var{mandir}                  @var{datarootdir}/man
@var{infodir}                 @var{datarootdir}/info
@end example

@noindent except possibly modified as follows:

@itemize @bullet
@item
If the option @code{--enable-multiplatform} is given,
@code{/@var{platform}} (i.e., the canonical platform name) is appended
to @code{@var{bindir}} and @code{@var{libdir}}.  This is implied for a
native TL build.

@item
@raggedright
In a native TL build, @code{@var{datarootdir}} is set to
@code{@var{prefix}}, @code{@var{infodir}} is set to
@code{@var{prefix}/texmf-dist/doc/info}, and @code{@var{mandir}} to
@code{@var{prefix}/texmf-dist/doc/man}, corresponding to the
directories used in the TL distribution.
@end raggedright

@end itemize

@noindent The top-level @file{configure} script displays all these
installation paths.

For the native TL build, the @code{Build} script leaves the binaries
in @file{./inst/bin/@var{std-system-triplet}}.  The new binaries are
not directly usable from that location; they need to be copied to
@file{Master/bin/@var{tl-platform}}.  The other files and directories
that end up in @file{./inst/} are ignored.

@node Linked scripts
@section Linked scripts

@cindex linked scripts
@cindex scripts, linked and not maintained

@cindex symlinks, used for scripts
@cindex wrapper binary for scripts on Windows
@cindex Windows, invoking scripts on
Quite a few executables are architecture-independent shell, Perl, or
other interpreted scripts, rather than compiled binaries.  A few are
maintained as part of the TL source tree, but most are maintained
elsewhere with copies under @file{texk/texlive/linked_scripts}.

These so-called @dfn{linked scripts} are installed under
@code{@var{datarootdir}/texmf-dist/scripts}; for Unix-like systems a
symbolic link is made in @code{@var{bindir}}.  For example, a symlink
points from @code{@var{bindir}/ps2eps} to
@code{@var{datarootdir}/texmf-dist/scripts/ps2eps/ps2eps.pl}.  For
Windows, a standard wrapper binary (copied to, e.g.,
@code{@var{bindir}/ps2eps.exe}) serves the same purpose.  The source
for the wrapper is in @file{texk/texlive/windows_wrapper}.

One reason for this is to avoid having many copies of the same
script; a more important reason is that it guarantees the scripts will
stay in sync across the different supported operating systems.

@pindex asymptote
@pindex biber
@pindex xindy
@pindex xz
@pindex wget
Most important of all, we want the @code{@var{bindir}} resulting from
the build to be as close as possible to what is in the TL
distribution.  At present, there are a few exceptions---Asymptote,
Biber, Xindy---and each one creates considerable extra work.  We don't
want to add more.  (See @url{https://tug.org/texlive/build.html} for
information about building those exceptions, as well as the @code{xz}
and @code{wget} programs that are used in the TL infrastructure.)

@node Distro builds
@section Distro builds

@cindex distro, building for
@cindex operating system distribution, building for
@cindex system distribution, building for

@cindex GNU/Linux distro
@cindex BSD distro
Although they use the same code base, building for the native TL
distribution as shipped by the @TeX{} user groups is typically quite
different from a ``distro'' build needed by, e.g., a full GNU/Linux or
BSD operating system distribution.

@cindex shared libraries, using vs.@: avoiding
The native TL distribution uses shared libraries only when absolutely
necessary (@file{libc}, @file{libm}, X11 libraries, and
@file{libfontconfig}).  In contrast, a distro typically wants to use
as many shared libraries as possible from elsewhere on the system,
including @TeX{}-specific libraries such as @file{libkpathsea} (even
though Kpathsea has never officially been released as a shared
library).  In addition, the installation paths will, in general, be
completely different.

Here are the @code{configure} options that distro builds are likely to
find most relevant:

@table @code
@item --disable-native-texlive-build
This must be specified to avoid interference from the many tweaks we
do for the native TL build.

@item --with-banner-add=/@var{SomeDistro}
This isn't technically required, but is strongly recommended, so your
build and your distro can be distinguished from others.

@item --enable-shared
Build shared versions of the @TeX{}-specific libraries (uses
@code{libtool}).

@item --disable-static
Do not build the static versions of the @TeX{}-specific libraries.

@item --with-system-@var{lib}
Look for and use a system version of the library @var{lib}.
@code{configure --help} will give you the list of possibilities.

@item --with-@var{lib}-includes=@var{dir}
@itemx --with-@var{lib}-libdir=@var{dir}
If needed, allows you to specify where the headers/code are for the
given library @var{lib}.

@item --prefix=/usr
@itemx --prefix=/opt/TeXLive
Or whatever your convention is.  The default is @file{/usr/local} and
you shouldn't install there for a distro.

@item --libdir=\$@{exec_prefix@}/lib64
May be needed for 64-bit bi-architecture (GNU/Linux) systems.

@end table

@cindex Preining, Norbert
@cindex adapting @TL{} for distros
You will need to take care of the support files mentioned above
(@pxref{Installing}), and many other issues, such as font maps,
languages, and formats, independently of the build.  Norbert Preining
has written a detailed article on adapting TL for distros:
@url{https://tug.org/TUGboat/tb34-3/tb108preining-distro.pdf}.  (If the
article needs updating in the future, perhaps we will merge it into
this document.)

@node Layout and infrastructure
@chapter Layout and infrastructure

@cindex layout of sources
@cindex source tree

The @TL{} source tree is the subtree rooted at @file{Build/source} of
the complete TL distribution and contains the sources for all executables
distributed by TL, as well as @code{configure} scripts and @code{make}
rules to build and install them together with some of their support
files.

@menu
* Build system tools::      Modifying infrastructure files.
* Top-level directories::   libs texk utils; am auxdir build-aux m4; doc extra.
* Autoconf macros::         TL-specific Autoconf macros.
* Library modules::         Handling libraries, with examples.
* Program modules::         Handling programs, with examples.
* Extending @TL{}::         Adding a new module.
@end menu

@node Build system tools
@section Build system tools

@cindex tools, for building
@cindex GNU tools, needed for building
@cindex infrastructure, tools needed for

As mentioned above (@pxref{Prerequisites}), a normal build has few
requirements.  On the other hand, if you want to modify the @TL{}
infrastructure sources, such as @file{configure.ac} or
@file{Makefile.am} files, you will need to have several additional
tools installed.

In general, the TL build system uses the latest released versions of
the GNU build tools, installed directly from the original GNU releases
(e.g., by building them with @code{configure --prefix=/usr/local/gnu}
and having @env{PATH} start with @file{/usr/local/gnu/bin}).  We have
found that trying to use the versions of these tools packaged for
distros causes many extra hassles, so don't do that, tempting as it
may be.

Currently the versions we use are:

@display
@include build-tools.txt
@end display

@pindex reautoconf
@vindex --enable-maintainer-mode
These versions should be used to update the generated files (e.g.,
@file{configure} or @file{Makefile.in}) in all or parts of the TL tree
after their dependencies have been changed.  This can be done
explicitly with the top-level @code{reautoconf} script or implicitly
by using the configure option @code{--enable-maintainer-mode}.

It has often turned out that the bison and flex versions are not
critical; however, the autotools versions are.  If you don't have the
given versions, get them before modifying the build infrastructure.

@cindex Subversion repository
@cindex timestamps, in repository
@vindex use-commit-times@r{, Subversion}
The files in the Subversion repository (see
@url{https://tug.org/texlive/svn}) are all up to date (barring
bugs). For this to be reflected by their timestamps in your checkout,
be sure to set @file{use-commit-times=yes} in
@file{~/.subversion/config} or the equivalent.

@cindex touching files to avoid rerunning
@pindex make -t
If timestamps are wrong, you may also be able to avoid unnecessary
runs of @code{bison}, @code{flex}, or @code{makeinfo} with
@code{touch} of the generated (@file{.c}, @file{.h}, or @file{.info})
files.  With @code{--enable-maintainer-mode} it may also be necessary
to @code{touch} first @file{aclocal.m4}, then @file{configure} and
@file{config.h.in} (or @file{c-auto.in}), and finally all
@file{Makefile.in} files.

@node Top-level directories
@section Top-level directories

@cindex directories, top-level
@cindex top-level directories

Here is a brief description of the top-level directories in the @TL{}
source tree.

As mentioned at the beginning of @pxref{Overview of build
system}, the main source directories are @file{texk/}
(@TeX{}-specific programs and libraries), @file{utils/} (additional
programs), and @file{libs/} (generic libraries).

@cindex @file{am/} top-level directory
@cindex @file{m4/} top-level directory
In addition, the top-level directories @file{am/} and @file{m4/}
contain @file{Makefile.am} fragments and Autoconf macros,
respectively, used in many places.  Specifically, the file
@file{m4/kpse-pkgs.m4} contains lists of all program and library
modules; missing modules are silently ignored.  (This helps in
creating cut-down source trees.)

