xz/INSTALL

XZ Utils Installation
=====================

    0. Preface
    1. Supported platforms
       1.1. Compilers
       1.2. Platform-specific notes
            1.2.1. Darwin (Mac OS X)
            1.2.2. Tru64
            1.2.3. Windows
            1.2.4. DOS
            1.2.5. OS/2
       1.3. Adding support for new platforms
    2. configure options
    3. xzgrep and other scripts
       3.1. Dependencies
       3.2. PATH
    4. Troubleshooting
       4.1. "No C99 compiler was found."
       4.1. "No POSIX conforming shell (sh) was found."
       4.2. configure works but build fails at crc32_x86.S


0. Preface
----------

    If you aren't familiar with building packages that use GNU Autotools,
    see the file INSTALL.generic for generic instructions before reading
    further.

    If you are going to build a package for distribution, see also the
    file PACKAGERS. It contains information that should help making the
    binary packages as good as possible, but the information isn't very
    interesting to those making local builds for private use or for use
    in special situations like embedded systems.


1. Supported platforms
----------------------

    XZ Utils are developed on GNU/Linux, but they should work on many
    POSIX-like operating systems like *BSDs and Solaris, and even on
    a few non-POSIX operating systems.


1.1. Compilers

    A C99 compiler is required to compile XZ Utils. If you use GCC, you
    need at least version 3.x.x. GCC version 2.xx.x doesn't support some
    C99 features used in XZ Utils source code, thus GCC 2 won't compile
    XZ Utils.

    XZ Utils takes advantage of some GNU C extensions when building
    with GCC. Because these extensions are used only when building
    with GCC, it should be possible to use any C99 compiler.


1.2. Platform-specific notes

1.2.1. Darwin (Mac OS X)

    You may need --disable-assembler if building universal binaries on
    Darwin. This is because different files are built when assembler is
    enabled, and there's no way to make it work with universal build.
    If you want to keep the assembler code, consider building one
    architecture at a time, and then combining the results to create
    universal binaries (see lipo(1)).


1.2.2. Tru64

    If you try to use the native C compiler on Tru64 (passing CC=cc to
    configure), it is possible that the configure script will complain
    that no C99 compiler was found even when the native compiler supports
    C99. You can safely override the test for C99 compiler by passing
    ac_cv_prog_cc_c99= as the argument to the configure script.


1.2.3. Windows

    Building XZ Utils on Windows is supported under MinGW and Cygwin.
    If the Autotools based build gives you trouble with MinGW, you may
    want try the alternative method found from the "windows" directory.

    MSVC doesn't support C99, thus it is not possible to use MSVC to
    compile XZ Utils. However, it is possible to use liblzma.dll from
    MSVC once liblzma.dll has been built with MinGW. The required
    import library for MSVC can be created from liblzma.def using the
    "lib" command shipped in MSVC:

        lib /def:liblzma.def /out:liblzma.lib /machine:ix86

    On x86-64, the /machine argument has to naturally be changed:

        lib /def:liblzma.def /out:liblzma.lib /machine:x64


1.2.4. DOS

    There is an experimental Makefile in the "dos" directory to build
    XZ Utils on DOS using DJGPP. Support for long file names (LFN) is
    needed.

    GNU Autotools based build hasn't been tried on DOS.


1.2.5. OS/2

    You will need to pass --disable-assembler to configure when building
    on OS/2.


1.3. Adding support for new platforms

    If you have written patches to make XZ Utils to work on previously
    unsupported platform, please send the patches to me! I will consider
    including them to the official version. It's nice to minimize the
    need of third-party patching.

    One exception: Don't request or send patches to change the whole
    source package to C89. I find C99 substantially nicer to write and
    maintain. However, the public library headers must be in C89 to
    avoid frustrating those who maintain programs, which are strictly
    in C89 or C++.


2. configure options
--------------------

    In most cases, the defaults are what you want. Most of the options
    below are useful only when building a size-optimized version of
    liblzma or command line tools.

    --enable-encoders=LIST
    --disable-encoders
                Specify a comma-separated LIST of filter encoders to
                build. See "./configure --help" for exact list of
                available filter encoders. The default is to build all
                supported encoders.

                If LIST is empty or --disable-encoders is used, no filter
                encoders will be built and also the code shared between
                encoders will be omitted.

                Disabling encoders will remove some symbols from the
                liblzma ABI, so this option should be used only when it
                is known to not cause problems.

    --enable-decoders=LIST
    --disable-decoders
                This is like --enable-encoders but for decoders. The
                default is to build all supported decoders.

    --enable-match-finders=LIST
                liblzma includes two categories of match finders:
                hash chains and binary trees. Hash chains (hc3 and hc4)
                are quite fast but they don't provide the best compression
                ratio. Binary trees (bt2, bt3 and bt4) give excellent
                compression ratio, but they are slower and need more
                memory than hash chains.

                You need to enable at least one match finder to build the
                LZMA1 or LZMA2 filter encoders. Usually hash chains are
                used only in the fast mode, while binary trees are used to
                when the best compression ratio is wanted.

                The default is to build all the match finders if LZMA1
                or LZMA2 filter encoders are being built.

