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authorLasse Collin <lasse.collin@tukaani.org>2024-02-18 17:17:43 +0200
committerLasse Collin <lasse.collin@tukaani.org>2024-02-21 16:57:20 +0200
commit8d38941baed05de4ff7cc775de14833108f62184 (patch)
treedae5fcc9ea37ec7a24fd0e549ad1de328ae3b7b9
parentWindows: Update windows/README-Windows.txt. (diff)
downloadxz-8d38941baed05de4ff7cc775de14833108f62184.tar.xz
Windows: Major update to Windows build instructions.
-rw-r--r--INSTALL68
-rw-r--r--windows/INSTALL-MSVC.txt23
-rw-r--r--windows/INSTALL-MinGW-w64_with_Autotools.txt49
-rw-r--r--windows/INSTALL-MinGW-w64_with_CMake.txt203
-rw-r--r--windows/INSTALL-MinGW.txt138
-rw-r--r--windows/README-Windows.txt2
-rw-r--r--windows/build-with-cmake.bat35
-rw-r--r--windows/liblzma-crt-mixing.txt70
8 files changed, 404 insertions, 184 deletions
diff --git a/INSTALL b/INSTALL
index 670e3989..004fc87d 100644
--- a/INSTALL
+++ b/INSTALL
@@ -143,43 +143,37 @@ XZ Utils Installation
1.2.7. Windows
- If it is enough to build liblzma (no command line tools):
-
- - There is CMake support. It should be good enough to build
- static liblzma or liblzma.dll with Visual Studio. The CMake
- support may work with MinGW or MinGW-w64. Read the comment
- in the beginning of CMakeLists.txt before running CMake!
-
- - There are Visual Studio project files under the "windows"
- directory. See windows/INSTALL-MSVC.txt. In the future the
- project files will be removed when CMake support is good
- enough. Thus, please test the CMake version and help fix
- possible issues.
-
- To build also the command line tools:
-
- - MinGW-w64 + MSYS (32-bit and 64-bit x86): This is used
- for building the official binary packages for Windows.
- There is windows/build.bash to ease packaging XZ Utils with
- MinGW(-w64) + MSYS into a redistributable .zip or .7z file.
- See windows/INSTALL-MinGW.txt for more information.
-
- - MinGW + MSYS (32-bit x86): I haven't recently tested this.
-
- - Cygwin 1.7.35 and later: NOTE that using XZ Utils >= 5.2.0
- under Cygwin older than 1.7.35 can lead to DATA LOSS! If
- you must use an old Cygwin version, stick to XZ Utils 5.0.x
- which is safe under older Cygwin versions. You can check
- the Cygwin version with the command "cygcheck -V".
-
- It may be possible to build liblzma with other toolchains 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(-w64), the resulting DLL can
- be used by other compilers and linkers, including MSVC. See
- windows/README-Windows.txt for details.
+ The "windows" directory contains instructions for a few types
+ of builds:
+
+ - INSTALL-MinGW-w64_with_CMake.txt
+ Simple instructions how to build XZ Utils natively on
+ Windows using only CMake and a prebuilt toolchain
+ (GCC + MinGW-w64 or Clang/LLVM + MinGW-w64).
+
+ - INSTALL-MinGW-w64_with_Autotools.txt
+ Native build under MSYS2 or cross-compilation from
+ GNU/Linux using a bash script that creates a .zip
+ and .7z archives of the binaries and documentation.
+ The related file README-Windows.txt is for the
+ resulting binary package.
+
+ - INSTALL-MSVC.txt
+ Building with MSVC / Visual Studio and CMake.
+
+ - liblzma-crt-mixing.txt
+ Documentation what to take into account as a programmer
+ if liblzma.dll and the application don't use the same
+ CRT (MSVCRT or UCRT).
+
+ Other choices:
+
+ - Cygwin: https://cygwin.com/
+ Building on Cygwin can be done like on many POSIX operating
+ systems. XZ Utils >= 5.2.0 isn't compatible with Cygwin older
+ than 1.7.35 (data loss!). 1.7.35 was released on 2015-03-04.
+
+ - MSYS2: https://www.msys2.org/
1.2.8. DOS
diff --git a/windows/INSTALL-MSVC.txt b/windows/INSTALL-MSVC.txt
index d9574388..ba483fb6 100644
--- a/windows/INSTALL-MSVC.txt
+++ b/windows/INSTALL-MSVC.txt
@@ -5,11 +5,15 @@ Building XZ Utils with Microsoft Visual Studio
Introduction
------------
- liblzma got MSVC support in XZ Utils 5.2.0, and the xz and xzdec
- command line tools in XZ Utils 5.6.0.
