<tt><url name="/doc/developers-reference/"
id="http://www.debian.org/doc/developers-reference/"></tt>.
</p>
+
+ <p>
+ Finally, a <qref id="copyrightformat">specification for
+ machine-readable copyright files</qref> is maintained as part of
+ the <package>debian-policy</package> package using the same
+ procedure as the other policy documents. Use of this format is
+ optional.
+ </p>
</sect>
<sect id="definitions">
<item>
must not require or recommend a package outside
of <em>main</em> for compilation or execution (thus, the
- package must not declare a "Depends", "Recommends", or
- "Build-Depends" relationship on a non-<em>main</em>
- package),
+ package must not declare a "Pre-Depends", "Depends",
+ "Recommends", "Build-Depends", or "Build-Depends-Indep"
+ relationship on a non-<em>main</em> package),
</item>
<item>
must not be so buggy that we refuse to support them,
</tag>
<item>
<p>
- A package may also provide both of the targets
+ A package may also provide one or both of the targets
<tt>build-arch</tt> and <tt>build-indep</tt>.
The <tt>build-arch</tt> target, if provided, should
perform all the configuration and compilation required for
architecture-independent binary packages (those packages
for which the body of the <tt>Architecture</tt> field
in <tt>debian/control</tt> is <tt>all</tt>).
- The <tt>build</tt> target should depend on those of the
- targets <tt>build-arch</tt> and <tt>build-indep</tt> that
- are provided in the rules file.<footnote>
+ </p>
+
+ <p>
+ If <tt>build-arch</tt> or <tt>build-indep</tt> targets are
+ provided in the rules file, the <tt>build</tt> target
+ should either depend on those targets or take the same
+ actions as invoking those targets would perform.<footnote>
The intent of this split is so that binary-only builds
need not install the dependencies required for
the <tt>build-indep</tt> target. However, this is not
</p>
<p>
- Each paragraph consists of a series of data fields; each
- field consists of the field name, followed by a colon and
- then the data/value associated with that field. The field
- name is composed of printable ASCII characters (i.e.,
- characters that have values between 33 and 126, inclusive)
- except colon and must not with a begin with #. The
- field ends at the end of the line or at the end of the
- last continuation line (see below). Horizontal whitespace
- (spaces and tabs) may occur immediately before or after the
- value and is ignored there; it is conventional to put a
- single space after the colon. For example, a field might
- be:
+ Each paragraph consists of a series of data fields. Each field
+ consists of the field name followed by a colon and then the
+ data/value associated with that field. The field name is
+ composed of US-ASCII characters excluding control characters,
+ space, and colon (i.e., characters in the ranges 33-57 and
+ 59-126, inclusive). Field names must not begin with the comment
+ character, <tt>#</tt>.
+ </p>
+
+ <p>
+ The field ends at the end of the line or at the end of the last
+ continuation line (see below). Horizontal whitespace (spaces
+ and tabs) may occur immediately before or after the value and is
+ ignored there; it is conventional to put a single space after
+ the colon. For example, a field might be:
<example compact="compact">
Package: libc6
</example>
<p>
This file consists of a single paragraph, possibly surrounded by
a PGP signature. The fields of that paragraph are listed below.
- Their syntax is described above, in <ref id="pkg-controlfields">.
+ Their syntax is described above, in <ref id="controlsyntax">.
<list compact="compact">
<item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
<heading><tt>DM-Upload-Allowed</tt></heading>
<p>
- The most recent version of a package uploaded to unstable or
- experimental must include the field <tt>DM-Upload-Allowed:
- yes</tt> in the source section of its source control file for
- the Debian archive to accept uploads signed with a key in the
- Debian Maintainer keyring. See the General
+ Indicates that Debian Maintainers may upload this package to
+ the Debian archive. The only valid value is <tt>yes</tt>. If
+ the field <tt>DM-Upload-Allowed: yes</tt> is present in the
+ source section of the source control file of the most recent
+ version of a package in unstable or experimental, the Debian
+ archive will accept uploads of this package signed with a key
+ in the Debian Maintainer keyring. See the General
Resolution <url id="http://www.debian.org/vote/2007/vote_003"
name="Endorse the concept of Debian Maintainers"> for more
details.