Each module contributes fragments (in separate files) defining its
capabilities and requirements to the @file{configure.ac} scripts at
the top-level and in the subdirectories @file{libs}, @file{utils}, and
@file{texk}.  The fragments from program modules supply
@code{configure} options to disable or enable building them; those
from library modules specify if an installed (system) version of that
library can be used.  This ultimately determines which modules need to
be built---although all modules must be configured for the benefit of
@file{make} targets such as @code{dist} or @code{distcheck}.

@cindex @file{build-aux/} top-level directory
@pindex config.guess@r{,} config.sub, @dots{}
@cindex Gnulib, used for common files
The top-level @file{build-aux/} directory contains the common files
@file{compile}, @file{config.guess}, @file{config.sub},
@file{depcomp}, etc.@ used by most packages.  These are taken from the
GNU Gnulib sources (@url{https://www.gnu.org/software/gnulib}), which
in turn synchronizes with any ultimate upstream repository.  There are
independent copies of some of these in a few other places, e.g.,
@file{libs/freetype2/freetype-*/builds/unix/}.  The @code{reautoconf}
script does not touch those, but a TL cron job keeps them in sync
(nightly).

@cindex @file{Work/} top-level directory
@cindex @file{inst/} top-level directory
When the top-level @file{./Build} script is used to build TL, two more
two more top-level directories appear: @file{Work/} for the build tree,
and @file{inst/} for the install tree (from @code{make install}).
These names (and everything else about @file{Build}'s operation) can
be changed by setting environment variables before running it; see the
script source.

@node Autoconf macros
@section Autoconf macros

@cindex autoconf macros

@c Texinfo macro: @ovar(ARG)
@c ARG is the name of an optional argument; this is used for
@c documentation of macro arguments (@defmac lines).  Plain
@c brackets are treated specially and appear more distinct.
@macro ovar{varname}
[@var{\varname\}]
@end macro

@c @dvar(ARG, DEFAULT)
@c -------------------
@c The ARG is an optional argument, defaulting to DEFAULT.  To be used
@c for macro arguments in their documentation (@defmac).
@c @macro xxdvar{varname, default}
@c @r{[}@var{\varname\} = @samp{\default\}@r{]}
@c @end macro

Here we describe a few of the Autoconf macros used in several
modules---many more are defined in the sources; see the top-level
@code{m4/} directory.  These general macros are supplemented by
module-specific macros in directories such as @file{texk/dvipng/m4/};
some of those are described in following sections (@pxref{Library
modules} and @ref{Program modules}).

@menu
* Setup:     General setup macros.
* Programs:  Macros for programs.
* Compilers: Macros for compilers.
* Libraries: Macros for libraries.
* Flags:     Macros for library and header flags.
* Windows:   Macros for Windows.
@end menu

@node General setup macros
@subsection General setup macros

@cindex general setup macros
@cindex setup macros, general
@cindex macros, general setup
The TL sources use two general setup macros:

@defmac KPSE_BASIC (@var{name}, @ovar{more-options})
Initialize the basic TL infrastructure for module @var{name}:@*@ @ @
@code{AM_INIT_AUTOMAKE([foreign @var{more-options}])}@*@ @ @
@code{AM_MAINTAINER_MODE}@*@ @ @ @code{KPSE_COMPILER_WARNINGS}@*
and make sure the C compiler understands function prototypes.  This is
used for all generic library and program modules.
@end defmac

@defmac KPSE_COMMON (@var{name}, @ovar{more-options})
Like @code{KPSE_BASIC} but add:@*@ @ @ @code{LT_PREREQ([2.2.6])}@*@ @
@ @code{LT_INIT([win32-dll])}@*@ @ @ @code{AC_SYS_LARGEFILE}@*@ @ @
@code{AC_FUNC_FSEEKO}@*along with checks for frequently used functions,
headers, types, and structures.  This is used for @TeX{}-specific
modules.
@end defmac

@node Macros for programs
@subsection Macros for programs

@cindex macros, for programs
Macros for program checks:

@defmac KPSE_CHECK_LATEX
Set @code{LATEX} to the first of @code{latex}, @code{elatex}, or
@code{lambda} which exists in @code{PATH}, or to @code{no} if none of
them exists.  Call @code{AC_SUBST} for @code{LATEX}.  The result of
this test can be overridden by setting the @code{LATEX} environment
variable or the cache variable @code{ac_cv_prog_LATEX}.
@end defmac

@defmac KPSE_CHECK_PDFLATEX
Check for @code{pdflatex} in @code{PATH} and set @code{PDFLATEX}.
@end defmac

@defmac KPSE_CHECK_PERL
Check for @code{perl} or @code{perl5} in @code{PATH} and set
@code{PERL}.
@end defmac

@defmac KPSE_PROG_LEX
Call @code{AC_PROG_LEX} and add the flag @code{-l} for @code{flex}.
@end defmac

@node Macros for compilers
@subsection Macros for compilers

@cindex macros, for compilers

Macros for compiler-related checks:

@defmac KPSE_COMPILER_WARNINGS
@vindex WARNING_C[XX]FLAGS
When using the (Objective) C/C++ compiler, set
@code{WARNING_[OBJ]C[XX]FLAGS} to suitable warning flags (depending on
the value given to or implied for @code{--enable-compiler-warnings}).
Call @code{AC_SUBST} for them.  At present this assumes GNU compiler
warning options, but could be extended to others if necessary.

@vindex kpse_cv_warning_cflags
This macro caches its results in the @code{kpse_cv_warning_cflags},
@dots{} variables.
@end defmac

@defmac KPSE_COMPILER_VISIBILITY
When using the C or C++ compiler, try to set
@code{VISIBILITY_C[XX]FLAGS} to flags to hide external symbols.  Call
@code{AC_SUBST} for this variable.  At present this only tests for
the compiler option @code{-fvisibility=hidden}, but could be
extended if necessary.

@vindex kpse_cv_visibility_c[xx]flags
This macro caches its results in the @code{kpse_cv_visibility_cflags}
or @code{kpse_cv_visibility_cxxflags} variable.
@end defmac

@defmac KPSE_CXX_HACK
@cindex static linking for C++
@cindex linking C++ libraries statically
@vindex --enable-cxx-runtime-hack
@pindex libstc++@r{, statically linking}
Provide the configure option @code{--enable-cxx-runtime-hack}.  If
enabled and when using @code{g++}, try to statically link with
@file{libstdc++}, notably improving portability of the resulting
binary.

@vindex kpse_cv_cxx_hack
This macro caches its result in the @code{kpse_cv_cxx_hack} variable.
@end defmac

@node Macros for libraries
@subsection Macros for libraries

@cindex macros, for libraries
One macro for a library check:

@defmac KPSE_LARGEFILE (@var{variable}, @ovar{extra-define})
Call @code{AC_SYS_LARGEFILE} and @code{AC_FUNC_FSEEKO} and append
suitable @code{-D} flags (optionally including
@code{-D@var{extra-define}}) to @var{variable}.
@end defmac

@node Macros for library and header flags
@subsection Macros for library and header flags

@cindex macros, for library and header flags
@cindex flags, macros for library and header
@vindex KPSE_@var{LIB}_FLAGS
Each library module @file{libs/@var{lib}} or @file{texk/@var{lib}} is
supplemented by a macro @code{KPSE_@var{LIB}_FLAGS} (all uppercase)
that provides make variables for that library.  E.g., for
@file{libs/libpng}:

@defmac KPSE_LIBPNG_FLAGS
Provide the configure option @code{--with-system-libpng}.  Set and
@code{AC_SUBST} @code{make} variables for modules using this library (either
an installed version or from the @TL{} tree):

@multitable {@code{LIBPNG_INCLUDES}} {for the @code{make} rules to rebuild the library.}
@item @code{LIBPNG_INCLUDES}
@tab for use in @code{CPPFLAGS},
@item @code{LIBPNG_LIBS}
@tab for use in @code{LDADD},
@item @code{LIBPNG_DEPEND}
@tab for use as a Makefile dependency,
@item @code{LIBPNG_RULE}
@tab for the @code{make} rules to rebuild the library.
@end multitable
@end defmac

@defmac KPSE_ADD_FLAGS (@var{name})
Temporarily extend @code{CPPFLAGS} and @code{LIBS} with the values required
for the library module @code{@var{name}}.
@end defmac

@defmac KPSE_RESTORE_FLAGS
Restore @code{CPPFLAGS} and @code{LIBS} to their original values.
@end defmac

As an example, the @file{configure.ac} file for a hypothetical program
@file{utils/foo} using @file{libpng}, and hence @file{zlib}, would
contain
@example
KPSE_ZLIB_FLAGS
KPSE_LIBPNG_FLAGS
@end example

@noindent and its @file{Makefile.am} would be along these lines:
@example
bin_PROGRAMS = foo
AM_CPPFLAGS = $@{LIBPNG_INCLUDES@} $@{ZLIB_INCLUDES@}
foo_LDADD = $@{LIBPNG_LIBS@} $@{ZLIB_LIBS@}
foo_DEPENDENCIES = $@{ZLIB_DEPEND@} $@{LIBPNG_DEPEND@}
## Rebuild libz
@@ZLIB_RULE@@
## Rebuild libpng
@@LIBPNG_RULE@@
@end example

If it were necessary to examine whether certain @file{zlib} or
@file{libpng} features were available, @file{configure.ac} should be
continued this way:
@example
KPSE_ADD_FLAGS([zlib])
@dots{} # @r{tests for @file{zlib} features, if any}
KPSE_ADD_FLAGS([libpng])
@dots{} # @r{tests for @file{libpng} features}
KPSE_RESTORE_FLAGS # @r{restore @code{CPPFLAGS} and @code{LIBS}}
@end example

@node Macros for Windows
@subsection Macros for Windows

@cindex macros, for Windows
@cindex Windows, macros for
Windows differs in several aspects from Unix-like systems, many of
them due to the lack of symbolic links.