+ liblzma got MSVC support in XZ Utils 5.2.0, and the xz, xzdec,
+ lzmadec, and lzmainfo command line tools in XZ Utils 5.6.0.
- Note: xz and xzdec depend on the the included GNU getopt
- which is licensed under the GNU LGPLv2.1.
+ NOTE: The *.exe files are linked against GNU getopt_long from
+ the "lib" directory. That code is under the GNU LGPLv2.1
+ and thus the matching source code must be provided when
+ distributing the *.exe files. The simplest way to comply with
+ the license requirements is to distribute the matching XZ Utils
+ source package alongside the *.exe files.
MSVC 2013 update 2 and later have enough C99 support to build
liblzma from XZ Utils 5.2.0 and later without modifications.
@@ -21,12 +25,13 @@ Introduction
Building
--------
- It is recommended to use CMake to generate build files for MSVC.
- Visual Studio project files are no longer provided (XZ Utils 5.4.x
- were the last versions to include the project files).
+ Use CMake to generate build files for MSVC. Visual Studio project
+ files are no longer provided (XZ Utils 5.4.x were the last versions
+ to include the project files).
- CMake-based build includes tests for liblzma but not for the
- command line tools.
+ NOTE: GCC and Clang compatible inline assembly isn't supported by
+ the MSVC compiler. Using clang-cl under MSVC should make inline
+ assembly work (untested).
Notes
diff --git a/windows/INSTALL-MinGW-w64_with_Autotools.txt b/windows/INSTALL-MinGW-w64_with_Autotools.txt
new file mode 100644
index 00000000..89c74409
--- /dev/null
+++ b/windows/INSTALL-MinGW-w64_with_Autotools.txt
@@ -0,0 +1,49 @@
+
+Creating XZ Utils Windows package with build.bash
+=================================================
+
+Introduction
+------------
+
+ The script build.bash can be used for building XZ Utils with
+ GCC + MinGW-w64 under MSYS2, under the ancient MSYS, or
+ cross-compiling from GNU/Linux. The script will create a package
+ with binaries and documentation in a hopefully-convenient bundle.
+
+ NOTE: build.bash requires files that are only included
+ in release tarballs. If building from xz.git, a distribution
+ tarball should be created first.
+
+ For native builds on Windows, the CMake-based build described
+ in the file INSTALL-MinGW-w64_with_CMake.txt is simpler to do as
+ it has no need for MSYS2 and it works from xz.git without extra
+ steps. For cross-compilation and package creation the script can
+ be convenient though.
+
+ These instructions are for making a package with build.bash and thus
+ don't apply to normal Autotool-based builds under Cygwin or MSYS2.
+
+
+Usage
+-----
+
+ First copy the file COPYING.MinGW-w64-runtime.txt from MinGW-w64
+ to this directory. It contains copyright and license notices that
+ apply to the MinGW-w64 runtime that gets statically linked into
+ the XZ Utils binaries being built. build.bash will include the file
+ in the final package.
+
+ Put i686 and/or x86_64 GCC-based toolchain in PATH depending on
+ which builds are wanted.
+
+ Optional: Put the 7z tool from 7-Zip or p7zip in PATH. Without
+ this, .zip and .7z files won't be created from the finished "pkg"
+ directory contents.
+
+ Run build.bash:
+
+ bash windows/build.bash
+
+ Note that it does an in-tree build so the build files will be mixed
+ with the source files in the same directory tree.
+
diff --git a/windows/INSTALL-MinGW-w64_with_CMake.txt b/windows/INSTALL-MinGW-w64_with_CMake.txt
new file mode 100644
index 00000000..5d2be5ba
--- /dev/null
+++ b/windows/INSTALL-MinGW-w64_with_CMake.txt
@@ -0,0 +1,203 @@
+
+Building XZ Utils on Windows using MinGW-w64 and CMake
+======================================================
+
+ 1. Introduction
+ 1.1. Licensing considerations
+ 2. MSVCRT or UCRT
+ 3. CMake
+ 4. MinGW-w64 toolchains
+ 4.1. MinGW-w64 with GCC
+ 4.2. MinGW-w64 with Clang/LLVM
+ 5. Building XZ Utils
+ 5.1. Advanced build options
+ 6. Creating an import library for MSVC / Visual Studio
+
+
+1. Introduction
+---------------
+
+ This document explains how to build XZ Utils using MinGW-w64,
+ GCC or Clang/LLVM, CMake, and GNU make (mingw32-make) natively
+ on Windows. The resulting XZ Utils library and executable files
+ will only depend on DLLs that are included in Windows.