Relationships may be restricted to a certain set of
architectures. This is indicated in brackets after each
individual package name and the optional version specification.
- The brackets enclose a list of Debian architecture names
+ The brackets enclose a non-empty list of Debian architecture names
in the format described in <ref id="arch-spec">,
separated by whitespace. Exclamation marks may be prepended to
each of the names. (It is not permitted for some names to be
be placed in a package named
<package><var>libraryname</var><var>soversion</var></package>,
where <var>soversion</var> is the version number in
- the <tt>SONAME</tt> of the shared library.
- See <ref id="shlibs"> for detailed information on how to
- determine this version. Alternatively, if it would be confusing
- to directly append <var>soversion</var>
- to <var>libraryname</var> (if, for example, <var>libraryname</var>
- itself ends in a number), you should use
+ the <tt>SONAME</tt> of the shared library. Alternatively, if it
+ would be confusing to directly append <var>soversion</var>
+ to <var>libraryname</var> (if, for
+ example, <var>libraryname</var> itself ends in a number), you
+ should use
<package><var>libraryname</var>-<var>soversion</var></package>
instead.
</p>
+ <p>
+ To determine the <var>soversion</var>, look at
+ the <tt>SONAME</tt> of the library, stored in the
+ ELF <tt>SONAME</tt> attribute. it is usually of the
+ form <tt><var>name</var>.so.<var>major-version</var></tt> (for
+ example, <tt>libz.so.1</tt>). The version part is the part
+ which comes after <tt>.so.</tt>, so in that example it
+ is <tt>1</tt>. The soname may instead be of the
+ form <tt><var>name</var>-<var>major-version</var>.so</tt>, such
+ as <tt>libdb-5.1.so</tt>, in which case the name would
+ be <tt>libdb</tt> and the version would be <tt>5.1</tt>.
+ </p>
+
<p>
If you have several shared libraries built from the same source
tree, you may lump them all together into a single shared
linked against the old shared library. Correct versioning of
dependencies on the newer shared library by binaries that use
the new interfaces is handled via
- the <qref id="sharedlibs-symbols"><tt>symbols</tt> system</qref>
- or the <qref id="sharedlibs-shlibdeps"><tt>shlibs</tt>
- system</qref>.
+ the <qref id="sharedlibs-depends"><tt>symbols</tt>
+ or <tt>shlibs</tt> system</qref>.
</p>
<p>
</p>
</sect>
- <sect id="sharedlibs-symbols">
- <heading>Dependencies between the library and other packages -
- the <tt>symbols</tt> system</heading>
+ <sect id="sharedlibs-depends">
+ <heading>Dependencies between the library and other
+ packages</heading>
<p>
If a package contains a binary or library which links to a
installed on the system, all of the libraries needed are also
installed. These dependencies must be added to the binary
package when it is built, since they may change based on which
- version of a shared library the binary or library was linnked
- with. To allow these dependencies to be constructed, shared
- libraries must provide either a <file>symbols</file> file or
+ version of a shared library the binary or library was linked
+ with even if there are no changes to the source of the binary
+ (for example, symbol versions change, macros become functions or
+ vice versa, or the binary package may determine at compile-time
+ whether new library interfaces are available and can be called).
+ To allow these dependencies to be constructed, shared libraries
+ must provide either a <file>symbols</file> file or
a <file>shlibs</file> file, which provide information on the
package dependencies required to ensure the presence of this
library. Any package which uses a shared library must use these
</p>
<p>
- <file>shlibs</file> files were the original mechanism for
- handling library dependencies. They are documented
- in <ref id="sharedlibs-shlibdeps">. <file>symbols</file> files,
- documented in this section, are recommended for most packages,
- since they provide dependency information for each exported
- symbol and therefore generate more accurate dependencies for
- binaries that do not use symbols from newer versions of the
- shared library. However, <file>shlibs</file> files must be used
- for udebs. Packages which provide a <file>symbols</file> file
- are not required to provide a <file>shlibs</file> file.
