xz: Improve handling of failed realloc in xrealloc.

[xz/debian.git] / INSTALL

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

    0. Preface
    1. Supported platforms
       1.1. Compilers
       1.2. Platform-specific notes
            1.2.1. AIX
            1.2.2. IRIX
            1.2.3. MINIX 3
            1.2.4. OpenVMS
            1.2.5. Solaris, OpenSolaris, and derivatives
            1.2.6. Tru64
            1.2.7. Windows
            1.2.8. DOS
       1.3. Adding support for new platforms
    2. configure options
       2.1. Static vs. dynamic linking of liblzma
       2.2. Optimizing xzdec and lzmadec
    3. xzgrep and other scripts
       3.1. Dependencies
       3.2. PATH
    4. Troubleshooting
       4.1. "No C99 compiler was found."
       4.2. "No POSIX conforming shell (sh) was found."
       4.3. configure works but build fails at crc32_x86.S
       4.4. Lots of warnings about symbol visibility


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. AIX

    If you use IBM XL C compiler, pass CC=xlc_r to configure. If
    you use CC=xlc instead, you must disable threading support
    with --disable-threads (usually not recommended).


1.2.2. IRIX

    MIPSpro 7.4.4m has been reported to produce broken code if using
    the -O2 optimization flag ("make check" fails). Using -O1 should
    work.

    A problem has been reported when using shared liblzma. Passing
    --disable-shared to configure works around this. Alternatively,
    putting "-64" to CFLAGS to build a 64-bit version might help too.


1.2.3. MINIX 3

    The default install of MINIX 3 includes Amsterdam Compiler Kit (ACK),
    which doesn't support C99. Install GCC to compile XZ Utils.

    MINIX 3.1.8 and older have bugs in /usr/include/stdint.h, which has
    to be patched before XZ Utils can be compiled correctly. See
    <http://gforge.cs.vu.nl/gf/project/minix/tracker/?action=TrackerItemEdit&tracker_item_id=537>.

    MINIX 3.2.0 and later use a different libc and aren't affected by
    the above bug.

    XZ Utils doesn't have code to detect the amount of physical RAM and
    number of CPU cores on MINIX 3.

    See section 4.4 in this file about symbol visibility warnings (you
    may want to pass gl_cv_cc_visibility=no to configure).


1.2.4. OpenVMS

    XZ Utils can be built for OpenVMS, but the build system files
    are not included in the XZ Utils source package. The required
    OpenVMS-specific files are maintained by Jouk Jansen and can be
    downloaded here:

        http://nchrem.tnw.tudelft.nl/openvms/software2.html#xzutils


1.2.5. Solaris, OpenSolaris, and derivatives

    The following linker error has been reported on some x86 systems:

        ld: fatal: relocation error: R_386_GOTOFF: ...

    This can be worked around by passing gl_cv_cc_visibility=no
    as an argument to the configure script.


1.2.6. Tru64

    If you try to use the native C compiler on Tru64 (passing CC=cc to
    configure), you may need the workaround mention in section 4.1 in
    this file (pass also ac_cv_prog_cc_c99= to configure).


1.2.7. Windows

    Building XZ Utils on Windows is supported under MinGW + MSYS,
    MinGW-w64 + MSYS, and Cygwin. There is windows/build.bash to
    ease packaging XZ Utils with MinGW(-w64) + MSYS into a
    redistributable .zip or .7z file. See windows/INSTALL-Windows.txt
    for more information.

    It might be possible to build liblzma with a non-GNU toolchain too,
    but that will probably require writing a separate makefile. Building
    the command line tools with non-GNU toolchains will be harder than
    building only liblzma.

    Even if liblzma is built with MinGW, the resulting DLL or static
    library can be used by other compilers and linkers, including MSVC.
    Thus, it shouldn't be a problem to use MinGW to build liblzma even
    if you cannot use MinGW to build the rest of your project. See
    windows/README-Windows.txt for details.


