@ifnottex @macro eTeX e-@TeX{} @end macro @end ifnottex @node Build System @chapter The @TL{} Build System @cindex build system @cindex the @TL{} build system The @TL{} build system has been redesigned in 2009, using Autoconf, Automake, and Libtool. Thus @* @ @ @ @code{configure && make && make check && make install} @* or the more or less equivalent top-level @code{Build} script suffice to build and install the @TL{} programs, where @code{make check} performs various test of the generated programs that are not necessary but strongly recommend. The main components of the @TL{} build system are @TeX{} specific programs in subdirectories @file{texk/@var{prog}}, utility programs in subdirectories @file{utils/@var{prog}}, @TeX{} specific libraries in subdirectories @file{texk/@var{lib}} (@code{@var{lib}=kpathsea}@dots{}) used by the @TeX{} specific programs, and generic libraries in subdirectories @file{libs/@var{lib}}. The primary design goal 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, configure options to be seen at the top-level, and more. An explicit list of all available modules is only kept in one central place. A second, related goal is to configure and build each library before configuring any other (program or library) module using that library. This allows to check 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 (parts of) the distributed source tree and document any modifications of that source tree. All this should simplify upgrading of modules maintained independently and/or integrating new modules into the @TL{} build system. @menu * Prerequisites:: Requirements to Build @TL{}. * Building and Installing:: Building and Installing @TL{}. * Source Tree:: The @TL{} Source Tree. * Configure Options:: List of all Configure Options. * Cross Compilation:: Cross Compilation. * Coding Rules:: Coding Rules for @TL{}. @end menu @node Prerequisites @section Requirements to Build @TL{} Building the @TL{} programs requires @itemize @bullet @item C and C++ compilers @item GNU @command{make} @end itemize @noindent and uses the libraries included in the @TL{} source tree. There are, however, some additional requirements @itemize @bullet @item @file{xindy} requires GNU @command{clisp} and in addition @command{perl}, @command{latex}, and @command{pdflatex} to build the rules and/or documentation. @item Autodetection of the @TL{} platform name for @file{biber} requires @command{perl}. @item @file{xpdfopen} and @file{xdvik} require X11 headers and libraries (often a ``development'' package, not installed by default). @item XeTeX requires an Objective C++ compiler under Mac OS X or otherwise @file{libfontconfig} (again both headers and library). @item Modification of any @code{.y} or @code{.l} source files requires @file{bison} or @file{flex} to updatete the corresponding C sources; modification of the sources for @code{.info} files requires @command{makeinfo}. @item Modification of any part of the build system (@code{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. @end itemize @noindent Without the required tools modifying such files or building these programs must avoided, e.g., via @code{--disable-xindy} or @code{--without-x}. @node Building and Installing @section Building and Installing @TL{} The top-level @file{Build} script can be used to configure and build everything in a subdirectory (root of the build tree, default @file{Work}), install everything in an other subdirectory (default @file{inst}), and finally run @code{make check}. Several details of this process can be specified via environment variables and a few leading options; all remaining arguments (assignments or options) are passed to the @file{configure} script. Or one can run @command{configure} and @command{make} in a suitable empty subdirectory. Running the top-level @file{configure} script configures just the top-level and the subdirectories @file{libs}, @file{utils}, and @file{texk}. Running @command{make} at the top-level first iterates over all @TeX{} specific libraries, and then runs @command{make} in @file{libs}, @file{utils}, and @file{texk} to iterate over all generic libraries, utility programs, and @TeX{} specific programs. These iterations consist of two steps: @* (1) For each library or program module not yet configured run @command{configure} adding the configure option @code{--disable-build} if the module need not be built or otherwise run @command{make all}. @* (2) For each library or program module that must be built run @command{make} for the selected target(s): @code{default} or @code{all} to (re-)build, @code{check} to run tests, @code{install} etc. Running the top-level @command{make} a second time iterates again over all library and program modules but finds nothing to be done unless some source files have been modified. In case configuring or building a module fails, one could fix the problem, remove the subdirectory for that module from the build tree, and rerun the top-level @command{make} (or @file{Build} script with @code{--no-clean} as additional first argument). With the configure option @code{--disable-all-pkgs} all program and library modules are configured but none of them are built. The @file{Makefile} for each such module contains all build rules and dependencies and can be invoked to build an individual program or library and causes to first build any required libraries. This build "on demand" procedure is used, e.g., in the @code{luatex} repository to build Lua@TeX{}, essentially from a subset of the complete @TL{} tree. Similarly, when, e.g., building @eTeX{} has been disabled (as by default), one can run @command{make etex} (or @command{make etex.exe}) in @file{texk/web2c/} to build @eTeX{} (altough there is no simple way to install @eTeX{}). The @TL{} build system carefully formulates dependencies as well as make rules when