+ These two mechanisms differ in the degree of detail that they
+ provide. A <file>symbols</file> file documents every symbol
+ that is part of the library ABI and, for each, the version of
+ the package in which it was introduced. This permits detailed
+ analysis of the symbols used by a particular package and
+ construction of an accurate dependency, but it requires the
+ package maintainer to track more information about the shared
+ library. A <file>shlibs</file> file, in contrast, only
+ documents the last time the library ABI changed in any way. It
+ only provides information about the library as a whole, not
+ individual symbols. When a package is built using a shared
+ library with only a <file>shlibs</file> file, the generated
+ dependency will require a version of the shared library equal to
+ or newer than the version of the last ABI change. This
+ generates unnecessarily restrictive dependencies compared
+ to <file>symbols</file> files if none of the symbols used by the
+ package have changed. This, in turn, may make upgrades
+ needlessly complex and unnecessarily restrict use of the package
+ on systems with older versions of the shared libraries.
</p>
<p>
- When a package that contains any shared libraries or compiled
- binaries is built, it must run <prgn>dpkg-shlibdeps</prgn> on
- each shared library and compiled binary to determine the
- libraries used and hence the dependencies needed by the
- package.<footnote>
- <prgn>dpkg-shlibdeps</prgn> will use a program
- like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find the
- libraries and the symbols in those libraries directly needed
- by the binaries or shared libraries in the package.
- </footnote>
+ <file>shlibs<file> files also have a flawed representation of
+ library SONAMEs, making it difficult to use <file>shlibs</file>
+ files in some unusual corner cases.
</p>
<p>
- We say that a binary <tt>foo</tt> <em>directly</em> uses a
- library <tt>libbar</tt> if it is explicitly linked with that
- library (that is, the library is listed in the
- ELF <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
- to the link line when the binary is created). Other libraries
- that are needed by <tt>libbar</tt> are
- linked <em>indirectly</em> to <tt>foo</tt>, and the dynamic
- linker will load them automatically when it
- loads <tt>libbar</tt>. A package should depend on the libraries
- it directly uses, but not the libraries it indirectly uses. The
- dependencies for those libraries will automatically pull in the
- other libraries. <prgn>dpkg-shlibdeps</prgn> will handle this
- logic automatically, but package maintainers need to be aware of
- this distinction between directly and indirectly using a library
- if they have to override its results for some reason.
- <footnote>
- A good example of where this helps is the following. We could
- update <tt>libimlib</tt> with a new version that supports a
- new graphics format called dgf (but retaining the same major
- version number) and depends on <tt>libdgf</tt>. If we
- used <prgn>ldd</prgn> to add dependencies for every library
- directly or indirectly linked with a binary, every package
- that uses <tt>libimlib</tt> would need to be recompiled so it
- would also depend on <tt>libdgf</tt> or it wouldn't run due to
- missing symbols. Since dependencies are only added based on
- ELF <tt>NEEDED</tt> attribute, packages
- using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
- having the dependency on <tt>libdgf</tt> and so they would not
- need rebuilding.
- </footnote>
+ <file>symbols</file> files are therefore recommended for most
+ shared library packages since they provide more accurate
+ dependencies. For most C libraries, the additional detail
+ required by <file>symbols</file> files is not too difficult to
+ maintain. However, maintaining exhaustive symbols information
+ for a C++ library can be quite onerous, so <file>shlibs</file>
+ files may be more appropriate for most C++ libraries. udebs
+ must also use <file>shlibs</file>, since the udeb infrastructure
+ does not use <file>symbols</file>.
</p>
- <p>
- In the following sections, we will first describe where the
- various <file>symbols</file> files are to be found, then how to
- use <prgn>dpkg-shlibdeps</prgn>, and finally
- the <file>symbols</file> file format and how to create them if
- your package contains a shared library.