    --enable-checks=LIST
                liblzma support multiple integrity checks. CRC32 is
                mandatory, and cannot be omitted. See "./configure --help"
                for exact list of available integrity check types.

                liblzma and the command line tools can decompress files
                which use unsupported integrity check type, but naturally
                the file integrity cannot be verified in that case.

                Disabling integrity checks may remove some symbols from
                the liblzma ABI, so this option should be used only when
                it is known to not cause problems.

    --disable-assembler
                liblzma includes some assembler optimizations. Currently
                there is only assembler code for CRC32 and CRC64 for
                32-bit x86.

                All the assembler code in liblzma is position-independent
                code, which is suitable for use in shared libraries and
                position-independent executables. So far only i386
                instructions are used, but the code is optimized for i686
                class CPUs. If you are compiling liblzma exclusively for
                pre-i686 systems, you may want to disable the assembler
                code.

    --enable-unaligned-access
                Allow liblzma to use unaligned memory access for 16-bit
                and 32-bit loads and stores. This should be enabled only
                when the hardware supports this, i.e. when unaligned
                access is fast. Some operating system kernels emulate
                unaligned access, which is extremely slow. This option
                shouldn't be used on systems that rely on such emulation.

                Unaligned access is enabled by default on x86, x86-64,
                and big endian PowerPC.

    --enable-small
                Reduce the size of liblzma by selecting smaller but
                semantically equivalent version of some functions, and
                omit precomputed lookup tables. This option tends to
                make liblzma slightly slower.

                Note that while omitting the precomputed tables makes
                liblzma smaller on disk, the tables are still needed at
                run time, and need to be computed at startup. This also
                means that the RAM holding the tables won't be shared
                between applications linked against shared liblzma.

    --disable-threads
                Disable threading support. This makes some things
                thread-unsafe, meaning that if multithreaded application
                calls liblzma functions from more than one thread,
                something bad may happen.

                Use this option if threading support causes you trouble,
                or if you know that you will use liblzma only from
                single-threaded applications and want to avoid dependency
                on libpthread.

    --enable-dynamic
                Link the command line tools against shared liblzma. The
                default (and recommended way) is to link the command line
                tools against static liblzma.

                This option is mostly useful for packagers, if distro
                policy requires linking against shared libaries. See the
                file PACKAGERS for more information about pros and cons
                of this option.

    --enable-debug
                This enables the assert() macro and possibly some other
                run-time consistency checks. It makes the code slower, so
                you normally don't want to have this enabled.

    --enable-werror
                If building with GCC, make all compiler warnings an error,
                that abort the compilation. This may help catching bugs,
                and should work on most systems. This has no effect on the
                resulting binaries.


3. xzgrep and other scripts
---------------------------

3.1. Dependencies

    POSIX shell (sh) and bunch of other standard POSIX tools are required
    to run the scripts. The configure script tries to find a POSIX
    compliant sh, but if it fails, you can force the shell by passing
    gl_cv_posix_shell=/path/to/posix-sh as an argument to the configure
    script.

    Some of the scripts require also mktemp. The original mktemp can be
    found from <http://www.mktemp.org/>. On GNU, most will use the mktemp
    program from GNU coreutils instead of the original implementation.
    Both mktemp versions are fine for XZ Utils (and practically for
    everything else too).


3.2. PATH

    The scripts assume that the required tools (standard POSIX utilities,
    mktemp, and xz) are in PATH; the scripts don't set the PATH themselves.
    Some people like this while some think this is a bug. Those in the
    latter group can easily patch the scripts before running the configure
    script by taking advantage of a placeholder line in the scripts.

    For example, to make the scripts prefix /usr/bin:/bin to PATH:

        perl -pi -e 's|^#SET_PATH.*$|PATH=/usr/bin:/bin:\$PATH|' \
                src/scripts/xz*.in


4. Troubleshooting
------------------

4.1. "No C99 compiler was found."

    You need a C99 compiler to build XZ Utils. If the configure script
    cannot find a C99 compiler and you think you have such a compiler
    installed, set the compiler command by passing CC=/path/to/c99 as
    an argument to the configure script.

    If you get this error even when you think your compiler supports C99,
    you can override the test by passing ac_cv_prog_cc_c99= as an argument
    to the configure script. The test for C99 compiler is not perfect (and
    it is not as easy to make it perfect as it sounds), so sometimes this
    may be needed. You will get a compile error if your compiler doesn't
    support enough C99.


4.1. "No POSIX conforming shell (sh) was found."

    xzgrep and other scripts need a shell that (roughly) conforms
    to POSIX. The configure script tries to find such a shell. If
    it fails, you can force the shell to be used by passing
    gl_cv_posix_shell=/path/to/posix-sh as an argument to the configure
    script.


4.2. configure works but build fails at crc32_x86.S

    The easy fix is to pass --disable-assembler to the configure script.

    The configure script determines if assembler code can be used by
    looking at the configure triplet; there is currently no check if
    the assembler code can actually actually be built. The x86 assembler
    code should work on x86 GNU/Linux, *BSDs, Solaris, Darwin, MinGW,
    Cygwin, and DJGPP. On other x86 systems, there may be problems and
    the assembler code may need to be disabled with the configure option.

    If you get this error when building for x86-64, you have specified or
    the configure script has misguessed your architecture. Pass the
    correct configure triplet using the --build=CPU-COMPANY-SYSTEM option
    (see INSTALL.generic).