a tool (such as @command{tangle}, @command{ctangle}, or @command{convert}) creates several output files. This allows for parallel builds (@command{make -j @var{n}} with @var{n}>1 or even @command{make -j}) that can considerably speed up the @TL{} build on multi core systems. Further speed up can be achieved by using a configure cache file, i.e., with the option @code{-C}. Running @command{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, whereas @command{make dist-check} also verifies that this tarball suffices to build and install all of @TL{}. @subsection Installation Paths 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}}, data (including "linked scripts") in @code{@var{datarootdir}/texmf-dist}, manpages in @code{@var{mandir}}, and @TeX{} info files in @code{@var{infodir}}. The values of these directories are determined by @command{configure} and can be specified explictly 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 and modified as follows: @itemize @bullet @item If the option @code{--enable-multiplatform} is given (or implied for a native @TL{} build), @code{/@var{host}}, i.e., the canonical host name is appended to @code{@var{bindir}} and @code{@var{libdir}}. @item In a native @TL{} build @code{@var{datarootdir}} is set to @code{@var{prefix}}, @code{@var{mandir}} to @code{@var{prefix}/texmf-dist/doc/man}, and @code{@var{infodir}} to @code{@var{prefix}/texmf-dist/doc/info}. @end itemize @noindent The top-level @file{configure} script displays all these installation paths. For a native @TL{} build either for the @TL{} DVD or for an additional platform the contents of @code{@var{bindir}} should be copied to the directory @code{Master/bin/@var{arch}} of the @TL{} tree where @code{@var{arch}} is the @TL{} platform name corresponding to the canonical host name @code{@var{host}}, the contents of @code{@var{libdir}} and @code{@var{includedir}} can be discarded, and everything else should match files already present in the @TL{} tree. @subsection Linked Scripts Quite a few executables are architecture independent Shell, Perl, or other scripts. Some of them are maintained as part of the @TL{} source tree, but most are maintained elsewhere with copies under @file{texk/texlive/linked_scripts}. They are installed under @code{@var{datarootdir}/texmf-dist/scripts}; for Unix-like systems there is a symbolic link pointing, e.g., from @code{@var{bindir}/ps2eps} to @code{@var{datarootdir}/texmf-dist/scripts/ps2eps/ps2eps.pl} whereas for Windows @code{@var{bindir}/ps2eps.exe} is a copy of a small standard binary serving the same purpose. One reason for all this is to avoid having many copies for the same script, but most importantly this allows to invoke the same Perl or other script under Windows. @subsection Distro Builds Although they use the same code base, building for a @TL{} binary distribution as shipped by the user groups may be quite different from a 'distro' build for, e.g., some kind of Linux distribution, a *Bsd or Mac OS X port, or similar. While a @TL{} binary distribution uses shared libraries (@file{libc}, @file{libm}, X11 libraries, and @file{libfontconfig}) only when absolutely necessary, a distro might use as many shared libraries as possible, including @TeX{} specific libraries such as @file{libkpathsea}. In addition the installation paths will, in general, be quite different. @subsubsection Configuring for a Distro For a distro build you must use @* @ @ @ @code{--disable-native-texlive-build} @* and should use @* @ @ @ @code{--with-banner-add=/@var{SomeDistro}} @* to identify your distro. You may specify @* @ @ @ @code{--enable-shared} @* to build shared @TeX{} specific libraries and might add @* @ @ @ @code{--disable-static} @* to not build the static ones. You would like to use @* @ @ @ @code{--with-system-@var{lib}} for as many libraries as possible and may then have to add @code{--with-@var{lib}-includes=@var{dir}} and/or @code{--with-@var{lib}-libdir=@var{dir}}. You should specify @* @ @ @ @code{--prefix=/usr} or perhaps @code{--prefix=/opt/TeXLive} @* and may have to add @* @ @ @ @code{--libdir=\$@{exec_prefix@}/lib64} @* for 64-bit bi-arch (Linux) systems. To make a usable @TeX{} installation, you need (thousands of) support files in addition to the binaries that are built and installed here. The support files are maintained completely independently. The best basis for dealing with them is the @TL{} (plain text) database and/or the @TL{} installer. @node Source Tree @section The @TL{} Source Tree The @TL{} source tree is the subtree rooted at @file{Build/source} of the complete @TL{} tree and contains the sources for all @TL{} executables as well as @command{make} rules to build and install them together with some of their support files. @menu * Top Levels:: The Top-Level Directories. * Autoconf Macros:: @TL{} Specific Autoconf Macros * Library Modules:: Structure of Library Modules. * Program Modules:: Structure of Program Modules. * Extending:: Adding New Modules. @end menu @include build-tools @noindent 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 when some of their sources have been changed. This can be done explicitly with the top-level @command{reautoconf} script or implicitly by using the configure option @code{--enable-maintainer-mode}. The files in the SVN repository @url{svn://tug.org/texlive/trunk} are all up to date, but this need not be reflected by their timestamps. To avoid unnecessary runs of @command{bison}, @command{flex}, or @command{makeinfo} it may be necessary to @command{touch} the generated (@file{.c}, @file{.h}, or @file{.info}) files. With @code{--enable-maintainer-mode} mode it may also be necessary to @command{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 Levels @subsection The Top-Level Directories The files @file{config.guess}, @file{config.sub}, etc.