- </p>
-
- <sect1 id="symbols-paths">
- <heading>The <file>symbols</file> files present on the
- system</heading>
-
- <p>
- <file>symbols</file> files for a shared library are normally
- provided by the shared library package, but there are several
- override paths that are checked first in case that information
- is wrong or missing. The following list gives them in the
- order in which they are read by <prgn>dpkg-shlibdeps</prgn>
- The first one that contains the required information is used.
- <list>
- <item>
- <p><file>debian/*/DEBIAN/symbols</file></p>
-
- <p>
- During the package build, if the package itself contains
- shared libraries with <file>symbols</file> files, they
- will be generated in these staging directories
- by <prgn>dpkg-gensymbols</prgn>. <file>symbols</file>
- files found in the build tree take precedence
- over <file>symbols</file> files from other binary
- packages.
- </p>
-
- <p>
- These files must exist
- before <prgn>dpkg-shlibdeps</prgn> is run or the
- dependencies of binaries and libraries from a source
- package on other libraries from that same source package
- will not be correct. In practice, this means
- that <prgn>dpkg-gensymbols</prgn> must be run
- before <prgn>dpkg-shlibdeps</prgn> during the package
- build.<footnote>
- An example may clarify. Suppose the source
- package <tt>foo</tt> generates two binary
- packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
- When building the binary packages, the contents of the
- packages are staged in the
- directories <file>debian/libfoo2</file>
- and <file>debian/foo-runtime</file> respectively.
- (<file>debian/tmp</file> could be used instead of one
- of these.) Since <tt>libfoo2</tt> provides
- the <tt>libfoo</tt> shared library, it will contain
- a <tt>symbols</tt> file, which will be installed
- in <file>debian/libfoo2/DEBIAN/symbols</file>,
- eventually to be included as a control file in that
- package. When <prgn>dpkg-shlibdeps</prgn> is run on
- the
- executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
- it will examine
- the <file>debian/libfoo2/DEBIAN/symbols</file> file to
- determine whether <tt>foo-prog</tt>'s library
- dependencies are satisfied by any of the libraries
- provided by <tt>libfoo2</tt>. Since those binaries
- were linked against the just-built shared library as
- part of the build process, the <file>symbols</file>
- file for the newly-built <tt>libfoo2</tt> must take
- precedence over a <file>symbols</file> file for any
- other <tt>libfoo2</tt> package already installed on
- the system.
- </footnote>
- </p>
- </item>
-
- <item>
- <p>
- <file>/etc/dpkg/symbols/<var>package</var>.symbols.<var>arch</var></file>
- and <file>/etc/dpkg/symbols/<var>package</var>.symbols</file>
- </p>
-
- <p>
- Per-system overrides of shared library dependencies.
- These files normally do not exist. They are maintained
- by the local system administrator and must not be
- created by any Debian package.
- </p>
- </item>
-
- <item>
- <p><file>symbols</file> control files for packages
- installed on the system</p>
-
- <p>
- The <file>symbols</file> control files for all the
- packages currently installed on the system are searched
- last. This will be the most common source of shared
- library dependency information. These are normally
- found in <file>/var/lib/dpkg/info/*.symbols</file>, but
- packages should not rely on this and instead should
- use <tt>dpkg-query --control-path <var>package</var>
- symbols</tt> if for some reason these files need to be
- examined.
- </p>
- </item>
- </list>
- </p>
-
- <p>
- Be aware that if a <file>debian/shlibs.local</file> exists in
- the source package, it will override any <file>symbols</file>
- files. This is the only case where a <file>shlibs</file> is
- used despite <file>symbols</file> files being present. See
- <ref id="shlibs-paths"> and <ref id="sharedlibs-shlibdeps">
- for more information.
