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Issue 2869016: Add an unpatched version of xz, XZ Utils, to /trunk/deps/third_party (Closed) Base URL: svn://svn.chromium.org/chrome/trunk/deps/third_party/
Patch Set: Created 10 years, 6 months ago
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1
2 Information to packagers of XZ Utils
3 ====================================
4
5 0. Preface
6 1. Package naming
7 2. Package description
8 3. License
9 4. configure options
10 4.1. Static vs. dynamic linking of liblzma
11 4.2. Optimizing xzdec and lzmadec
12 5. Additional documentation
13 6. Extra files
14 7. Installing XZ Utils and LZMA Utils in parallel
15 8. Example
16
17
18 0. Preface
19 ----------
20
21 This document is meant for people who create and maintain XZ Utils
22 packages for operating system distributions. The focus is on GNU/Linux
23 systems, but most things apply to other systems too.
24
25 While the standard "configure && make DESTDIR=$PKG install" should
26 give a pretty good package, there are some details which packagers
27 may want to tweak.
28
29 Packagers should also read the INSTALL file.
30
31
32 1. Package naming
33 -----------------
34
35 The preferred name for the XZ Utils package is "xz", because that's
36 the name of the upstream tarball. Naturally you may have good reasons
37 to use some other name; I won't get angry about it. ;-) It's just nice
38 to be able to point people to the correct package name without asking
39 what distro they have.
40
41 If your distro policy is to split things into small pieces, here is
42 one suggestion:
43
44 xz xz, xzdec, scripts (xzdiff, xzgrep, etc.), docs
45 xz-lzma lzma, unlzma, lzcat, lzgrep etc. symlinks and
46 lzmadec binary for compatibility with LZMA Utils
47 liblzma liblzma.so.*
48 liblzma-devel liblzma.so, liblzma.a, API headers
49
50
51 2. Package description
52 ----------------------
53
54 Here is a suggestion which you may use as the package description.
55 If you can use only one-line description, pick only the first line.
56 Naturally, feel free to use some other description if you find it
57 better, and maybe send it to me too.
58
59 Library and command line tools for XZ and LZMA compressed files
60
61 XZ Utils provide a general purpose data compression library
62 and command line tools. The native file format is the .xz
63 format, but also the legacy .lzma format is supported. The .xz
64 format supports multiple compression algorithms, of which LZMA2
65 is currently the primary algorithm. With typical files, XZ Utils
66 create about 30 % smaller files than gzip.
67
68 If you are splitting XZ Utils into multiple packages, here are some
69 suggestions for package descriptions:
70
71 xz:
72
73 Command line tools for XZ and LZMA compressed files
74
75 This package includes the xz compression tool and other command
76 line tools from XZ Utils. xz has command line syntax similar to
77 that of gzip. The native file format is the .xz format, but also
78 the legacy .lzma format is supported. The .xz format supports
79 multiple compression algorithms, of which LZMA2 is currently the
80 primary algorithm. With typical files, XZ Utils create about 30 %
81 smaller files than gzip.
82
83 Note that this package doesn't include the files needed for
84 LZMA Utils 4.32.x compatibility. Install also the xz-lzma
85 package to make XZ Utils emulate LZMA Utils 4.32.x.
86
87 xz-lzma:
88
89 LZMA Utils emulation with XZ Utils
90
91 This package includes executables and symlinks to make
92 XZ Utils emulate lzma, unlzma, lzcat, and other command
93 line tools found from the legacy LZMA Utils 4.32.x package.
94
95 liblzma:
96
97 Library for XZ and LZMA compressed files
98
99 liblzma is a general purpose data compression library with
100 an API similar to that of zlib. liblzma supports multiple
101 algorithms, of which LZMA2 is currently the primary algorithm.
102 The native file format is .xz, but also the legacy .lzma
103 format and raw streams (no headers at all) are supported.
104
105 This package includes the shared library.
106
107 liblzma-devel:
108
109 Library for XZ and LZMA compressed files
110
111 This package includes the API headers, static library, and
112 other development files related to liblzma.
113
114
115 3. License
116 ----------
117
118 If the package manager supports a license field, you probably should
119 put GPLv2+ there (GNU GPL v2 or later). The interesting parts of
120 XZ Utils are in the public domain, but some less important files
121 ending up into the binary package are under GPLv2+. So it is simplest
122 to just say GPLv2+ if you cannot specify "public domain and GPLv2+".
123
124 If you split XZ Utils into multiple packages as described earlier
125 in this file, liblzma and liblzma-dev packages will contain only
126 public domain code (from XZ Utils at least; compiler or linker may
127 add some third-party code, which may be copyrighted).
128
129
130 4. configure options
131 --------------------
132
133 Unless you are building a package for a distribution that is meant
134 only for embedded systems, don't use the following configure options:
135
136 --enable-debug
137 --enable-encoders (*)
138 --enable-decoders
139 --enable-match-finders
140 --enable-checks
141 --enable-small (*)
142 --disable-threads (*)
143
144 (*) These are OK when building xzdec and lzmadec as explained later.
145
146 You may use --enable-werror but be careful with it since it may break
147 the build due to some useless warning when the build environment
148 changes (like CPU architecture or compiler version).