@ for most packages are kept centrally in @file{build-aux/}, sourced from GNU Gnulib (@url{http://www.gnu.org/software/gnulib}), which in turn pulls them from their ultimate upstream source repository. There are, however, independent copies in, e.g., @file{libs/freetype2/freetype-*/builds/unix/}, and similar places. The @command{reautoconf} script does not take care of those, but a @TL{} cron job keeps them in sync (nightly). The directories @file{m4/} and @file{am/} contain Autoconf macros and @file{Makefile.am} fragments respectively, all of them used in many places. The file @file{m4/kpse-pkgs.m4} contains lists of all program and library modules; missing modules are, however, silently ignored. Each such module contributes fragments defining its capabilities and requirements to the @file{configure.ac} scripts at the top-level and in the subdirectiories @file{libs}, @file{utils}, and @file{texk}. The fragments from program modules supply 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 decides 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}. The directory @file{extra/} contains things which are not part of the TeX Live build, but are present for convenience, e.g., @file{epstopdf} developed here or @file{xz} required by the @TL{} installer. @node Autoconf Macros @subsection @TL{} Specific Autoconf Macros @c @ovar(ARG) @c ---------- @c The ARG is an optional argument. To be used for macro arguments in @c their documentation (@defmac). @macro ovar{varname} @r{[}@var{\varname\}@r{]}@c @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). @macro dvar{varname, default} @r{[}@var{\varname\} = @samp{\default\}@r{]}@c @end macro Here we describe Autoconf macros used for several modules. They are supplemented by module specific macros in directories such as @file{texk/dvipng/m4/}. @subsubsection General Setup The macro @code{KPSE_BASIC} is used to initialize the @TL{} infrastructure common to all generic library and utility program modules, whereas the @TeX{} specific library and program modules use @code{KPSE_COMMON} to perform additional checks. @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. @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} @* and check for various frequently used functions, headers, types, and structures. @end defmac @subsubsection Programs @defmac KPSE_CHECK_LATEX Set LATEX to the name of the first of @command{latex}, @command{elatex}, or @command{lambda} existing in the PATH, or to @code{no} if none of them exists. Call @code{AC_SUBST} for LATEX. The result of this test can be overridden by setting the LATEX variable or the cache variable @code{ac_cv_prog_LATEX}. @end defmac @defmac KPSE_CHECK_PDFLATEX Check for @command{pdflatex} existing in the PATH and set PDFLATEX. @end defmac @defmac KPSE_CHECK_PERL Check for @command{perl} or @command{perl5} existing in the PATH and set PERL. @end defmac @defmac KPSE_PROG_LEX Call @code{AC_PROG_LEX} and add the flag @code{-l} for @command{flex}. @end defmac @subsubsection Compilers @defmac KPSE_COMPILER_WARNINGS When using the (Objective) C/C++ compiler set 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 the moment this only works for GNU compilers, but could be extended to others when necessary. 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 VISIBILITY_C[XX]FLAGS to flags to hide external symbols. Call @code{AC_SUBST} for this variable. At the moment this only tests for @code{-fvisibility=hidden}, but that could be extended with more flags when necessary. 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 Provide the configure option @code{--enable-cxx-runtime-hack}. If enabled and when using @command{g++}, try to statically link with @file{libstdc++}, somewhat improving portability. This macro caches its result in the @code{kpse_cv_cxx_hack} variable. @end defmac @subsubsection Library Functions @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 @subsubsection Flags for Libraries and Headers Each library module @file{libs/@var{lib}} or @file{texk/@var{lib}} there is supplemented by a macro @code{KPSE_@var{LIB}_FLAGS} that provides make variables for that library. For, e.g., @file{libs/libpng} there is: @defmac KPSE_LIBPNG_FLAGS Provide the configure option @code{--with-system-libpng}. Set and @code{AC_SUBST} make variables for modules using this library (either an installed version or from the @TL{} tree): LIBPNG_INCLUDES for use in CPPFLAGS, LIBPNG_LIBS for use in LDADD, LIBPNG_DEPEND for use as dependency, and LIBPNG_RULE defining @command{make} rules to rebuild the library. @end defmac @defmac KPSE_ADD_FLAGS (@var{name}) Temporarily extend CPPFLAGS and LIBS with the values required for the library module @code{@var{name}}. @end defmac @defmac KPSE_RESTORE_FLAGS Restore CPPFLAGS and LIBS to their original values. @end defmac @noindent The file @file{configure.ac} for a hypothetical module @file{utils/foo} using @file{libpng} (and @file{zlib}) would contain @* @ @ @ @code{KPSE_ZLIB_FLAGS} @* @ @ @ @code{KPSE_LIBPNG_FLAGS} @* and @file{Makefile.am} might contain @* @ @ @ bin_PROGRAMS = foo @* @ @ @ AM_CPPFLAGS = $@{LIBPNG_INCLUDES@} $@{ZLIB_INCLUDES@} @* @ @ @ foo_LDADD = $@{LIBPNG_LIBS@} $@{ZLIB_LIBS@} @* @ @ @ foo_DEPENDENCIES = $@{LIBPNG_DEPEND@} $@{ZLIB_DEPEND@} @* @ @ @ ## Rebuild libz @* @ @ @ @@ZLIB_RULE@@ @* @ @ @ ## Rebuild libpng @* @ @ @ @@LIBPNG_RULE@@ @noindent In order to examine some @file{libpng} features, @file{configure.ac} should be continued with @* @ @ @ @code{KPSE_ADD_FLAGS([zlib])} @* @ @ @ @code{@dots{} #} tests for @file{zlib} features (if any). @* @ @ @ @code{KPSE_ADD_FLAGS([libpng])} @* @ @ @ @code{@dots{} #} tests for @file{libpng} features. @* @ @ @ @code{KPSE_RESTORE_FLAGS #} restore CPPFLAGS and LIBS. @subsubsection Windows Specific Macros Windows differs in several aspects from Unix-like systems, many of them due to the