@defmac KPSE_CHECK_WIN32
@vindex kpse_cv_have_win32
Check if compiling for a Windows system.  The result is either
@code{no} for Unix-like systems (including Cygwin), @code{mingw32} for
Windows with GCC, or @code{native} for Windows with MSVC.  The result
is cached in the @code{kpse_cv_have_win32} variable.
@end defmac

@defmac KPSE_COND_WIN32
@vindex WIN32@r{, Automake conditional}
Call @code{KPSE_CHECK_WIN32} and define the Automake conditional
@code{WIN32} (@code{true} if the value of @code{kpse_cv_have_win32} is
not @code{no}).
@end defmac

@defmac KPSE_COND_MINGW32
@vindex MINGW32@r{, Automake conditional}
Call @code{KPSE_COND_WIN32} and define the Automake conditional
@code{MINGW32} (@code{true} if the value of @code{kpse_cv_have_win32} is
@code{mingw32}).
@end defmac

@defmac KPSE_COND_WIN32_WRAP
@vindex WIN32_WRAP@r{, Automake conditional}
@pindex runscript.exe
Call @code{KPSE_COND_WIN32} and define the Automake conditional
@code{WIN32_WRAP} (@code{true} if the standard Windows wrapper
(@file{texk/texlive/windows_wrapper/runscript.exe}) exists.  This wrapper
is used on Windows instead of symlinks for the ``linked scripts''
(@pxref{Linked scripts}).
@end defmac

@defmac KPSE_WIN32_CALL
@pindex callexe.c
Call @code{KPSE_COND_WIN32} and check if the file
@file{texk/texlive/windows_wrapper/callexe.c} exists; if it does, create a
symlink in the build tree.  Compiling @file{callexe.c} with
@code{-DEXEPROG='"@var{foo}.exe"'} and installing @file{callexe.exe}
as @code{@var{bar}.exe} is used on Windows instead of a symlink
@code{@var{bar}->@var{foo}} for Unix-like systems.
@end defmac

@node Library modules
@section Library modules

@cindex library modules
@cindex modules, for libraries
Here we discuss some specifics for a few of the libraries in TL, both
for the details themselves, and as a way of illuminating the general
structure and variation.

@menu
* @code{png} library::       @file{libs/libpng}
* @code{zlib} library::      @file{libs/zlib}
* @code{freetype} library::  @file{libs/freetype2}
* @code{kpathsea} library::  @file{texk/kpathsea}
@end menu

@node @code{png} library
@subsection The @code{png} library in @file{libs/libpng}

@pindex png @r{library}
@pindex libpng @r{library}
The ``generic'' @code{png} library uses the source tree in the
subdirectory @file{libpng-src/}, with all modifications for TL
recorded in @file{TLpatches/*}.  The @file{configure.ac} fragment
@file{ac/withenable.ac} contains

@example
KPSE_WITH_LIB([libpng], [zlib])
@end example

@noindent to specify the module name and indicate the dependency on
@code{zlib}.  A third literal argument `@code{tree}' would specify that
the library from the @TL{} tree cannot be replaced by a system
version.  That not being the case here, a second fragment
@file{ac/libpng.ac} contains

@findex KPSE_TRY_LIB
@example
KPSE_TRY_LIB([libpng],
             [#include <png.h>],
             [png_structp png; png_voidp io; png_rw_ptr fn;
png_set_read_fn(png, io, fn);])
@end example

@noindent thus providing the simple C code

@example
#include <png.h>
int main ()
@{ png_structp png; png_voidp io; png_rw_ptr fn;
  png_set_read_fn(png, io, fn);
  return 0; @}
@end example

@findex KPSE_TRY_LIBXX
@noindent which Autoconf uses to verify the usability of a system
version with C code.  The analogous macro @code{KPSE_TRY_LIBXX} would
check using C++.  These fragments are included by the
@file{configure.ac} at the top level of TL
(@code{Build/source/configure.ac}).

@cindex proxy build system
For this library, like many other modules, a proxy build system for TL
is used, consisting of our own @file{configure.ac},
@file{Makefile.am}, @file{include/Makefile.am}; the distributed build
system is not used.  (Consequently, a few generated files and
auxiliary scripts are removed from the distributed source tree.)

The public headers @file{png.h}, @file{pngconf.h}, and
@file{pnglibconf.h} are ``installed'' (as symlinks) under
@file{include/} in the build tree exactly as they are for a system
version under, e.g., @file{/usr/include/}.

@pindex kpse-libpng-flags.m4
@vindex KPSE_LIBPNG_FLAGS
The module is supplemented by the file @file{m4/kpse-libpng-flags.m4}
that defines the M4 macro @code{KPSE_LIBPNG_FLAGS} used by all modules
depending on this library in their @file{configure.ac} to generate the
@code{make} variables @code{LIBPNG_INCLUDES} for use in
@code{CPPFLAGS}, @code{LIBPNG_LIBS} for use in @code{LDADD},
@code{LIBPNG_DEPEND} for use as dependencies, and @code{LIBPNG_RULE}
for the @code{make} rules to rebuild the library.

@file{m4/kpse-libpng-flags.m4} also supplies the configure option
@code{--with-system-libpng}, which then uses @code{pkg-config} to
determine the flags required for the system library.

@node @code{zlib} library
@subsection The @code{zlib} library in @file{libs/zlib}

@pindex zlib @r{library}

@pindex kpse-zlib-flags.m4
This generic library is very much analogous to @code{libpng}, but
without the dependency on any other library.  The file
@file{m4/kpse-zlib-flags.m4} supplies the configure option
@code{--with-system-zlib}, as well as @code{--with-zlib-includes} and
@code{--with-zlib-libdir} to specify non-standard locations of the
@code{zlib} headers and/or library.

@node @code{freetype} library
@subsection The @code{freetype} library in @file{libs/freetype2}

@pindex freetype @r{library}
@cindex wrapper build system

This module uses a wrapper build system.  In contrast to the proxy
build described earlier, the wrapper build has an almost trivial
@file{configure.ac} and a @file{Makefile.am} which invokes the
@code{configure} and @code{make} in the distributed source, followed
by @code{make install} with the TL build tree as destination.  In
other words, this actually uses the build system provided by upstream
(possibly patched).

@pindex freetype-config
The flags required for the system library are obtained through
@code{freetype-config}.

@node @code{kpathsea} library
@subsection The @code{kpathsea} library in @file{texk/kpathsea}

@pindex kpathsea @r{library}

This is one of the @TeX{}-specific libraries that are maintained as
part of @TL{} (@pxref{,,, kpathsea, Kpathsea
@r{(@url{tug.org/kpathsea})}}); the other is @code{ptexenc}.  These
@TeX{} libraries are Libtool libraries (static and/or shared) and are
installed by @code{make install} together with the programs.  They
are, however, not part of the TL DVD as distributed by @TeX{} user
groups, and have never been officially released for standalone use.

@pindex --with-system-kpathsea
It is possible, and probably useful for distro builds (@pxref{Distro
builds}), to specify the configure option
@code{--with-system-kpathsea} in order to use a system version of the
library.  Programs outside the TL tree should use @code{pkg-config}
for the required flags.

@pindex kpathsea.ac
@pindex mktex.ac
@vindex --enable-mktextfm-default
@pindex mktextfm
In addition to @file{kpathsea/ac/withenable.ac} and
@file{kpathsea/ac/kpathsea.ac} here there is a third fragment
@file{kpathsea.ac/mktex.ac}, included by both @file{withenable.ac} and
@file{configure.ac}, which supplies configure options such as
@code{--enable-mktextfm-default}. These determine the compile time
default of whether or not to run @code{mktextfm} (and similar) to
generate a missing @file{.tfm} (or whatever) file.  In any case,
however, the command line options @code{-mktex=tfm} or
@code{-no-mktex=tfm} for the @TeX{}-like engines override this
default.

@node Program modules
@section Program modules

@cindex program modules
@cindex modules, for programs
As with libraries (@pxref{Library modules}), here we discuss the
details for a few of the programs in TL.