+
+ The build tools can be extracted into separate directories and used
+ directly from there and deleted when no longer needed. There are no
+ installers to run for these and no configuration needed.
+
+ These instructions don't apply to Cygwin. XZ Utils can be built
+ under Cygwin in the same way as many other packages.
+
+
+1.1. Licensing considerations
+
+ Parts of MinGW-w64 runtime are statically linked into the binaries
+ being built. The file COPYING.MinGW-w64-runtime.txt in MinGW-w64
+ contains the license notices that apply to some parts of the
+ runtime. The notices must be distributed alongside the binaries
+ that have been built with MinGW-w64.
+
+ MinGW-w64 includes getopt_long(). The GNU getopt_long() (LGPLv2.1)
+ included in XZ Utils isn't used when building with MinGW-w64.
+
+ The code from XZ Utils that ends up liblzma.dll and the *.exe files
+ is under the BSD Zero Clause License (0BSD) which doesn't require
+ any copyright or license notices to be included when distributing
+ the binaries. See the file COPYING in the parent directory.
+
+
+2. MSVCRT or UCRT
+-----------------
+
+ Both GCC and Clang/LLVM based MinGW-w64 toolchains come in MSVCRT
+ and Universal C runtime (UCRT) variants. MSVCRT is the old one.
+ 32-bit builds of XZ Utils with MSVCRT should run on Windows 2000
+ and later (even Windows 95 should still be possible with trivial
+ edits to the source code).
+
+ UCRT is included in Windows 10, and it's possible to install UCRT
+ on Windows XP and later. UCRT might be the preferred choice if
+ out-of-the-box compatibility with Windows versions older than 10
+ is not required. Visual Studio 2015 and later produce binaries
+ that use UCRT.
+
+ If you want to build liblzma.dll for use with your application,
+ it's recommended to use the same CRT for all components. If this
+ isn't possible, see the file liblzma-crt-mixing.txt.
+
+ If you only need the command line tools, the choice of CRT isn't
+ important, at least for now.
+
+
+3. CMake
+--------
+
+ CMake is used for selecting build options and generating makefiles.
+ It can also be used to extract archives, including .tar.xz and .7z.
+
+ Download a CMake binary package (.zip) from its homepage:
+
+ https://cmake.org/download/
+
+ Extract it to, for example, C:\devel\cmake so that the executables
+ end up in C:\devel\cmake\bin. Avoid spaces and other special
+ characters in the path.
+
+
+4. MinGW-w64 toolchains
+-----------------------
+
+ There are a few choices of prebuilt toolchains listed on
+ the MinGW-w64 homepage:
+
+ https://www.mingw-w64.org/downloads/
+
+ These instructions list one GCC-based version and one
+ Clang/LLVM-based version. Both include mingw32-make too.
+
+
+4.1. MinGW-w64 with GCC
+
+ For GCC, download appropriate packages from Mingw-builds depending
+ on if you want to build 32-bit or 64-bit x86 version of XZ Utils
+ and if the XZ Utils binaries should link against MSVCRT or UCRT:
+
+ https://github.com/niXman/mingw-builds-binaries/releases
+
+ i686-*-release-win32-*-msvcrt-*.7z 32-bit, uses MSVCRT (old)
+ i686-*-release-win32-*-ucrt-*.7z 32-bit, uses UCRT (new)
+ x86_64-*-release-win32-*-msvcrt-*.7z 64-bit, uses MSVCRT (old)
+ x86_64-*-release-win32-*-ucrt-*.7z 64-bit, uses UCRT (new)
+
+ Extract it, for example, to C:\devel so that the executables are
+ in C:\devel\mingw32\bin or C:\devel\mingw64\bin. To extract,
+ you can install 7-Zip from <https://7-zip.org/> or use CMake
+ on the command line:
+
+ set PATH=C:\devel\cmake\bin;%PATH%
+ c:
+ cd \devel
+ cmake -E tar xf x86_64-13.1.0-release-win32-seh-ucrt-rt_v11-rev1.7z
+
+ Then skip to the section "Building XZ Utils".