lack of symbolic links. @defmac KPSE_CHECK_WIN32 Check if compiling for a Windows system. The result is @code{no} for Unix-like systems (including Cygwin), @code{mingw32} for Windows with GCC, or @code{native} for Windows with MSVC and is cached in the @code{kpse_cv_have_win32} variable. @end defmac @defmac KPSE_COND_WIN32 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 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 Call @code{KPSE_COND_WIN32} and define the Automake conditional @code{WIN32_WRAP} (@code{true} if the standard Windows wrapper @file{texk/texlive/w32_wrapper/runscript.exe} exists). This wrapper is used on Windows instead of symlinks to the linked scripts. @end defmac @defmac KPSE_WIN32_CALL Call @code{KPSE_COND_WIN32}, check if the file @file{texk/texlive/w32_wrapper/callexe.c} exists, and if so 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 for Windows instead of a symlink @code{@var{bar}->@var{foo}} for Unix-like systems. @end defmac @node Library Modules @subsection Structure of Library Modules The structure of library modules is best explained with a few examples. @subsubsection The @code{png} Library in @file{libs/libpng} This generic library uses the distributed source tree in, e.g., @file{libpng-1.5.17} with all modifications recorded in @file{libpng-1.5.17-PATCHES/*}. The @file{configure.ac} fragment @file{ac/withenable.ac} contains @example KPSE_WITH_LIB([libpng], [zlib]) @end example @noindent with the module name and indicating the dependency on @code{zlib}. A third argument @code{tree} would specify that the library from the @TL{} tree can not be replaced by a system version. That not being the case, a second fragment @file{ac/libpng.ac} contains @example KPSE_TRY_LIB([libpng], [#include ], [png_structp png; png_voidp io; png_rw_ptr fn; png_set_read_fn(png, io, fn);]) @end example @noindent and provides the simple C code @example #include int main () @{ png_structp png; png_voidp io; png_rw_ptr fn; png_set_read_fn(png, io, fn); return 0; @} @end example @noindent used to verify the usability of a system version. The similar macro @code{KPSE_TRY_LIBXX} would provide some C++ code. These fragments are included by @file{configure.ac} at the top levels. A proxy build system (@file{configure.ac}, @file{Makefile.am}, and @file{include/Makefile.am}) ignores the distributed one and 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/}. The module is supplemented by the file @file{m4/kpse-libpng-flags.m4} that defines the @code{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 dependency, and @code{LIBPNG_RULE} defining @code{make} rules to rebuild the library. In addition @file{m4/kpse-libpng-flags.m4} supplies the configure option @code{--with-system-libpng} and uses @command{pkg-config} to determine the flags required for the system library. @subsubsection The @code{zlib} Library in @file{libs/zlib} This generic library is quite analogous to @code{libpng} but does not depend 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. @subsubsection The @code{freetype} Library in @file{libs/freetype2} This module uses a wrapper build system with an almost trivial @file{configure.ac} and with @file{Makefile.am} that invokes @command{configure} and @command{make} for the distributed source, followed by @command{make install} with the build tree as destination. The flags required for the system library are obtained through @command{freetype-config}. @subsubsection The @code{kpathsea} Library in @file{texk/kpathsea} This is one of the @TeX{} specific libraries that are maintained as part of @TL{}. Other than the generic libraries they are (static and/or shared) Libtool libraries and are installed together with the programs. They are, however, not part of the @TL{} DVD as distributed by @TeX{} user groups. It is possible, although quite unusual to specify the configure option @code{--with-system-kpathsea} in order to use a system version of the library and it may then be necessary to specify @code{--with-kpathsea-includes} and/or @code{--with-kpathsea-libdir}. In addition to @file{ac/withenable.ac} and @file{ac/kpathsea.ac} there is a third fragment @file{ac/mktex.ac} included by both @file{ac/withenable.ac} and @file{configure.ac} that supplies configure options such as @code{--enable-mktextfm-default} determining the compile time default whether or not to run @code{mktextfm} to generate a missing @file{.tfm} file. Note, however, that the command line options @code{-mktex=tfm} or @code{-no-mktex=tfm} for @TeX{}-like engines override this default. @node Program Modules @subsection Structure of Program Modules The structure of program modules is again best explained with a few examples. @subsubsection The @code{t1utils} Package in @file{utils/t1utils} Once again we use the distributed source tree @file{t1utils-1.38} with modifications documented in @file{t1utils-1.38-PATCHES/*} 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}. @subsubsection The @code{xindy} Package in @file{utils/xindy} This module uses the distributed source tree @file{xindy-2.4} with modifications documented in @file{xindy-2.4-PATCHES/*}, a proxy @file{configure.ac}, and a wrapper @file{Makefile.am} that descends into @file{xindy-2.4}. This requires that the distributed @file{Makefile}s allow a VPATH build, can handle all targets, and do not refer to @code{$@{top_srcdir@}} or @code{$@{top_builddir@}}. The fragment @code{ac/withenable.ac} contains @example KPSE_ENABLE_PROG([xindy], , [disable native]) 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 @code{--enable-xindy} (because it requires @code{clisp}) and @code{native} disallows cross compilation. The additional fragments @file{ac/xindy.ac} and @file{ac/clisp.ac} specify more configure options to be seen at the top-leved with @file{ac/xindy.ac} also included by @file{configure.ac}. @subsubsection The @code{xdvik} Package in @file{texk/xdvik} This package is maintained as part of the @TL{} tree with sources in its top-level and the subdirectory @file{gui}. The fragment @code{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 @noindent and specifies the dependency on the @code{kpathsea}, @code{freetype}, and @code{X11} libraries. The @code{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 and in a cross compilation they differ. 