@menu
* @code{t1utils} package:: @file{utils/t1utils}
* @code{xindy} package::   @file{utils/xindy}
* @code{xdvik} package::   @file{texk/xdvik}
* @code{asymptote}::       @file{utils/asymptote}
@end menu

@node @code{t1utils} package
@subsection The @code{t1utils} package in @file{utils/t1utils}

@pindex t1utils @r{package}

Here we use the distributed source tree @file{t1utils-src} with
modifications documented in @file{TLpatches/*} and a proxy build
system consisting of @file{configure.ac} and @file{Makefile.am}.  The
fragment @file{ac/withenable.ac} contains

@example
KPSE_ENABLE_PROG([t1utils])
@end example

@noindent specifying the module name without any dependencies, and
supplies the configure option @code{--disable-t1utils}.

@node @code{xindy} package
@subsection The @code{xindy} package in @file{utils/xindy}

@pindex xindy

This module uses the distributed source tree @file{xindy-src/} with
modifications documented in @file{TLpatches/*}, and a wrapper
@file{configure.ac} and @file{Makefile.am} that descends into
@file{xindy-src}.

The @code{xindy} build requires a @file{make} that supports a
@code{VPATH} build, can handle all targets, and does not refer to
@code{$@{top_srcdir@}} or @code{$@{top_builddir@}}.  The fragment
@code{xindy/ac/withenable.ac} contains

@example
KPSE_ENABLE_PROG([xindy], , [disable])
m4_include(kpse_TL[utils/xindy/ac/xindy.ac])
m4_include(kpse_TL[utils/xindy/ac/clisp.ac])
@end example

@noindent where @code{disable} in the third argument indicates that
@code{xindy} is only built if explicitly enabled by the user with
@code{configure --enable-xindy} (the need for @code{clisp} makes it
too painful to enable by default).

The additional fragments @file{ac/xindy.ac} and @file{ac/clisp.ac}
specify more @code{configure} options to be seen at the top level,
with @file{ac/xindy.ac} also included by @file{configure.ac}.

@node @code{xdvik} package
@subsection The @code{xdvik} package in @file{texk/xdvik}

@pindex xdvik

This package is maintained as part of the @TL{} tree with sources in
its own directory (@file{texk/xdvik/}).  The fragment
@code{xdvik/ac/withenable.ac} contains

@example
dnl extra_dirs = texk/xdvik/squeeze
KPSE_ENABLE_PROG([xdvik], [kpathsea freetype2], [x])
m4_include(kpse_TL[texk/xdvik/ac/xdvik.ac])
@end example

@pindex squeeze/configure.ac
@cindex cross compilation, with host binary
@noindent thus specifying dependencies on the @code{kpathsea},
@code{freetype}, and X11 libraries.  The M4 comment (following
@code{dnl}) signals the subsidiary @file{squeeze/configure.ac}.  This
is needed because the main executable @file{xdvi-bin} (to be installed
as, e.g., @file{xdvi-xaw}) is for the @code{host} system whereas the
auxiliary program @file{squeeze/squeeze} has to run on the
@code{build} system; in a cross compilation, these differ.

@vindex --with-xdvi-x-toolkit
The additional fragment @code{ac/xdvik.ac} is also included by
@file{configure.ac} and supplies the configure option
@code{--with-xdvi-x-toolkit} also seen at the top level.

@node @code{asymptote}
@subsection The subdirectory @file{utils/asymptote}

@pindex asymptote
@pindex xasy

@cindex OpenGL, required for Asymptote
This subdirectory contains the sources for @file{asy} and @file{xasy}
but due to its complexity and prerequisites (e.g., OpenGL) it is
not part of the TL build system.  These programs must be built and
installed independently, but are included on the TL DVD together with
their support files.  See @url{https://tug.org/texlive/build.html#asymptote}.

@node Extending @TL{}
@section Extending @TL{}

@cindex extending @TL{}
@cindex adding to @TL{}

This section outlines the basic process for adding new packages to the
TL build system.

In any case, a new package directory @file{foo} should contain the
original sources, modified only with changes necessary for TL, in
@file{foo/foo-src}. The changes should be documented in
@file{foo/TLpatches/*}, and also be submitted upstream whenever
reasonable.  In addition, @file{foo/} will need the usual Automake
build-related files (@file{configure.ac}, @file{Makefile.am}, etc.
Please maintain @file{foo/ChangeLog} for all TL changes.

@menu
* Adding a new program module::
* Adding a new engine::
* Adding a new generic library module::
* Adding a new @TeX{}-specific library module::
@end menu

@node Adding a new program module
@subsection Adding a new program module

@cindex adding a new program
@cindex program module, adding

@vindex kpse_texk_pkgs
A @TeX{}-specific program module in a subdirectory
@file{texk/@var{prog}} may use the @TeX{}-specific libraries and is
included by adding its name @file{@var{prog}} to the M4 list
@code{kpse_texk_pkgs} defined in @file{m4/kpse-pkgs.m4}.

@vindex kpse_utils_pkgs
A generic program module in a subdirectory @file{utils/@var{prog}}
must not use the @TeX{}-specific libraries and is included by adding
its name @file{@var{prog}} to the M4 list @code{kpse_utils_pkgs} in
@file{m4/kpse-pkgs.m4}.

@pindex withenable.ac@r{, for new modules}
@findex KPSE_ENABLE_PROG
In either case, the subdirectory @file{texk/@var{prog}} or
@file{utils/@var{prog}} must provide a fragment
@file{ac/withenable.ac} that contains the M4 macro
@code{KPSE_ENABLE_PROG} defined in @file{m4/kpse-setup.m4} with
@code{@var{prog}} as the mandatory first argument and three optional
arguments:

@enumerate
@item a list of required libraries from the TL tree;

@item a list of options: @code{disable} if this module is not to be
built without the configure option @code{--enable-@var{prog}},
@code{native} if cross compilation is not possible, @code{x} if the
program requires X11 libraries;

@item a comment added to the help text for the @code{configure}
option @code{--enable-@var{prog}} or @code{--disable-@var{prog}}.
@end enumerate

If the module requires specific @code{configure} options to be seen at
the top level, they should be defined in an additional fragment
@file{ac/@var{prog}.ac} included from @file{ac/withenable.ac} and
@file{configure.ac}.

@cindex @var{newprog-src}, original source subdirectory
Usually, the new program is maintained somewhere outside of @TL{}.  In
that case, as above, we put the upstream sources into a subdirectory
@file{@var{prog}-src} (e.g., @file{utils/newprog/newprog-src}).  We do
not typically run @code{configure} in this original @code{...-src}
directory, but only in our own directory; but we do compile using the
source files in @code{...-src}.

So, to summarize the files that must (usually) be created inside a new
TL source directory (@file{texk/newprog} or @file{utils/newprog}):

@ftable @file
@item ac/withenable.ac
The @code{KPSE_ENABLE_PROG} call just explained.

@item configure.ac
@itemx Makefile.am
By merging the contents of the original @file{configure.ac} (if
provided) and a comparable program already in TL.  In the above
example, one line that will be needed in @file{configure.ac} (can be
added before the @code{AC_CONFIG_FILES} at the end) is:

@example
AC_SUBST([NEWPROG_TREE], [newprog-src])
@end example

@noindent and then use @code{@@NEWPROG_TREE@@} in 
@code{Makefile.am} where needed.

In general, there is no magic recipe for this part of the job. It's
necessary to think about what needs to be done in the original vs.@:
in @TL{}. It's useful to look at the setup for the most comparable
programs already in TL that you can find. It's also useful to grep the
entire @file{Build/source} tree for whatever you can think of to
investigate how something is done. Most of the TL-specific macros are
defined in @file{Build/source/m4/*}.

@item TLpatches/TL-Changes
First actions taken after getting the original source tree; typically
removal of derived or unused common files.

@item TLpatches/patch-...
If any changes are needed to the original sources, record the patches
here so they can be applied next time. Also, send them upstream so
that we don't have to maintain them forever.

@item ChangeLog
Record all TL-specific changes, now and in the future.

@end ftable

@pindex autoreconf@r{, for new program}
After populating the new TL source directory (@file{.../newprog/}, in
the above), run GNU @code{autoreconf} there (@pxref{Build system
tools}).  Once that works, if you are the one who's eventually going
to commit the new package, @code{svn add} the necessary files,
including the generated @file{Makefile.in aclocal.m4 configure}, and
@code{svn:ignore} the Automake cache @file{autom4te.cache}.  (This is
so people checking out the TL source tree do not have to run any
autotools, but can simply run @code{configure}.)

To reiterate: do not fail to commit the generated @file{configure} and
other files. The m4 code in @file{kpse-pkgs.m4} uses the existence of
@file{configure} to determine whether to descend into (and configure)
a given subdirectory.

@pindex reautoconf@r{, for new program}
Then, run the TL tool @code{reautoconf} in the top-level TL
@code{Build/source/} directory, to incorporate the new program into
the build tree. It is good to then rebuild the whole tree (e.g., using
TL's @file{Build/Build} script) to get all the necessary files generated.

