XZ Utils on Windows
===================

Introduction

    This document explains how to build XZ Utils for Microsoft Windows
    using MinGW (Minimalist GNU for Windows).

    This is currently experimental and has got very little testing.
    No ABI stability is promised for liblzma.dll.


Why MinGW

    XZ Utils code is C99. It should be possible to compile at least
    liblzma using any C99 compiler. Compiling the command line tools may
    need a little extra work to get them built on new systems, because
    they use some features that aren't standardized in POSIX.

    MinGW is free software. MinGW runtime provides some functions that
    made porting the command line tools easier. Most(?) of the MinGW
    runtime, which gets linked into the resulting binaries, is in the
    public domain.

    While most C compilers nowadays support C99 well enough (including
    most compilers for Windows), MSVC doesn't. It seems that Microsoft
    has no plans to ever support C99. Thus, it is not possible to build
    XZ Utils using MSVC without doing a lot of work to convert the code.
    Using prebuilt liblzma from MSVC is possible though, since the
    liblzma API headers are in C89 and contain some non-standard extra
    hacks required by MSVC.


Getting and Installing MinGW

    You can download MinGW for 32-bit Windows from Sourceforge:

        http://sourceforge.net/project/showfiles.php?group_id=2435

    It is enough to pick Automated MinGW Installer and MSYS Base System.
    Using the automated installer, select at least runtime, w32api,
    core compiler, and MinGW make. From MSYS you actually need only
    certain tools, but it is easiest to just install the whole MSYS.

    To build for x86-64 version of Windows, you can download a snapshot
    of MinGW targeting for 64-bit Windows:

        http://sourceforge.net/project/showfiles.php?group_id=202880

    You can use the 32-bit MSYS also for 64-bit build, since we don't
    link against anything in MSYS, just use the tools from it. You may
    use the make tool from 32-bit MinGW (mingw32-make.exe) although
    probably the make.exe from MSYS works too.

    Naturally you can pick the components manually, for example to try
    the latest available GCC. It is also possible to use a cross-compiler
    to build Windows binaries for example on GNU/Linux, or use Wine to
    run the Windows binaries. However, these instructions focus on
    building on Windows.


Building for 32-bit Windows

    Add MinGW and MSYS to PATH (adjust if you installed to non-default
    location):

        set PATH=C:\MinGW\bin;C:\MSYS\1.0\bin;%PATH%

    Then it should be enough to just run mingw32-make in this directory
    (the directory containing this README):

        mingw32-make


Building for 64-bit Windows

    For 64-bit build the PATH has to point to 64-bit MinGW:

        set PATH=C:\MinGW64\bin;C:\MSYS\1.0\bin;%PATH%

    You need to pass W64=1 to mingw32-make (or make if you don't have
    mingw32-make):

        mingw32-make W64=1


Additional Make Flags and Targets

    You may want to try some additional optimizations, which may or
    may not make the code faster (and may or may not hit possible
    compiler bugs more easily):

        mingw32-make CFLAGS="-O3 -fomit-frame-pointer -funroll-loops"

    If you want to enable assertions (the assert() macro), use DEBUG=1.
    You may want to disable optimizations too if you plan to actually
    debug the code. Never use DEBUG=1 for production builds!

        mingw32-make DEBUG=1 CFLAGS="-g -O0"

    To copy the built binaries and required headers into a clean
    directory, use the pkg target:

        mingw32-make pkg

    It first removes a possibly existing pkg directory, and then
    recreates it with the required files.

    TODO: The pkg target doesn't copy any license or other copyright
    related information into the pkg directory.


Creating an Import Library for MSVC

    The included Makefile creates import library liblzma.a which works
    only(?) with MinGW. To use liblzma.dll for MSVC, you need to create
    liblzma.lib using the lib command from 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


To Do

    - Test Win64 support and add instructions about getting x86-64
      version of MinGW.

    - Creating the import library for other compilers/linkers

    - Building with other compilers for Windows

    - liblzma currently uses cdecl. Would stdcall be more compatible?

    - Support building more size-optimized liblzma (the HAVE_SMALL
      define and other things that are needed)

    - Support selecting which parts of liblzma to build to make the
      library even smaller.

    - Use the configure script on Windows just like it is used on all
      the other systems?


Bugs

    Report bugs to <lasse.collin@tukaani.org> (in English or Finnish).

    Take into account that I don't have MSVC and I cannot very easily
    test anything on Windows. As of writing, I have tried MinGW and the
    resulting binaries only under 32-bit Wine.