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. @subsubsection The Subdirectory @file{utils/asymptote} This subdirectory contains the sources for @file{asy} and @file{xasy} but due to its complexity and prerequisites (e.g., @file{libGL}) it is not part the @TL{} build system. These programs must be built and installed independently, but are contained in the @TL{} DVD together with their support files. @node Extending @subsection Adding New Modules @subsubsection Adding a New Program Module 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 @code{M4} list @code{kpse_texk_pkgs} defined in @file{m4/kpse-pkgs.m4}. 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 @code{M4} list @code{kpse_utils_pkgs} in @file{m4/kpse-pkgs.m4}. Apart from the program sources and build system (@file{configure.ac} and @file{Makefile.am}) the subdirectory @file{texk/@var{prog}} or @file{utils/@var{prog}} must provide a fragment @file{ac/withenable.ac} that contains the @code{M4} macro @code{KPSE_ENABLE_PROG} defined in @file{m4/kpse-setup.m4} with @code{@var{prog}} as mandatory first argument and three optional arguments: a list of required libraries from the @TL{} tree, 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), and a comment added to the help text for the configure option @code{--enable-@var{prog}} or @code{--disable-@var{prog}}. If the module requires specific 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}. @subsubsection Adding a New Generic Library Module A generic library module in a subdirectory @file{libs/@var{lib}} must not depend on @TeX{} specific libraries and is included by adding its name @file{@var{lib}} to the @code{M4} list @code{kpse_libs_pkgs} in @file{m4/kpse-pkgs.m4} (before other libraries from the @TL{} tree it depends on). As for 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 @code{M4} macro @code{KPSE_WITH_LIB} defined in @file{m4/kpse-setup.m4} with @code{@var{lib}} as mandatory first argument and two optional arguments: a list of required libraries from the @TL{} tree, and a list of options (currently only @code{tree} if this library can not be replaced by a system version). If a system version can be used, a second fragment @file{ac/@var{lib}.ac} containing the @code{M4} macro @code{KPSE_TRY_LIB} (or @code{KPSE_TRY_LIBXX}) with @code{@var{lib}} as 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. In addition a file @file{m4/kpse-@var{lib}-flags} (at the top-level) must define the @code{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 (multiline) make rule to rebuild the library when necessary, all that for the library from the @TL{} tree or perhaps for a system version. 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 @code{M4} macro @code{KPSE_@var{LIB}_SYSTEM_FLAGS} to generate the @code{make} variables for a system library. Furthermore the definition of the @code{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])} @subsubsection Adding a New @TeX{} Specific Library Module 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 as is a generic library module with these modifications: @itemize @bullet @item The library name @code{@var{lib}} is added to the @code{M4} list @code{kpse_texlibs_pkgs} also in @file{m4/kpse-pkgs.m4}. @item The fragment @code{ac/withenable.ac} must use @code{KPSE_WITH_TEXLIB}. @end itemize @node Configure Options @section List of all Configure Options Corresponding to the large number of program and library modules there are plenty of configure options, most of which are described here. The command @* @ @ @ @command{configure --help} @* at the top-level gives an exhaustive list of all global options and a few important module specific ones, whereas, e.g., @* @ @ @ @command{texk/lcdf-typetools/configure --help} @* also displays the @code{lcdf-typetools} specific options not shown at the top-level. The help text also mentions several influential environment variables, but for @TL{} it is better to specify them as assigments on the command line. The @file{./Build} script used to make the binaries shipped with @TL{} invokes the top-level @command{configure} with a few additional options. Any defaults discussed below are those for the base @command{configure} script; invoking @command{configure} via @file{./Build} may yield 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 are never modified. @menu * Global Options:: Global Configure Options. * Program Specific Options:: Configure Options for Program Modules. * Library Specific Options:: Configure Options for Library Modules. * Variable Assignments:: Interesting and/or Important Variables. @end menu @node Global Options @subsection Global Configure Options @subsubsection @code{--disable-native-texlive-build} If enabled (the default), build for a @TL{} binary distribution as shipped by the user groups; this requires GNU @command{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 would be used (see below). This may require GNU @command{make}, but will also try without it. A related option @code{--enable-texlive-build} is automatically passed to all subdirectories (and can not be disabled). Subdirectories that could also be built independently from the @TL{} tree (such as @file{utils/xindy} or @file{texk/dvipng}) can use this option, e.g., to choose @TL{} specific installation paths. @subsubsection @code{--prefix}, @code{--exec-prefix}, @code{--bindir}, @dots{} These