It will probably fail.  So then you need to keep at it until the
program compiles and tests successfully.  The most efficient way is to
rerun @code{autoreconf} as needed in the new source directory
(@code{Build/source/.../newprog}), then @code{make} in the
corresponding build directory (@code{Build/work/.../newprog}), then
@code{make check}, etc. In the end, also make sure that the whole tree
builds from scratch.

After final success, don't forget to commit. (Or email the TL
maintainers with the patch.)

@node Adding a new engine
@subsection Adding a new engine

@cindex adding a new engine
@cindex engine, adding new

Adding a new @TeX{} engine is not completely different from adding a
program, but it's not all that similar, either.  In this case, the main
work is done by creating a new subdirectory of @file{texk/web2c/} for
the engine.  The subdirectory is conventionally named ending in
@file{dir}, like @file{pdftexdir} and @file{xetexdir}, to avoid
clashes with executable names.

The source files for the new engine should be put in this
@file{@var{newengine}dir} subdirectory.  Also, a file
@file{@var{newengine}dir/am/@var{newengine}.am} (e.g.,
@file{pdftexdir/am/pdftex.am} is needed with the Makefile fragment
needed to build it.

The overall @file{web2c/Makefile.am} needs to have an @file{include}
statement added to insert that @file{@var{newengine}.am} file.

In @file{web2c/ac/web2c.ac}, a line needs to be added in the
definition of the @code{kpse_tex_progs} variable to include it in the
build.  That line specifies whether the new engine is built by default,
and the additional libraries requires.

For examples of building engines in CWEB, you can check the existing
@file{hitexdir} and @file{mplibdir} directories; these are somewhat
simpler than Lua@TeX{}.  Of course, every engine will have its own
unique features and requirements, so existing examples will only take
you so far.

Web2c is built as one ``package'', with each subdirectory's @file{.am}
fragment inserted with an Automake @code{include}.  This means that,
for instance, @code{$(srcdir)} is @file{.../web2c}, not
@file{.../webdir/enginedir}.  It is a difficult setup to come to terms
with, but the alternative is to recurse into each engine subdirectory,
and that would be far worse (@pxref{Directories,,, automake, GNU
Automake}).

@node Adding a new generic library module
@subsection Adding a new generic library module

@cindex adding a new generic library
@cindex generic library module, adding
@cindex library module, generic, adding

@vindex kpse_libs_pkgs
A generic library module in a subdirectory @file{libs/@var{lib}} must
not depend on @TeX{}-specific libraries, by definition.  It is
included by adding its name @file{@var{lib}} to the M4 macro
@code{kpse_libs_pkgs} in @file{m4/kpse-pkgs.m4}---before any other
libraries from the @TL{} tree on which it depends.

@findex KPSE_WITH_LIB
As with program modules, the subdirectory @file{libs/@var{lib}} must
contain the sources and build system for the library (and any
installable support programs) and a fragment @file{ac/withenable.ac}
that contains the M4 macro @code{KPSE_WITH_LIB} defined in
@file{m4/kpse-setup.m4} with @code{@var{lib}} as the mandatory first
argument and two optional arguments: a list of required libraries from
the TL tree, and a list of options: for libraries, currently there is
only one---specify @code{tree} if this library cannot be replaced by a
system version.

@findex KPSE_TRY_LIB
@findex KPSE_TRY_LIBXX
If a system version can be used, a second fragment
@file{ac/@var{lib}.ac} is needed, containing the M4 macro
@code{KPSE_TRY_LIB} (or @code{KPSE_TRY_LIBXX}) with @code{@var{lib}}
as the mandatory first argument and two additional arguments for the
Autoconf macro @code{AC_LANG_PROGRAM} used to compile and link a small
C (or C++) program as sanity check for using the system library.

@vindex KPSE_@var{LIB}_FLAGS
In addition a file @file{m4/kpse-@var{lib}-flags} (at the top level)
must define the M4 macro @code{KPSE_@var{LIB}_FLAGS} (all uppercase)
setting up the @code{make} variables @code{@var{LIB}_INCLUDES},
@code{@var{LIB}_LIBS}, @code{@var{LIB}_DEPEND}, and
@code{@var{LIB}_RULE} with the values required for @code{CPPFLAGS},
@code{LDADD}, dependencies, and a (multi-line) @code{make} rule to
rebuild the library when necessary.  All of that is needed for the
library from the TL tree and, if supported, for a system version.

@vindex --with-system-@var{lib}
@vindex KPSE_@var{LIB}_SYSTEM_FLAGS
@vindex KPSE_ALL_SYSTEM_FLAGS
If a system library is allowed, @code{KPSE_@var{LIB}_FLAGS} also
provides the configure option @code{--with-system-@var{lib}} and uses
the additional M4 macro @code{KPSE_@var{LIB}_SYSTEM_FLAGS} to generate
the @code{make} variables for a system library.  In addition, the
definition of the M4 macro @code{KPSE_ALL_SYSTEM_FLAGS} in
@file{m4/kpse-pkgs.m4} must be extended by the line:@*@ @ @
@code{AC_REQUIRE([KPSE_@var{LIB}_SYSTEM_FLAGS])}

@node Adding a new @TeX{}-specific library module
@subsection Adding a new @TeX{}-specific library module

@cindex adding a new @TeX{}-specific library
@cindex @TeX{}-specific library module, adding
@cindex library module, @TeX{}-specific, adding

A @TeX{}-specific library module in a subdirectory
@file{texk/@var{lib}} may depend on other @TeX{}-specific libraries
but must not depend on any generic library from the TL tree.  It is
included in the same general ways as a generic library (see the
previous section), with these modifications:

@itemize @bullet
@item
@vindex kpse_texlibs_pkgs
The library name @code{@var{lib}} is added to the M4 macro
@code{kpse_texlibs_pkgs}, which is also in @file{m4/kpse-pkgs.m4}.

@item
@findex KPSE_WITH_TEXLIB
The fragment @code{ac/withenable.ac} must use @code{KPSE_WITH_TEXLIB}.
@end itemize

@node Configure options
@chapter Configure options

@cindex @code{configure} options

Corresponding to the large number of program and library modules there
are a large number @code{configure} options, most of which are
described here.  The command@*@ @ @ @code{configure --help}@*at the
top level gives an exhaustive list of all global options and a few
important module-specific ones, whereas, e.g.,@*@ @ @
@code{texk/lcdf-typetools/configure --help}@* also displays the
@code{lcdf-typetools} specific options, which are not shown at the
top level.

@cindex environment variables, for @code{configure}
The help text also mentions several influential environment variables,
but for @TL{} it is better to specify them as assignments on the
command line.

The @file{./Build} script used to make the binaries shipped with @TL{}
invokes the top-level @code{configure} with a few additional options
(@pxref{Building}).  The defaults discussed below are those for the
actual @code{configure} script; invoking @code{configure} via
@file{./Build} yields different results.

Defaults for most options are set at the top level and propagated
explicitly to all subdirectories.  Options specified on the command
line are checked for consistency but never modified.

@menu
* Global configure options::
* Program-specific configure options::
* Library-specific configure options::
* Variables for configure::
@end menu

@node Global configure options
@section Global configure options

@cindex global @code{configure} options
@cindex @code{configure} options, global
Here are the global configure options.

@menu
* @code{--disable-native-texlive-build}::
* @code{--prefix} @code{--bindir} @dots{}::
* @code{--disable-largefile}::
* @code{--disable-missing}::
* @code{--enable-compiler-warnings=}@var{level}::
* @code{--enable-cxx-runtime-hack}::
* @code{--enable-maintainer-mode}::
* @code{--enable-multiplatform}::
* @code{--enable-shared}::
* @code{--enable-silent-rules}::
* @code{--without-ln-s}::
* @code{--without-x}::
@end menu

@node @code{--disable-native-texlive-build}
@subsection @code{--disable-native-texlive-build}

@vindex --disable-native-texlive-build
If enabled (the default), build for a TL binary distribution as
shipped by the @TeX{} user groups.  This requires GNU @code{make} and
implies @code{--enable-multiplatform} and
@code{--enable-cxx-runtime-hack} (unless they are explicitly disabled),
and enforces @code{--disable-shared}.

If building TL for a GNU/Linux or other distribution, this should be
disabled and system versions of most libraries should be used
(@pxref{Distro builds}).

@vindex --enable-texlive-build
A related option, @code{--enable-texlive-build}, is automatically
passed to all subdirectories (and cannot be disabled).  Subdirectories
that can also be built independently from the TL tree (such as
@file{utils/xindy} and @file{texk/dvipng}) but cooperate with TL can
use this option to enable TL-specific adaptations, such as
installation paths.

@node @code{--prefix} @code{--bindir} @dots{}
@subsection @code{--prefix}, @code{--bindir}, @dots{}

@vindex --prefix configure @r{option}
@vindex --bindir configure @r{option}
These standard Autoconf options specify various installation
directories as usual.  For the complete list, @pxref{Installation
directories}.