+
+
+4.2. MinGW-w64 with Clang/LLVM
+
+ For Clang/LLVM, download an appropriate package from LLVM-MinGW:
+
+ https://github.com/mstorsjo/llvm-mingw/releases
+
+ llvm-mingw-*-msvcrt-i686.zip 32-bit, uses MSVCRT (old)
+ llvm-mingw-*-ucrt-i686.zip 32-bit, uses UCRT (new)
+ llvm-mingw-*-msvcrt-x86_64.zip 64-bit, uses MSVCRT (old)
+ llvm-mingw-*-ucrt-x86_64.zip 64-bit, uses UCRT (new)
+
+ Extract it, for example, to C:\devel so that the executables end up
+ in a directory like C:\devel\llvm-mingw-20230919-ucrt-x86_64\bin.
+
+
+5. Building XZ Utils
+--------------------
+
+ For a simple builds, you can use the included build-with-cmake.bat
+ which takes these arguments:
+
+ %1 = Path to CMake's bin directory. Example:
+ c:\devel\cmake\bin
+
+ %2 = Path to MinGW-w64's bin directory. Example:
+ c:\devel\mingw64\bin
+
+ %3 = ON or OFF: Set to ON to build liblzma.dll or OFF for
+ static liblzma.a. With OFF, the *.exe files won't
+ depend on liblzma.dll.
+
+ Example:
+
+ build-with-cmake C:\devel\cmake\bin C:\devel\mingw64\bin ON
+
+ If successful, the "build" directory should then contain:
+
+ liblzma.dll liblzma compression library
+ liblzma.def DEF file for creating an import library
+ xz.exe xz command line tool
+ xzdec.exe Decompression-only tool (smaller than xz.exe)
+ lzmadec.exe Decompression-only tool for legacy .lzma files
+ lzmainfo.exe Shows header info of legacy .lzma files
+
+ Ignore the other files. :-)
+
+
+5.1. Advanced build options
+
+ For 32-bit x86 builds, adding -msse2 to CFLAGS improves
+ compression speed a little (but not decompression speed).
+ There is no runtime detection for SSE2 support. It is
+ recommended to use 64-bit version when possible.
+
+ It's possible to omit features from the build to reduce code size.
+ There are several CMake configuration options available. One may
+ change from CMAKE_BUILD_TYPE=Release to =MinSizeRel as well but
+ it makes the code slower.
+
+ If building for multiple targets, keep only one toolchain in PATH
+ at a time.
+
+
+6. Creating an import library for MSVC / Visual Studio
+------------------------------------------------------
+
+ To link against liblzma.dll, you need to create an import library
+ first. You need the "lib" command from MSVC and liblzma.def. Here
+ is the command that works on 32-bit x86:
+
+ lib /def:liblzma.def /out:liblzma.lib /machine:ix86
+
+ On x86-64, the /machine argument has to be changed:
+
+ lib /def:liblzma.def /out:liblzma.lib /machine:x64
+
+ IMPORTANT: See also the file liblzma-crt-mixing.txt.
+
diff --git a/windows/INSTALL-MinGW.txt b/windows/INSTALL-MinGW.txt
deleted file mode 100644
index 72e2718f..00000000
--- a/windows/INSTALL-MinGW.txt
+++ /dev/null
@@ -1,138 +0,0 @@
-
-Building XZ Utils on Windows
-============================
-
-Introduction
-------------
-
- This document explains shortly where to get and how to install the
- build tools that are needed to build XZ Utils on Windows. The final
- binary package will be standalone in sense that it will depend only
- on DLLs that are included in all Windows installations.
-
- These instructions don't apply to Cygwin. XZ Utils can be built under
- Cygwin in the same way as many other packages.
-
- These instructions don't apply to MinGW and MSYS developers either,
- who may want to package XZ Utils for MinGW or MSYS distributions.
- You know who you are, and will probably use quite different configure
- options etc. than what is described here.
-
-
-Installing the toolchain(s)
----------------------------
-
- Some of the following is needed:
- - MSYS is always needed to use the GNU Autotools based build system.
- - MinGW builds 32-bit x86 binaries.
- - 32-bit MinGW-w64 (I call it MingW-w32 here) builds 32-bit x86
- executables too.
- - MinGW-w64 builds 64-bit x86-64 binaries.
-
- So you need to pick between MinGW and MinGW-w32 when building
- 32-bit version. You don't need both.
-
- You might find 7-Zip <https://7-zip.org/> handy when extracting
- some files. The ready-made build script build.bash will also use
- 7-Zip to create the distributable .zip and .7z files.