options specify various installation directories as usual, all of them still prefixed by the value of an assignment for @code{DESTDIR} on the @code{make} command line (@pxref{Staged Installs, , Installation in a temporary location, automake, GNU Automake}). @subsubsection @code{--enable-multiplatform} If enabled, install executables and libraries in platform dependent subdirectories of @file{EPREFIX/bin} and @file{EPREFIX/lib} (unless @code{--bindir=@var{dir}} or @code{--libdir=@var{dir}} is specified), where @code{EPREFIX} is the value given or implied for @code{exec_prefix}. The values for @code{bindir} and @code{libdir} are automatically propagated to all subdirectories. @subsubsection @code{--enable-cxx-runtime-hack} If enabled and when using @code{g++}, try to statically link with @code{libstdc++}, somewhat improving portability. @subsubsection @code{--enable-shared} Build shared versions of the @TeX{} specific libraries such as @file{libkpathsea}; this is not allowed for a native @TL{} build. @subsubsection @code{--disable-largefile} Omit large file support (LFS), needed on most 32-bit Unix systems for files with 2GB or more. The size of @code{DVI} and @code{GF} files must always be @math{<2}GB. With LFS there should be no limit on the size of @code{PDF} files created by @file{pdftex} or @code{PS} files created by @file{dvips}. The size of @code{PDF} images included by @file{pdftex} must, however, be @math{<4}GB when using @file{xpdf} and @math{<2}GB when using older versions of @file{poppler} (even on 64-bit systems with LFS), whereas @file{poppler} Version@tie{}0.23 and later imposes no such limit. @subsubsection @code{--without-x} Disable all programs using the X Window System. @subsubsection @code{--enable-compiler-warnings=[no|min|yes|max|all]} Enable various degrees of compiler warnings for (Objective) C and C++. The default is @code{yes} in maintainer-mode and @code{min} otherwise. This option defines @code{WARNING_[OBJ]C[XX]FLAGS} but these flags are not used in all library and program modules. Using them should help to resolve portability problems. At the moment these warning flags are only defined for the GNU compilers but flags for other compilers could be added when needed. @subsubsection @code{--disable-missing} Immediately terminate the build process if a requested program or feature must be disabled, e.g., due to missing libraries. @subsubsection @code{--enable-silent-rules} Enable the use of less verbose build rules. When using GNU @command{make} or another @command{make} implementation that supports nested variable expansions you can always specify @code{V=1} on the make command line to get more respectively @code{V=0} to get less verbosity. @subsubsection @code{--without-ln-s} Required when using a system without working @code{ln -s} to build binaries for a Unix-like system. But note that @code{make install} will not create anything useful and might even fail. @subsubsection @code{--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. @node Program Specific Options @subsection Configure Options for Program Modules @subsubsection @code{--enable-@var{prog}}, @code{--disable-@var{prog}} Do or do not build and install the program(s) of the module @code{@var{prog}}. @subsubsection @code{--disable-all-pkgs} Do not build any program modules, except those explicitly enabled. Without this option, all modules are built except those that are explicitly disabled or specify @code{disable} in their @file{ac/withenable.ac} fragment. @subsubsection Configure Options for @file{texk/web2c} @noindent @code{--with-banner-add=@var{str}} @* Add @code{@var{str}} to the default version string (@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}}. @noindent @code{--with-editor=@var{cmd}} @* Specify the command @code{@var{cmd}} to invoke from the @code{e} option of @TeX{}-like engines, replacing the default @code{vi +%d '%s'} for Unix or @code{texworks --position=%d "%s"} for Windows. @noindent @code{--enable-auto-core} @* This option causes @TeX{} & METAFONT to produce a core dump when a particular hacky filename is encountered. @noindent @code{--disable-dump-share} @* Make the @code{fmt}/@code{base} dump files architecture dependent (somewhat faster on little-endian architectures). @noindent @code{--disable-ipc} @* Disable @TeX{}'s @code{--ipc} option. @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}). @noindent @code{--enable-tex-synctex}, @code{--disable-etex-synctex}, @dots{} @* Build the various @TeX{}-like engines with or without @code{SyncTeX} support (ignored for a native @TL{} build, defaults are again defined in @file{texk/web2c/ac/web2c.ac}). @noindent @code{--with-fontconfig-includes=@var{dir}}, @code{--with-fontconfig-libdir=@var{dir}} @* Building @code{XeTeX} on non-Mac systems requires installed @code{fontconfig} headers and library. 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). @noindent @code{--enable-libtool-hack} @* If enabled (at present the default for all platforms), prevents @code{libtool} from linking explicitly with dependencies of @file{libfontconfig} such as @file{libexpat}. @noindent @code{--with-mf-x-toolkit} @* Use the X toolkit (@file{libXt}) for METAFONT (default is yes). @noindent @code{--enable-*win} @* Include various types of other window support for METAFONT. @noindent @code{--disable-mf-nowin} @* Do not build a separate non-graphically-capable METAFONT. @noindent @code{--disable-web-progs} @* Do not build the WEB programs @file{bibtex}, @dots{}, @file{weave}, e.g., if you just want to (re)build some engines. @noindent @code{--disable-omfonts} @* Build the WEB versions of the Omega font utilities @file{ofm2opl}, @file{opl2ofm}, @file{ovf2ovp}, and @code{ovp2ovf} instead of the C version @file{omfonts}. The WEB and C versions should be roughly equivalent. @subsubsection