@vindex DESTDIR
Also as usual, all values are prefixed by the value of @code{DESTDIR},
if set, on the @code{make} command line (@pxref{Staged Installs, ,
Installation in a temporary location, automake, GNU Automake}).

@node @code{--disable-largefile}
@subsection @code{--disable-largefile}

@vindex --disable-largefile
@cindex large file support
@cindex LFS (large file support)
Omit large file support (LFS), which is needed on most 32-bit Unix
systems for files with 2GB or more.  Regardless of this option, the
size of @code{DVI} and @code{GF} files must always be @math{<2}GB, due
to the file format specifications.

@cindex size of PDF and PS files
@cindex PDF files, size of
@cindex PostScript files, size of
With LFS, there is no fixed limit on the size of PDF files created by
@file{pdftex} or PostScript files created by @file{dvips}.

@node @code{--disable-missing}
@subsection @code{--disable-missing}

@vindex --disable-missing
Immediately terminate the build process if a requested program or feature
must be disabled, e.g., due to missing libraries.  This can help when
figuring out a specific (sub)set of modules to enable.

@node @code{--enable-compiler-warnings=}@var{level}
@subsection @code{--enable-compiler-warnings=}@var{level}

@vindex --enable-compiler-warnings=@var{level}
Enable various levels of compiler warnings for C, C++, and/or
Objective@tie{}C: the @var{level} value can be one of: @code{no min
yes max all}.  The default is @code{yes} in @code{maintainer-mode}
(see below) and @code{min} otherwise.  This option defines the
variables @code{WARNING_[OBJ]C[XX]FLAGS}, but these variables are not
consistently used in all library and program modules.  At present,
these warning flags assume options from the GNU compilers.

@node @code{--enable-cxx-runtime-hack}
@subsection @code{--enable-cxx-runtime-hack}

If enabled (as it is for the native TL build), when using @code{g++},
try to statically link with @code{libstdc++}, thus improving
portability of the resulting binary.  @xref{Macros for compilers}.

@node @code{--enable-maintainer-mode}
@subsection @code{--enable-maintainer-mode}

@vindex --enable-maintainer-mode
Enable @file{make} rules and dependencies not useful (and sometimes
confusing) to the casual user.  This requires current versions of the
GNU build tools (@pxref{Build system tools}), as it automatically
rebuilds infrastructure files as needed.  @xref{maintainer-mode,,
@code{missing} and @code{AM_MAINTAINER_MODE}, automake, GNU Automake}.

@node @code{--enable-multiplatform}
@subsection @code{--enable-multiplatform}

@vindex --enable-multiplatform
@vindex exec_prefix
@vindex --bindir configure @r{option}
@vindex --libdir configure @r{option}
If enabled (as it is for the native TL build) and
@code{--bindir=@var{dir}} or @code{--libdir=@var{dir}} are not
specified, install executables and libraries in per-platform
subdirectories of @file{@var{eprefix}/bin} and
@file{@var{eprefix}/lib} where @var{eprefix} is the value given or
implied for @code{exec_prefix}.  In any case, the values for
@code{bindir} and @code{libdir} are automatically propagated to all
subdirectories.

@node @code{--enable-shared}
@subsection @code{--enable-shared}

@vindex --enable-shared
Build shared versions of the @TeX{}-specific libraries such as
@file{libkpathsea}.  This is not allowed for a native TL build (i.e.,
@code{--disable-native-texlive-build} must also be specified).

@node @code{--enable-silent-rules}
@subsection @code{--enable-silent-rules}

@vindex --enable-silent-rules
@cindex @code{make} rules, verbose vs.@: silent
Enable the use of less verbose build rules.  When using GNU
@code{make} (or any @code{make} implementation supporting nested
variable expansions), you can specify @code{V=1} on the @code{make}
command line to get more verbosity, or @code{V=0} to get less,
regardless of this option.

@node @code{--without-ln-s}
@subsection @code{--without-ln-s}

@vindex --without-ln-s
Required when using a system without a working @code{ln -s} to build
binaries for a Unix-like system.  However, @code{make install} will
not create anything useful, and might fail.

@node @code{--without-x}
@subsection @code{--without-x}

@vindex --without-x
Disable all programs using the X Window System.

@node Program-specific configure options
@section Program-specific configure options

@cindex program-specific @code{configure} options
@cindex @code{configure} options, program-specific
Here are (some of) the program-specific @code{configure} options.

@menu
* @code{--enable-@var{prog}} @code{--disable-@var{prog}}::
* @code{--disable-all-pkgs}::
* Configure options for @file{texk/web2c}::
* Configure options for @file{texk/bibtex-x}::
* Configure options for @file{texk/dvipdfm-x}::
* Configure options for @file{texk/dvisvgm}::
* Configure options for @file{texk/texlive}::
* Configure options for @file{texk/xdvik}::
* Configure options for @file{utils/xindy}::
@end menu

@node @code{--enable-@var{prog}} @code{--disable-@var{prog}}
@subsection @code{--enable-@var{prog}}, @code{--disable-@var{prog}}

@vindex --enable-@var{prog}
@vindex --disable-@var{prog}
Do or do not build and install the program(s) of module @code{@var{prog}}.

@node @code{--disable-all-pkgs}
@subsection @code{--disable-all-pkgs}

@vindex --disable-all-pkgs
Do not build any program modules by default---only those explicitly
enabled.  This is useful when one wants to work on only a single
program, which is specified with an additional @code{--enable} option,
e.g., @code{--enable-dvipdfm-x}.  It's still simplest to check out and
configure the whole source tree, but at least only the program you are
interested in, and its dependencies, are built.  @xref{Build one package}.

Without this option, all modules are built except those that are
explicitly disabled or specify @code{disable} in their
@file{ac/withenable.ac} fragment.

@node Configure options for @file{texk/web2c}
@subsection Configure options for @file{texk/web2c}

@cindex @code{configure} options, for @code{web2c}

@vindex --with-banner-add=@var{str}
@noindent @code{--with-banner-add=@var{str}}@*Add @code{@var{str}} to the
default version string (which is `@code{TeX Live @var{year}}' or
`@code{Web2C @var{year}}') appended to banner lines.  This is ignored
for a native TL build, but distro builds should specify, e.g.,
@code{/@var{SomeDistro}}.

@vindex --with-editor=@var{cmd}
@noindent @code{--with-editor=@var{cmd}}@*Specify the command
@code{@var{cmd}} to invoke from the @code{e} option of @TeX{} and friends,
replacing the default @code{vi +%d '%s'} for Unix or @code{texworks
--position=%d "%s"} for Windows.

@vindex --with-fontconfig-includes=@var{dir}
@vindex --with-fontconfig-libdir=@var{dir}
@noindent @code{--with-fontconfig-includes=@var{dir}},
@code{--with-fontconfig-libdir=@var{dir}}@*Building Xe@TeX{} on
non-Mac systems requires the @code{fontconfig} library headers and
code.  If one or both of these options are given, the required flags
are derived from them; otherwise, they are determined via
@file{pkg-config} (if present).

@cindex X toolkit
@pindex libXt
@pindex Xlib
@noindent @code{--with-mf-x-toolkit}@*Use the X toolkit (@file{libXt}) for
Metafont (the default is to use the lowest-level @file{Xlib} support;
it seems this has the best chance of working across X installations
nowadays).

@vindex --disable-dump-share
@cindex LittleEndian architectures
@noindent @code{--disable-dump-share}@*Make the @code{fmt}/@code{base}
dump files architecture dependent (somewhat faster on LittleEndian
architectures).

@vindex --disable-ipc
@cindex interprocess communication
@noindent @code{--disable-ipc}@*Disable @TeX{}'s @code{--ipc} option.

@vindex --disable-mf-nowin
@pindex mf-nowin
@noindent @code{--disable-mf-nowin}@*Do not build a separate
non-graphically-capable Metafont (@file{mf-nowin}).

@vindex --disable-tex
@vindex --enable-etex
@pindex web2c.ac
@noindent @code{--disable-tex}, @code{--enable-etex}, @dots{}@*Do not or
do build the various @TeX{}, Metafont, and MetaPost engines (defaults are
defined in the fragment @file{texk/web2c/ac/web2c.ac}).

@vindex --disable-web-progs
@noindent @code{--disable-web-progs}@*Do not build the original WEB programs
@file{bibtex}, @dots{}, @file{weave}.  Useful if, e.g., you only want
to (re)build some engines.

@vindex --enable-auto-core
@cindex preloaded binaries
@noindent @code{--enable-auto-core}@*This option causes @TeX{} and Metafont
to produce a core dump when a particular hacky filename is
encountered, for use in creating preloaded binaries.  This is rarely
done nowadays.