149
150
151 4.1. Static vs. dynamic linking of liblzma
152
153 The default is to link the most important command line tools against
154 static liblzma, and the less important tools against shared liblzma.
155 This can be changed by passing --enable-dynamic to configure, or by
156 not building static libraries at all by passing --disable-static
157 to configure. It is mildly recommended that you use the default, but
158 the configure options make it easy to do otherwise if the distro policy
159 so requires.
160
161 On 32-bit x86, linking against static liblzma can give a minor
162 speed improvement. Static libraries on x86 are usually compiled as
163 position-dependent code (non-PIC) and shared libraries are built as
164 position-independent code (PIC). PIC wastes one register, which can
165 make the code slightly slower compared to a non-PIC version. (Note
166 that this doesn't apply to x86-64.)
167
168 Linking against static liblzma avoids a dependency on liblzma shared
169 library, and makes it slightly easier to copy the command line tools
170 between systems (e.g. quick 'n' dirty emergency recovery of some
171 files). It also allows putting the command line tools to /bin while
172 leaving liblzma to /usr/lib (assuming that your distribution uses
173 such a file system hierarchy), if no other file in /bin would require
174 liblzma.
175
176 If you don't want to distribute static libraries but you still
177 want to link the command line tools against static liblzma, it is
178 probably easiest to build both static and shared liblzma, but after
179 "make DESTDIR=$PKG install" remove liblzma.a and modify liblzma.la
180 to not contain a reference to liblzma.a.
181
182
183 4.2. Optimizing xzdec and lzmadec
184
185 xzdec and lzmadec are intended to be relatively small instead of
186 optimizing for the best speed. Thus, it is a good idea to build
187 xzdec and lzmadec separately:
188
189 - Only decoder code is needed, so you can speed up the build
190 slightly by passing --disable-encoders to configure. This
191 shouldn't affect the final size of the executables though,
192 because the linker is able to omit the encoder code anyway.
193
194 - xzdec and lzmadec will never use multithreading capabilities of
195 liblzma. You can avoid dependency on libpthread by passing
196 --disable-threads to configure.
197
198 - There are and will be no translated messages for xzdec and
199 lzmadec, so it is fine to pass also --disable-nls to configure.
200
201 - To select somewhat size-optimized variant of some things in
202 liblzma, pass --enable-small to configure.
203
204 - Tell the compiler to optimize for size instead of speed.
205 E.g. with GCC, put -Os into CFLAGS.
206
207
208 5. Additional documentation
209 ---------------------------
210
211 "make install" copies some additional documentation to $docdir
212 (--docdir in configure). These a copy of the GNU GPL v2, which can
213 be replaced with a symlink if your distro ships with shared copies
214 of the common license texts.
215
216
217 6. Extra files
218 --------------
219
220 The "extra" directory contains some small extra tools or other files.
221 The exact set of extra files can vary between XZ Utils releases. The
222 extra files have only limited use or they are too dangerous to be
223 put directly to $bindir (7z2lzma.sh is a good example, since it can
224 silently create corrupt output if certain conditions are not met).
225
226 If you feel like it, you may copy the extra directory under the doc
227 directory (e.g. /usr/share/doc/xz/extra). Maybe some people will find
228 them useful. However, most people needing these tools probably are
229 able to find them from the source package too.
230
231 The "debug" directory contains some tools that are useful only when
232 hacking on XZ Utils. Don't package these tools.
233
234
235 7. Installing XZ Utils and LZMA Utils in parallel
236 -------------------------------------------------
237
238 XZ Utils and LZMA Utils 4.32.x can be installed in parallel by
239 omitting the compatibility symlinks (lzma, unlzma, lzcat, lzgrep etc.)
240 from the XZ Utils package. It's probably a good idea to still package
241 the symlinks into a separate package so that users may choose if they
242 want to use XZ Utils or LZMA Utils for handling .lzma files.
243
244
245 8. Example
246 ----------
247
248 Here is an example for i686 GNU/Linux that
249 - links xz against static liblzma;
250 - includes only shared liblzma in the final package;
251 - links xzdec and lzmadec against static liblzma while
252 avoiding libpthread dependency.
253
254 PKG=/tmp/xz-pkg
255 tar xf xz-x.y.z.tar.gz
256 cd xz-x.y.z
257 ./configure \
258 --prefix=/usr \
259 --sysconfdir=/etc \
260 CFLAGS='-march=i686 -O2'
261 make
262 make DESTDIR=$PKG install-strip
263 rm -f $PKG/usr/lib/lib*.a
264 sed -i "s/^old_library=.*$/old_library=''/" $PKG/usr/lib/lib*.la
265 make clean
266 ./configure \
267 --prefix=/usr \
268 --sysconfdir=/etc \
269 --disable-shared \
270 --disable-nls \
271 --disable-encoders \
272 --enable-small \
273 --disable-threads \
274 CFLAGS='-march=i686 -Os'
275 make -C src/liblzma
276 make -C src/xzdec
277 make -C src/xzdec DESTDIR=$PKG install-strip
278 cp -a extra $PKG/usr/share/doc/xz
279
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