Configure Options for @file{texk/bibtex-x} The former modules @code{bibtex8} and @code{bibtexu} have been merged into @code{bibtex-x} (extended BibTeX). @noindent @code{--disable-bibtex8} @* Do not build the @file{bibtex8} program. @noindent @code{--disable-bibtexu} @* Do not build the @file{bibtexu} program (building @file{bibtexu} requires @code{ICU} libraries). @subsubsection Configure Options for @file{texk/dvipdfm-x} The former modules @code{dvipdfmx} and @code{xdvipdfmx} have been merged into @code{dvipdfm-x}. @noindent @code{--disable-dvipdfmx} @* Do not build the @file{dvipdfmx} program. @noindent @code{--disable-xdvipdfmx} @* Do not build the @file{xdvipdfmx} program (building @file{xdvipdfmx} requires the @code{freetype} library). @subsubsection Configure Options for @file{texk/dvisvgm} @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, or otherwise disable support for PostScript specials. @noindent @code{--with-libgs-includes=@var{dir}}, @code{--with-libgs-libdir=@var{dir}} @* Specify non standard locations of the Ghostscript headers and library. @subsubsection Configure Options for @file{texk/xdvik} @noindent @code{--with-gs=@var{path}} @* Hardwire the location of Ghostscript (@file{gs}). @noindent @code{--with-xdvi-x-toolkit=@var{kit}} @* Use toolkit @code{@var{kit}} (@code{motif}/@/@code{xaw}/@/@code{xaw3d}/@/@code{neXtaw}) for @file{xdvi}. The default is @code{motif} if available, else @code{xaw}. @subsubsection Configure Options for @file{utils/xindy} @noindent @code{--enable-xindy-rules} @* Build and install xindy rules (default: yes, except for a native @TL{} build). @noindent @code{--enable-xindy-docs} @* Build and install xindy documentation (default: yes, except for a native @TL{} build). @noindent @code{--with-clisp-runtime=@var{path}} @* Specifies the full path of the @code{CLISP} runtime (@file{lisp.run} or @file{lisp.exe}) to be installed. When specified as @code{default} (the default for a native TeX Live build) the path is determined by the @code{CLISP} executable; the value @code{system} (not allowed for a native @TL{} build, but the default for a non-native one) indicates that @file{xindy} will use the installed version of @file{clisp} (that must be identical to the one used to build @file{xindy}). @noindent @code{--with-recode} @* Use @file{recode} instead of @file{iconv} to build the xindy rules and documentation, required for some systems where @file{iconv} is missing or broken. @node Library Specific Options @subsection Configure Options for Library Modules @subsubsection @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 to also use system versions of all libraries (if any) this library depends on. For many libraries there are in addition @code{--with-@var{lib}-includes=@var{dir}} and @code{--with-@var{lib}-libdir=@var{dir}} to indicate 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 some of these tests fail. @subsubsection Configure Options for @code{kpathsea} @noindent @code{--enable-@var{cmd}-default}, @code{--disable-@var{cmd}-default} @* Determine the compile time default whether or not to run @var{cmd}=@command{mktexmf}, @command{mktexpk}, @command{mktextfm}, @command{mkocp}, @command{mkofm}, @command{mktexfmt}, or @command{mktextex} to generate a missing MF source, PK font, TFM file, OCP file, OFM file, format file, or @TeX{} source respectively. @subsubsection Configure Options for system @file{poppler} Building @code{LuaTeX} and @code{XeTeX} requires @code{poppler} either from the @TL{} tree or system headers and library; @code{pdfTeX} requires either @code{xpdf} from the @TL{} tree or system @code{poppler} headers and library. @noindent @code{--with-system-poppler} @* Use a system version (0.18 or better) of @code{poppler} for @code{LuaTeX} and @code{XeTeX} (and @file{pkg-config} to obtain the required flags). @noindent @code{--with-system-xpdf} @* Use a system version (0.12 or better) of @code{poppler} (and @file{pkg-config}) for @code{pdfTeX} instead of @code{xpdf} from the @TL{} tree. REFER to @code{--disable-largefile} @node Variable Assignments @subsection Interesting and/or Important Variables The values for these variables can be specified as @command{configure} arguments of the form @code{@var{VAR}=@var{value}}. (In principle they could also come from the environment but that might not work for cross compilations.) @subsubsection @code{CC}, @code{CXX}, @code{CPPFLAGS}, @dots{} As usual, these variables specify the name (or full path) of compilers, preprocessor flags, and similar. @subsubsection @code{FT2_CONFIG}, @code{ICU_CONFIG}, @code{PKG_CONFIG} 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 @code{ICU} libraries, or many other libraries. @subsubsection @code{CLISP} Name (or path) of the @file{clisp} executable, used to build @code{xindy}. @subsubsection @code{PERL}, @code{LATEX}, @code{PDFLATEX} Name (or path) for the @file{perl}, @file{latex}, and @file{pdflatex} commands used, e.g., to build the @code{xindy} documentation @subsubsection @code{TL_PLATFORM} The utility program @file{biber} consists of many components bundled by the @code{Par::Packer} mechanism of @file{perl}. Therefore they are not built as part of @TL{} but by the @code{biber} maintainers and third-party builders. In order that @code{make install} creates all executables in @file{bindir}, the @code{biber} module contains pre-made binaries for the platforms for which they are available. @TL{} merely checks if an executable is present for the current platform, and if so, installs it. The complication is hidden in the phrase "current platform". @TL{} has its own ideas about platform names, and the mapping from the canonical system name determined by @file{config.guess} or @file{config.sub} to the @TL{} platform name is not trivial. A value given for @code{TL_PLATFORM} is used as @TL{} platform name. Otherwise, we use copies of the standard @code{perl} modules @code{TeXLive/TLUtils.pm} and @code{TeXLive/TLConfig.pm}, to avoid duplicating the platform-detection logic. @subsubsection @code{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}. @subsubsection @code{MAKE}, @code{SED}, @dots{} Name (or path) of GNU @command{make}, GNU @command{sed}, and similar; used at the top-level and propagated to all subdirectories. @node Cross Compilation @section Cross Compilation In a cross compilation a @code{build} system is used to create binaries to be executed on a @code{host} system with different hardware and/or operating system. 