@vindex --enable-libtool-hack
@pindex libtool@r{, hack for avoiding excessive linking}
@pindex libfontconfig@r{, hack for avoiding linking dependencies}
@pindex libexpat@r{, dependency of @code{libfontconfig}}
@noindent @code{--enable-libtool-hack}@*
If enabled (which is the default for all platforms), prevents
@code{libtool} from linking explicitly with dependencies of
@file{libfontconfig} such as @file{libexpat}.

@vindex --enable-*win @r{for Metafont window support}
@noindent @code{--enable-*win}@*Include various types of non-X window
support for Metafont (EPSF output, @code{mftalk}, old graphics
terminals, @dots{}).

@vindex --enable-tex-synctex
@vindex --disable-etex-synctex
@cindex synctex
@noindent @code{--enable-tex-synctex}, @code{--disable-etex-synctex},
@dots{}@*Build the @TeX{} engines with or without @code{SyncTeX}
support; ignored for a native @TL{} build.  Defaults are defined in
@file{texk/web2c/ac/web2c.ac}.

@vindex --disable-synctex
@cindex synctex
@noindent @code{--disable-synctex}
@*Do not build the @code{SyncTeX} library and tool.

@node Configure options for @file{texk/bibtex-x}
@subsection Configure options for @file{texk/bibtex-x}

@cindex @code{configure} options, for @code{bibtex-x}
@pindex bibtex8
@pindex bibtexu
@pindex bibtex-x
The programs @code{bibtex8} and @code{bibtexu} have been merged into the
module @code{bibtex-x} (extended Bib@TeX{}).

@vindex --disable-bibtex8
@noindent @code{--disable-bibtex8}@*Do not build the @file{bibtex8} program.

@vindex --disable-bibtexu
@noindent @code{--disable-bibtexu}@*Do not build the @file{bibtexu} program
(building @file{bibtexu} requires @code{ICU} libraries).

@node Configure options for @file{texk/dvipdfm-x}
@subsection Configure options for @file{texk/dvipdfm-x}

@cindex @code{configure} options, for @code{dvipdfm-x}
@pindex dvipdfm-x
@pindex dvipdfmx
@pindex xdvipdfmx

The former modules @code{dvipdfmx} (extended DVI to PDF converter) and
@code{xdvipdfmx} (the same, as used by Xe@TeX{}) have been merged into
@code{dvipdfm-x} at the source level.  Two separate binaries are still
created by default.  In addition, @file{dvipdfm} is created as a
symlink to @file{dvipdfmx}, with backward-compatible (very slightly
different) behavior.

@vindex --disable-dvipdfmx
@noindent @code{--disable-dvipdfmx}@*Do not build the @file{dvipdfmx}
program or make the @file{dvipdfm} symlink.

@vindex --disable-xdvipdfmx
@noindent @code{--disable-xdvipdfmx}@*Do not build the @file{xdvipdfmx}
program.

@node Configure options for @file{texk/dvisvgm}
@subsection Configure options for @file{texk/dvisvgm}

@cindex @code{configure} options, for @file{dvisvgm}
@pindex dvisvgm

@vindex --with-system-libgs
@noindent @code{--with-system-libgs}@*Build @file{dvisvgm} using installed
Ghostscript (@code{gs}) headers and library (not allowed for a native
TL build).  The default is to load the @code{gs} library at runtime if
possible, else to disable support for PostScript specials.

@vindex --without-libgs
@noindent @code{--without-libgs}@*Build @file{dvisvgm} without PostScript
support at all.  Because the dynamic loading just mentioned defeats all
attempts at static linking, the result can crash due to library
incompatibilities, e.g., on CentOS 5.

@vindex --with-libgs-includes@r{,} -libdir
@noindent @code{--with-libgs-includes=@var{dir}},
@code{--with-libgs-libdir=@var{dir}}@*Specify non-standard locations
of the Ghostscript headers and library.

@node Configure options for @file{texk/texlive}
@subsection Configure options for @file{texk/texlive}

@cindex @code{configure} options, for @file{texk/texlive}
@vindex --disable-linked-scripts
@noindent @code{--disable-linked-scripts}@*Do not install the ``linked
scripts'' (@pxref{Linked scripts}), except for the TL scripts required
to run @code{texlinks}.

@node Configure options for @file{texk/xdvik}
@subsection Configure options for @file{texk/xdvik}

@cindex @code{configure} options, for @file{xdvik}
@pindex xdvik

@vindex --with-gs=@var{filename}
@cindex Ghostscript location for Xdvik
@noindent @code{--with-gs=@var{filename}}@*Hardwire the location of Ghostscript
(@file{gs}) as called by Xdvik.

@vindex --with-xdvi-x-toolkit=@var{kit}
@pindex motif
@pindex xaw
@noindent @code{--with-xdvi-x-toolkit=@var{kit}}@*Use toolkit
@code{@var{kit}} for @file{xdvik}, one of: @code{motif xaw xaw3d
neXtaw}.  The default is @code{motif} if available, else @code{xaw}.

@vindex --enable-xi2-scrolling
@pindex XInput
@pindex scrolling, smooth
@noindent @code{--enable-xi2-scrolling}@*Use XInput 2.1 ``smooth scrolling''
if available (default: yes, except for a native TL build).

@node Configure options for @file{utils/xindy}
@subsection Configure options for @file{utils/xindy}

@cindex @code{configure} options, for @file{xindy}
@pindex xindy

@vindex --enable-xindy-rules
@noindent @code{--enable-xindy-rules}@*Build and install @code{xindy} rules
(default: yes, except for a native TL build).

@vindex --enable-xindy-docs
@noindent @code{--enable-xindy-docs}@*Build and install @code{xindy}
documentation (default: yes, except for a native TL build).

@vindex --with-clisp-runtime=@var{filename}
@pindex lisp.run@r{,} lisp.exe
@cindex CLISP
@noindent @code{--with-clisp-runtime=@var{filename}}@*Specifies the
full path for the Clisp runtime file (@file{lisp.run} or
@file{lisp.exe}) to be installed.  When specified as @code{default}
(the default for a native TL build) the path is determined by the
Clisp executable; the value @code{system} (not allowed for a native TL
build, but the default otherwise) indicates that @file{xindy} will use
the installed version of @file{clisp} (which must be identical to the
one used to build @file{xindy}).

@node Library-specific configure options
@section Library-specific configure options

@cindex library-specific @code{configure} options
@cindex @code{configure} options, library-specific
Here are (some of) the library-specific @code{configure} options,
starting with this generic one:

@vindex --with-system-@var{lib}
@noindent @code{--with-system-@var{lib}}

Use an installed (system) version of the library @code{@var{lib}};
this option exists for most libraries, but is not allowed for a native
TL build.  Using a system version implies also using the system
versions of all libraries that @var{lib} depends on.

@vindex --with-@var{lib}-includes=@var{dir}@r{,} -libdir
For many libraries @code{--with-@var{lib}-includes=@var{dir}} and
@code{--with-@var{lib}-libdir=@var{dir}} can specify non-standard
search locations; others use @file{pkg-config} or similar to determine
the required flags.

The top-level @file{configure} script performs a consistency check for all
required system libraries and bails out if tests fail.

@menu
* Configure options for @code{kpathsea}::
@end menu

@node Configure options for @code{kpathsea}
@subsection Configure options for @code{kpathsea}

@cindex @code{configure} options, for @code{kpathsea}

@noindent @code{--enable-@var{cmd}-default},
@code{--disable-@var{cmd}-default}@*Determine the compile time default
for whether or not to run @var{cmd}, which is one of:
@table @code
@item mkocp
(Omega compiled translation process file)
@item mkofm
(Omega font metrics file)
@item mktexfmt
(format/base dump file)
@item mktexmf
(Metafont source)
@item mktexpk
(PK bitmap font)
@item mktextex
(@TeX{} source)
@item mktextfm
(TFM file)
@end table

@noindent to generate the specified type of file dynamically.
The default can be overridden by the user in any case
(@pxref{@code{kpathsea} library}).

@node Variables for configure
@section Variables for configure

@cindex variables for @code{configure}
@cindex @code{configure} variables

The values for these variables can be specified as @code{configure}
arguments of the form @code{@var{VAR}=@var{value}}.  They can also be
defined in the environment, but that might not work for cross
compilations.

@vtable @code
@item CC
@itemx CXX
@itemx CPPFLAGS
And plenty more.  As usual with Autoconf, these variables specify the
name (or full path) of compilers, preprocessor flags, and similar.
@xref{Preset Output Variables,,, autoconf, GNU Autoconf}.

@item CLISP
@pindex clisp
Name (or full path) of the @file{clisp} executable, used to build
@code{xindy}.

@item FT2_CONFIG
@itemx ICU_CONFIG
@itemx PKG_CONFIG
@pindex freetype-config
@pindex icu-config
@pindex libfreetype
@cindex ICU libraries
These specify the name (or path) for the @file{freetype-config},
@file{icu-config}, and @file{pkg-config} commands used to determine the
flags required for system versions of @file{libfreetype}, the ICU
libraries, and other libraries, respectively.