1.2.8. 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. See dos/README for more information.

    GNU Autotools based build hasn't been tried on DOS. If you try, I
    would like to hear if it worked.


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. Many 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-xz
    --disable-xzdec
    --disable-lzmadec
    --disable-lzmainfo
                Don't build and install the command line tool mentioned
                in the option name.

                NOTE: Disabling xz will skip some tests in "make check".

                NOTE: If xzdec is disabled and lzmadec is left enabled,
                a dangling man page symlink lzmadec.1 -> xzdec.1 is
                created.

    --disable-lzma-links
                Don't create symlinks for LZMA Utils compatibility.
                This includes lzma, unlzma, and lzcat. If scripts are
                installed, also lzdiff, lzcmp, lzgrep, lzegrep, lzfgrep,
                lzmore, and lzless will be omitted if this option is used.

    --disable-scripts
                Don't install the scripts xzdiff, xzgrep, xzmore, xzless,
                and their symlinks.

    --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.

                This option doesn't modify CFLAGS to tell the compiler
                to optimize for size. You need to add -Os or equivalent
                flag(s) to CFLAGS manually.

    --enable-assume-ram=SIZE
                On the most common operating systems, XZ Utils is able to
                detect the amount of physical memory on the system. This
                information is used by the options --memlimit-compress,
                --memlimit-decompress, and --memlimit when setting the
                limit to a percentage of total RAM.

                On some systems, there is no code to detect the amount of
                RAM though. Using --enable-assume-ram one can set how much
                memory to assume on these systems. SIZE is given as MiB.
                The default is 128 MiB.

                Feel free to send patches to add support for detecting
                the amount of RAM on the operating system you use. See
                src/common/tuklib_physmem.c for details.

    --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-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.


2.1. Static vs. dynamic linking of liblzma

    On 32-bit x86, linking against static liblzma can give a minor
    speed improvement. Static libraries on x86 are usually compiled as
    position-dependent code (non-PIC) and shared libraries are built as
    position-independent code (PIC). PIC wastes one register, which can
    make the code slightly slower compared to a non-PIC version. (Note
    that this doesn't apply to x86-64.)

    If you want to link xz against static liblzma, the simplest way
    is to pass --disable-shared to configure. If you want also shared
    liblzma, run configure again and run "make install" only for
    src/liblzma.


2.2. Optimizing xzdec and lzmadec

    xzdec and lzmadec are intended to be relatively small instead of
    optimizing for the best speed. Thus, it is a good idea to build
    xzdec and lzmadec separately:

      - To link the tools against static liblzma, pass --disable-shared
        to configure.

      - To select somewhat size-optimized variant of some things in
        liblzma, pass --enable-small to configure.

      - Tell the compiler to optimize for size instead of speed.
        E.g. with GCC, put -Os into CFLAGS.

      - xzdec and lzmadec will never use multithreading capabilities of
        liblzma. You can avoid dependency on libpthread by passing
        --disable-threads to configure.

      - There are and will be no translated messages for xzdec and
        lzmadec, so it is fine to pass also --disable-nls to configure.

      - Only decoder code is needed, so you can speed up the build
        slightly by passing --disable-encoders to configure. This
        shouldn't affect the final size of the executables though,
        because the linker is able to omit the encoder code anyway.

    If you have no use for xzdec or lzmadec, you can disable them with
    --disable-xzdec and --disable-lzmadec.


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.


4.2. "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.


4.3. 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).


4.4. Lots of warnings about symbol visibility

    On some systems where symbol visibility isn't supported, GCC may
    still accept the visibility options and attributes, which will make
    configure think that visibility is supported. This will result in
    many compiler warnings. You can avoid the warnings by forcing the
    visibility support off by passing gl_cv_cc_visibility=no as an
    argument to the configure script. This has no effect on the
    resulting binaries, but fewer warnings looks nicer and may allow
    using --enable-werror.