-
- I used the following directory structure but you can use whatever
- you want. Just note that I will use these in my examples. Each of
- these should have a subdirectory "bin":
-
- C:\devel\tools\msys
- C:\devel\tools\mingw
- C:\devel\tools\mingw-w32
- C:\devel\tools\mingw-w64
-
-
-Installing MSYS
-
- You can download MSYS from MinGW's Sourceforge page:
-
- https://sourceforge.net/projects/mingw/files/MSYS/Base/msys-core/
-
- I recommend using MSYS 1.0.11 (MSYS-1.0.11.exe or
- msysCORE-1.0.11-bin.tar.gz) because that package includes all the
- required tools. At least some of the later versions include only
- a subset and thus you would need to download the rest separately.
- The old version will work fine for building XZ Utils.
-
- You can use either the .exe or .tar.gz package. I prefer .tar.gz,
- because it can be extracted into any directory and later removed
- without worrying about uninstallers.
-
-
-Installing MinGW
-
- NOTE: This section may be outdated. I haven't tried MinGW recently.
-
- You can download the required packages from MinGW's Sourceforge page:
-
- https://sourceforge.net/projects/mingw/files/
-
- These version numbers were the latest when I wrote this document, but
- you probably should pick the latest versions:
-
- MinGW Runtime -> mingwrt-3.17-mingw32-dev.tar.gz
- MinGW API for MS-Windows -> w32api-3.14-mingw32-dev.tar.gz
- GNU Binutils -> binutils-2.20-1-bin.tar.gz
- GCC Version 4 -> gcc-full-4.4.0-mingw32-bin-2.tar.lzma
-
- The full GCC package is quite big, but if you want a smaller
- download, you will need to download more than one file, so I'm
- using the full package in this document for simplicity.
-
- Extract the packages in the above order, possibly overwriting files
- from packages that were extracted earlier.
-
-
-Installing MinGW-w32 or MinGW-w64
-
- I used the packages from Mingw-builds project. With that it is
- enough to pick one .7z file for 32-bit and another for 64-bit
- toolchain. For XZ Utils 5.2.0 I used the packages from these
- directories:
-
- https://sourceforge.net/projects/mingw-w64/files/Toolchains%20targetting%20Win32/Personal%20Builds/mingw-builds/4.9.2/threads-win32/sjlj/
-
- https://sourceforge.net/projects/mingw-w64/files/Toolchains%20targetting%20Win64/Personal%20Builds/mingw-builds/4.9.2/threads-win32/sjlj/
-
- If you install both MinGW-w32 and MinGW-w64, remember to extract
- them into different directories. build.bash looks at
- C:\devel\tools\mingw-w32 and C:\devel\tools\mingw-w64 by default.
-
-
-Building XZ Utils
------------------
-
- Start MSYS by going to the directory C:\devel\tools\msys and running
- msys.bat there (double-click or use command prompt). It will start
- at "home" directory, which is C:\devel\tools\msys\home\YourUserName.
-
- If you have xz-5.x.x.tar.gz in C:\devel, you should be able to build
- it now with the following commands:
-
- cd /c/devel
- tar xzf xz-5.x.x.tar.gz
- cd xz-5.x.x
- bash windows/build.bash
-
- If you used some other directory than C:\devel\tools for the build
- tools, edit the variables near the beginning of build.bash first.
-
- If you want to build manually, read the buildit() function in
- build.bash. Look especially at the latter configure invocation.
-
- Be patient. Running configure and other scripts used by the build
- system is (very) slow under Windows.
-
-
-Using a snapshot from the Git repository
-
- To use a snapshot, the build system files need to be generated with
- autogen.sh or "autoreconf -fi" before trying to build using the
- above build instructions. You can install the relevant extra packages
- from MinGW or use Cygwin or use e.g. a GNU/Linux system to create a
- source package with the required build system files.
-
diff --git a/windows/README-Windows.txt b/windows/README-Windows.txt
index 65dc9db1..c7820f8c 100644
--- a/windows/README-Windows.txt
+++ b/windows/README-Windows.txt
@@ -92,6 +92,8 @@ Creating an import library for MSVC / Visual Studio
lib /def:liblzma.def /out:liblzma.lib /machine:x64
+ IMPORTANT: See also the file liblzma-crt-mixing.txt.
+
Reporting bugs
--------------
diff --git a/windows/build-with-cmake.bat b/windows/build-with-cmake.bat
new file mode 100644
index 00000000..24978ba8
--- /dev/null
+++ b/windows/build-with-cmake.bat
@@ -0,0 +1,35 @@
+@rem # SPDX-License-Identifier: 0BSD
+@rem # Author: Lasse Collin
+@rem #
+@rem ########################################################################
+@rem #
+@rem # This builds XZ Utils with CMake + MinGW-w64 (GCC or Clang/LLVM).