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", this is technically no cross compilation. 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 not be @code{--host=@var{host}} (@pxref{Hosts and Cross-Compilation, , , autoconf, Autoconf})! @menu * Configuring:: Configuring for Cross Compilation. * Problems:: Cross Compilation Problems. @end menu @node Configuring @subsection Configuring for Cross Compilation In a genuine cross compilation binaries for the host system can not 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 @command{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 @command{ar} AR @command{freetype-config} FT2_CONFIG @command{g++} CXX @command{gcc} CC @command{icu-config} ICU_CONFIG @command{objdump} OBJDUMP @command{pkg-config} PKG_CONFIG @command{ranlib} RANLIB @command{strip} STRIP @end example @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 @* @ @ @ @code{--host=i386-pc-mingw32 --build=x86_64-linux-gnu} @* or perhaps @* @ @ @ @code{--host=mingw32 --build=x86_64-linux CC=i386-pc-mingw32-gcc} @* but this might require to add @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 @example BUILDCC=@dots{} BUILDCPPFLAGS=@dots{} BUILDCFLAGS=@dots{} BUILDCXX=@dots{} BUILDCXXFLAGS=@dots{} BUILDLDFLAGS=@dots{} @end example @node Problems @subsection Cross Compilation Problems The fact that binaries for the host system can not 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 can not execute it. Such tests should be avoided if possible and otherwise must supply a pessimistic test result. An other 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/dvipsk/squeeze}, @file{texk/web2c/web2c}, and @file{texk/xdvik/squeeze}. The module @file{libs/freetype} uses the value of @code{CC_BUILD}, @file{@var{build}-gcc}, @file{gcc}, or @file{cc} as compiler for the auxiliary program. The situation for installable programs needed by the build process is somewhat different. A quite expensive possibility, chosen for the @code{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. This 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 to first build a native @code{kpathsea} library. To avoid this complication, cross compilation of the WEB or CWEB programs in this module requires sufficiently recent installed versions of @file{tangle}, @file{ctangle}, @file{otangle}, and @file{tie}. Building @code{xindy} requires to run the host system @file{clisp} binary, thus cross compilation is not possible. @node Coding Rules @section Coding Rules 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 all parts of the @TL{} tree, except some of those maintained independently. @subsection Declarations @subsubsection ANSI C Function Prototypes and Definitions 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 many different systems, some of them not supporting 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++ type comments. If some C99 (or later) constructs have to be used, the module should verify that they are available and otherwise provide an alternative. The module @file{texk/chktex} uses, e.g., the C99 function @code{stpcpy()} that may or may not be available on a particular system, uses @code{AC_CHECK_DECLS([stpcpy])} in @file{configure.ac} to test this, and provides the perhaps slightly less efficient alternative @* @ @ @ @code{#if !(defined HAVE_DECL_STPCPY && HAVE_DECL_STPCPY)} @* @ @ @ @code{static inline char * stpcpy(char *dest, const char *src)} @* @ @ @ @code{@{} @* @ @ @ @code{@ @ @ return strcpy(dest, src) + strlen(src);} @* @ @ @ @code{@}} @* @ @ @ @code{#endif} @* in the file @file{Utility.h}. @subsubsection Static Functions Functions used in only one file should be declared @code{static}; they require no prototype except as forward declaration. @subsubsection Extern Functions Functions not declared @code{static}, usually because they are used in several files, require an (@code{extern}) prototype in exactly one header 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 of functions. There must be no @code{extern} declarations sprinkled throughout the C code (with or without comment where that function is defined). @subsubsection Variables The declaration of global variables must follow analogous rules, they are either declared @code{static} if used in only one files or declared @code{extern} in exactly one header and instantiated in exactly one file. @subsection Const @subsubsection 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. Getting all @code{const} qualifiers right is often quite involved but can be done in most cases. There are, however, a few notable exceptions: the X11 headers are full of declarations that ought to use @code{const} but do not and the same is true to some extent for @file{libfreetype} (but not anymore for @code{zlib}). @subsubsection What Must be Avoided The GCC compiler warnings "assignment discards qualifiers@dots{}" and analogous warnings for "initialization", "passing arg", or "return" must be avoided under all circumstances, except when caused by X11 headers/macros or third party code. @subsubsection What Should be Avoided 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 can not cause the modification of quantities supposed to be constant.