- </p>
- </sect1>
-
<sect1 id="dpkg-shlibdeps">
- <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
- <tt>symbols</tt> files</heading>
-
- <p>
- If your package contains any compiled binaries or shared
- libraries, put a call to <prgn>dpkg-shlibdeps</prgn> into
+ <heading>Generating dependencies on shared libraries</heading>
+
+ <p>
+ When a package that contains any shared libraries or compiled
+ binaries is built, it must run <prgn>dpkg-shlibdeps</prgn> on
+ each shared library and compiled binary to determine the
+ libraries used and hence the dependencies needed by the
+ package.<footnote>
+ <prgn>dpkg-shlibdeps</prgn> will use a program
+ like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
+ the libraries and the symbols in those libraries directly
+ needed by the binaries or shared libraries in the package.
+ </footnote>
+ To do this, put a call to <prgn>dpkg-shlibdeps</prgn> into
your <file>debian/rules</file> file in the source package.
List all of the compiled binaries, libraries, or loadable
- modules in your package. If your source package builds only a
- single binary package that contains only compiled binaries and
- libraries (but no scripts) and is not multiarch, you can use a
- command such as:
- <example compact="compact">
-dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
- debian/tmp/usr/lib/*
- </example>
- but normally finding all of the binaries is more
- complex.<footnote>
- The easiest way to do this is to use a package helper
- framework such as <tt>debhelper</tt>. If you are
- using <tt>debhelper</tt>, the <prgn>dh_shlibdeps</prgn>
- program will do this work for you. It will also correctly
- handle multi-binary packages.
+ modules in your package.<footnote>
+ The easiest way to call <prgn>dpkg-shlibdeps</prgn>
+ correctly is to use a package helper framework such
+ as <package>debhelper</package>. If you are
+ using <package>debhelper</package>,
+ the <prgn>dh_shlibdeps</prgn> program will do this work for
+ you. It will also correctly handle multi-binary packages.
</footnote>
+ <prgn>dpkg-shlibdeps</prgn> will use the <file>symbols</file>
+ or <file>shlibs</file> files installed by the shared libraries
+ to generate dependency information. The package must then
+ provide a substitution variable into which the discovered
+ dependency information can be placed.
+ </p>
+
+ <p>
+ If you are creating a udeb for use in the Debian Installer,
+ you will need to specify that <prgn>dpkg-shlibdeps</prgn>
+ should use the dependency line of type <tt>udeb</tt> by adding
+ the <tt>-tudeb</tt> option<footnote>
+ <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
+ will automatically add this option if it knows it is
+ processing a udeb.
+ </footnote>. If there is no dependency line of
+ type <tt>udeb</tt> in the <file>shlibs</file>
+ file, <prgn>dpkg-shlibdeps</prgn> will fall back to the
+ regular dependency line.
</p>
<p>
- This command puts the dependency information into
- the <file>debian/substvars</file> file, which is then used
- by <prgn>dpkg-gencontrol</prgn>. You will need to place
- a <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
- field in the control file of every binary package built by
- this source package that contains compiled binaries,
- libraries, or loadable modules. If you have multiple binary
- packages, you will need to call <prgn>dpkg-shlibdeps</prgn> on
- each one which contains compiled libraries or binaries, using
- the <tt>-T</tt> option to the <tt>dpkg</tt> utilities to
- specify a different <file>substvars</file> file for each
- binary package.<footnote>
+ <prgn>dpkg-shlibdeps</prgn> puts the dependency information
+ into the <file>debian/substvars</file> file by default, which
+ is then used by <prgn>dpkg-gencontrol</prgn>. You will need
+ to place a <tt>${shlibs:Depends}</tt> variable in
+ the <tt>Depends</tt> field in the control file of every binary
+ package built by this source package that contains compiled
+ binaries, libraries, or loadable modules. If you have
+ multiple binary packages, you will need to
+ call <prgn>dpkg-shlibdeps</prgn> on each one which contains
+ compiled libraries or binaries, using the <tt>-T</tt> option
+ to the <tt>dpkg</tt> utilities to specify a
+ different <file>substvars</file> file for each binary
+ package.<footnote>
Again, <prgn>dh_shlibdeps</prgn>
- and <prgn>dh_gencontrol</prgn> will handle all of this for
- you if you're using <tt>debhelper</tt>.