+@rem # See INSTALL-MinGW-w64_with_CMake.txt for detailed instructions.
+@rem #
+@rem # Summary of command line arguments:
+@rem #
+@rem # %1 = Path to CMake's bin directory. Example:
+@rem # C:\devel\cmake\bin
+@rem #
+@rem # %2 = Path to MinGW-w64's bin directory. Example:
+@rem # C:\devel\mingw64\bin
+@rem #
+@rem # %3 = ON or OFF: Set to ON to build liblzma.dll or OFF for
+@rem # static liblzma.a. With OFF, the *.exe files won't
+@rem # depend on liblzma.dll.
+@rem #
+@rem ########################################################################
+
+setlocal
+set PATH=%1;%2;%PATH%
+
+md build || exit /b
+cd build || exit /b
+
+cmake -G "MinGW Makefiles" -DCMAKE_BUILD_TYPE=Release -DENABLE_NLS=OFF -DBUILD_SHARED_LIBS=%3 ..\.. || exit /b
+mingw32-make || exit /b
+mingw32-make test || exit /b
+
+@rem liblzma.dll might not exist so ignore errors.
+strip xz.exe xzdec.exe lzmadec.exe lzmainfo.exe liblzma.dll
+exit /b 0
diff --git a/windows/liblzma-crt-mixing.txt b/windows/liblzma-crt-mixing.txt
new file mode 100644
index 00000000..4ef2f8ab
--- /dev/null
+++ b/windows/liblzma-crt-mixing.txt
@@ -0,0 +1,70 @@
+
+liblzma.dll and mixing C runtimes (CRTs)
+----------------------------------------
+
+ If possible, liblzma.dll should be linked against the same CRT
+ (MSVCRT or UCRT) as the application calling the liblzma functions.
+ When this isn't possible, liblzma.dll will still work but there
+ are a few API functions that need extra care.
+
+ Each CRT has its own memory allocator, stdio FILE implementation,
+ mapping of file descriptors from _open() to Windows' HANDLEs, and
+ so on. Mixing CRTs is a problem if, for example, one library calls
+ fopen() and then passes the resulting FILE* to a second library and
+ these two libraries use different CRTs. liblzma doesn't expose FILE
+ pointers or file descriptors in the API but the problem can occur
+ with memory allocation with a few specific functions.
+
+ The most commonly-used API functions in liblzma are such that both
+ memory allocation and deallocation is done internally by liblzma,
+ thus most applications won't have any problems with mixing CRTs
+ with liblzma.dll. The following API functions are the exception:
+
+ lzma/block.h:
+ lzma_block_header_decode
+
+ lzma/filter.h:
+ lzma_filters_copy
+ lzma_filters_free
+ lzma_properties_decode
+ lzma_filter_flags_decode
+ lzma_str_to_filters
+ lzma_str_from_filters
+ lzma_str_list_filters
+
+ Excluding lzma_filters_free(), the above functions allocate memory
+ and leave it to the caller to free it. lzma_filters_free() frees
+ memory given to it, and that memory may have been allocated outside
+ of liblzma.
+
+ For example, if application calls lzma_str_list_filters(&ptr, ...)
+ and then uses free(ptr), something bad (memory corruption, crash)
+ will happen if the application and liblzma.dll aren't using the
+ same CRT. This can be worked around with a few lines of extra code.
+
+ All these functions (and many others too) take a pointer to
+ lzma_allocator structure as an argument. Typically it is set to
+ NULL to let liblzma use malloc() and free() (and also calloc()
+ as it is faster than malloc() + memset()). A custom lzma_allocator
+ can be used to wrap malloc() and free() from application's CRT:
+
+ static void * LZMA_API_CALL
+ my_alloc(void *opaque, size_t nmemb, size_t size)
+ {
+ // liblzma guarantees that this won't overflow.
+ return malloc(nmemb * size);
+ }
+
+ static void LZMA_API_CALL
+ my_free(void *opaque, void *ptr)
+ {
+ free(ptr);
+ }
+
+ static const lzma_allocator allocator
+ = { &my_alloc, &my_free, NULL };
+
+ By passing &allocator to the problematic functions, CRT mixing
+ should not cause any problems. There is no need to use &allocator
+ with functions other than those listed above.
+