@item KPSEWHICH
@pindex kpsewhich
Name (or path) of an installed @file{kpsewhich} binary, used by
@code{make check} to determine the location of, e.g.,
@file{cmbx10.tfm}.

@item MAKE
@itemx SED
And more. Name (or path) of the @code{make}, @code{sed}, and similar
programs; used at the top level and propagated to all subdirectories.

@item PERL
@itemx LATEX
@itemx PDFLATEX
Name (or full path) for the @file{perl}, @file{latex}, and @file{pdflatex}
commands used, e.g., to build the @code{xindy} documentation.

@end vtable

@node Coding conventions
@chapter Coding conventions

@cindex coding conventions
@cindex conventions, coding

Ideally, building all of @TL{} with
@code{--enable-compiler-warnings=max} should produce no (GCC) compiler
warnings at all.  In spite of considerable efforts into that direction
we are still far from that goal and there are reasons that we may
never fully reach it.  Below are some rules about declarations of
functions or variables and the use of @code{const}.  These rules
should be applied to the code maintained in the @TL{} tree and for
other packages whose maintainers are willing to accept patches.

@menu
* Declarations and definitions::
* Const::
@end menu

@node Declarations and definitions
@section Declarations and definitions

@cindex declarations and definitions, in source code
@cindex source code declarations
@cindex ANSI C
@cindex declarations before statements, avoiding
@cindex C, ANSI, required
@cindex C99, avoided

@subsubheading C standards

The @TL{} build system no longer supports pre-ANSI C compilers.  Thus
all function prototypes and definitions must conform to the ANSI C
standard (including @code{void} in the declaration of C functions with
no parameters).  On the other hand, TL is built for a wide variety of
systems, not all of which support the C99 standard.  Therefore using
C99 features should be avoided if that can easily be done.  In
particular, C code must not contain declarations after statements or
C++-style comments.

@pindex chktex
@findex stpcpy
If some C99 (or later) constructs must be used, the module should
verify that they are available and otherwise provide an alternative.
For example, the module @file{texk/chktex} uses the C99 function
@code{stpcpy()} that may or may not be available on a particular
system.  It uses @code{AC_CHECK_DECLS([stpcpy])} in
@file{configure.ac} to test this, and provides a perhaps
less efficient alternative (in the file @file{Utility.h}):

@example
#if !(defined HAVE_DECL_STPCPY && HAVE_DECL_STPCPY)
static inline char *stpcpy(char *dest, const char *src)
@{
  return strcpy(dest, src) + strlen(src);
@}
#endif
@end example

@subsubheading Static functions

@cindex @code{static} functions
Functions used in only one file should be declared @code{static}; they
require no prototype except in forward declarations.

@subsubheading Extern functions

@cindex @code{extern} functions
Functions not declared @code{static}, usually because they are used in
several files, require an (@code{extern}) prototype in exactly one
header file, which is included in the file defining the function and
in all files using that function---this is the only way to guarantee
consistency between definition and use.  There should be no
@code{extern} declarations sprinkled throughout the C code (with or
without comments as to where that function is defined).

@subsubheading Variable declarations

@cindex variable declarations, in source code
The declaration of global variables follows analogous rules: they are
either declared @code{static} if used in only one file or declared
@code{extern} in exactly one header and instantiated in exactly one
file.

@node Const
@section Const

@cindex @code{const}

The @code{const} feature of C is valuable, but easy to mis-use.

@subsubheading Function parameters

Ideally, a function parameter not modified by the function should be
declared as @code{const}.  This is important in particular for strings
(@code{char*}) because the actual arguments are often string literals.
It is perfectly legitimate and safe to use a type @code{char*} value
for a type @code{const char*} variable (in an assignment, as
initializer, as function argument, or as return value).  It is equally
safe to use a type @code{char**} value for a type @code{const
char*const*} variable, but not for a type @code{const char**} variable
since that might cause modification of a quantity supposed to be
constant.

@cindex X11 headers, and @code{const}
@cindex @code{libfreetype}, and @code{const}
Getting all @code{const} qualifiers right can get quite involved but
can almost always be done.  There are only a couple notable
exceptions: the X11 headers are full of declarations that ought to use
@code{const} but do not; at one time, @file{libfreetype} also did not
fully specify @code{const}, but this has not been checked recently.

@subsubheading What must be avoided with @code{const}

@cindex warning, discards qualifiers
@cindex discards qualifiers warning
The GCC compiler warnings ``assignment discards qualifiers@dots{}''
and analogous warnings for ``initialization'', ``passing arg'', or
``return'' must be strenuously avoided in our own code.  The only
exception is when they are caused by X11 declarations or other third
party code.

@subsubheading What should be avoided with @code{const}

@cindex type cast from const, avoiding
A type cast, e.g., from @code{const char*} to @code{char*} does not
solve any problems; depending on warning options, it may only hide
them.  Therefore such casts should be avoided whenever possible and
otherwise must be carefully analyzed to make sure that they cannot
cause the modification of quantities supposed to be constant.

@node Continuous integration
@chapter Continuous integration

@cindex continuous integration
@cindex Travis-CI

The @TL{} sources are subjected to continuous integration testing on
Travis-CI (@url{https://travis-ci.org/TeX-Live/texlive-source}) via a
git-svn mirror of the sources that is pushed to Github
(@url{https://github.com/TeX-Live/texlive-source}). The git-svn mirror
is updated (currently) at 30 minute intervals, and only the last
commit pushed is tested on Travis-CI.

@menu
* Transfer from Subversion to Github::
* Automatic update of the Git mirror::
* CI testing on Travis-CI::
* Releases on Github::
@end menu

@node Transfer from Subversion to Github
@section Transfer from Subversion to Github

@pindex git-svn
The git-svn program (@url{https://git-scm.com/docs/git-svn}) is used
to check out the subtree @code{Build/source} of the canonical
Subversion repository.  The author index file used is not maintained
in either Git or Subversion but can be provided on request.

@c TODO what should we do here with the author index file? It contains a
@c mapping from subversion names to name/email as shown in git.

The initial checkout was done by invoking
@example
git svn --authors-file usermap clone \
  svn://@var{user}@@tug.org/texlive/trunk/Build/source
@end example

@noindent where the @code{usermap} file maps Subversion user names to
name and emails of the authors.  Anonymous checkout is also possible:
@example
git svn --authors-file usermap clone \
  svn://tug.org/texlive/trunk/Build/source
@end example

In the following, we will use @emph{admin} to refer to a user who has
read/write access to the @TL{} subversion repository, and is also an
administrator of the `@code{TeX-Live}' team at Github. The above
initial checkout has been carried out by @emph{admin} on the server
@code{texlive.info}.

On Github, a new git repository named @code{texlive-source} was
created by @emph{admin} within the @code{TeX-Live} ``organization''
(@url{https://github.com/TeX-Live}).  The remote was added to the
checkout with @code{git remote add origin
git@@github.com:TeX-Live/texlive-source.git}.

To automate the update on Github, a new ssh key was generated and
added to the @code{texlive-source} repository on Github as deployment
key. Thus, pushes using this key can only go to the
@code{texlive-source} repository and not anywhere else.

The usage of @code{git-svn} requires a strict discipline to keep a
linear history in the master branch. Since we are aiming at a pure
mirror facility on Github, we have decided to further restrict the
@code{master} branch of the @code{texlive-source} repository on Github
to changes by @emph{admin}.

This setup allows other developers to branch off @code{master} and
push their branches to the Github repository, but all updates need to
come from the local @code{master} (not the one on Github) to
Subversion, back to @code{master} on @code{texlive.info}, and from
there to Github.

@node Automatic update of the Git mirror
@section Automatic update of the Git mirror

@emph{admin} has installed a cron job on @code{texlive.info} running
every 30 minute which essentially runs @code{git svn rebase} and
@code{git push} in the @code{master} branch of the checkout. The first
command fetches the changes from the Subversion repository and updates
the @code{master} branch with them, and the second pushes changes (if
any) to Github.

@node CI testing on Travis-CI
@section CI testing on Travis-CI

@pindex travis.yml
The @code{source} tree of @TL{} contains a top-level file
@code{.travis.yml} which controls the automatic testing on
Travis-CI. @emph{admin} has registered with Travis-CI and allowed
access to the Github's @code{TeX-Live} organization's
@code{texlive-source} repository. The default settings are to build
the last commit of each push. No further action is necessary on
Travis-CI.

If changes have been pushed via the cron job above, Travis-CI will
automatically checkout the last pushed commit and try building it.

@node Releases on Github
@section Releases on Github

Given a git checkout of @code{texlive-source}:

@example
git pull
git tag build-svnNNNN
git push --tags
@end example

@noindent and the result will appear at
@url{https://github.com/TeX-Live/texlive-source/releases}.
Releases can also be made manually from that web page (see
@code{tl-update-bindir} for hints).

@c made from pod doc.
@include tlbuild-incl/install-tl.texi
@include tlbuild-incl/tlmgr.texi

@node Index
@unnumbered Index

@printindex cp

@bye