+ and <prgn>dh_gencontrol</prgn> will handle everything except
+ the addition of the variable to the control file for you if
+ you're using <package>debhelper</package>, including
+ generating separate <file>substvars</file> files for each
+ binary package and calling <prgn>dpkg-gencontrol</prgn> with
+ the appropriate flags.
</footnote>
</p>
For more details on <prgn>dpkg-shlibdeps</prgn>,
see <manref name="dpkg-shlibdeps" section="1">.
</p>
- </sect1>
-
- <sect1 id="symbols">
- <heading>The <file>symbols</file> File Format</heading>
<p>
- The following documents the format of the <file>symbols</file>
- control file as included in binary packages. These files are
- built from template <file>symbols</file> files in the source
- package by <prgn>dpkg-gensymbols</prgn>. The template files
- support a richer syntax that
- allows <prgn>dpkg-gensymbols</prgn> to do some of the tedious
- work involved in maintaining <file>symbols</file> files, such
- as handling C++ symbols or optional symbols that may not exist
- on particular architectures. When
- writing <file>symbols</file> files for a shared library
- package, refer to <manref name="dpkg-gensymbols" section="1">
- for the richer syntax.
- </p>
-
- <p>
- A <file>symbols</file> may contain one or more entries, one
- for each shared library contained in the package corresponding
- to that <file>symbols</file>. Each entry has the following
- format:
- </p>
-
- <p>
- <example>
-<var>library-soname</var> <var>main-dependency-template</var>
-[ | <var>alternative-dependency-template</var> ]
-[ ... ]
-[ * <var>field-name</var>: <var>field-value</var> ]
-[ ... ]
- <var>symbol</var> <var>minimal-version</var>[ <var>id-of-dependency-template</var> ]
- </example>
- </p>
-
- <p>
- To explain this format, we'll use the the <tt>zlib1g</tt>
- package as an example, which (at the time of writing) installs
- the shared library <file>/usr/lib/libz.so.1.2.3.4</file>.
- Mandatory lines will be described first, followed by optional
- lines.
- </p>
-
- <p>
- <var>library-soname</var> must contain exactly the value of
- the ELF <tt>SONAME</tt> attribute of the shared library. In
- our example, this is <tt>libz.so.1</tt>.<footnote>
- This can be determined by using the command
- <example compact="compact">
-readelf -d /usr/lib/libz.so.1.2.3.4 | grep SONAME
- </example>
+ We say that a binary <tt>foo</tt> <em>directly</em> uses a
+ library <tt>libbar</tt> if it is explicitly linked with that
+ library (that is, the library is listed in the
+ ELF <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
+ to the link line when the binary is created). Other libraries
+ that are needed by <tt>libbar</tt> are
+ linked <em>indirectly</em> to <tt>foo</tt>, and the dynamic
+ linker will load them automatically when it
+ loads <tt>libbar</tt>. A package should depend on the
+ libraries it directly uses, but not the libraries it
+ indirectly uses. The dependencies for the libraries used
+ directly will automatically pull in the indirectly-used
+ libraries. <prgn>dpkg-shlibdeps</prgn> will handle this logic
+ automatically, but package maintainers need to be aware of
+ this distinction between directly and indirectly using a
+ library if they have to override its results for some reason.
+ <footnote>
+ A good example of where this helps is the following. We
+ could update <tt>libimlib</tt> with a new version that
+ supports a new revision of a graphics format called dgf (but
+ retaining the same major version number) and depends on a
+ new library package <package>libdgf4</package> instead of
+ the older <package>libdgf3</package>. If we
+ used <prgn>ldd</prgn> to add dependencies for every library
+ directly or indirectly linked with a binary, every package
+ that uses <tt>libimlib</tt> would need to be recompiled so
+ it would also depend on <package>libdgf4</package> in order
+ to retire the older <package>libdgf3</package> package.
+ Since dependencies are only added based on
+ ELF <tt>NEEDED</tt> attribute, packages
+ using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
+ having the dependency on an appropriate version
+ of <tt>libdgf</tt> and do not need rebuilding.
</footnote>
</p>
+ </sect1>
- <p>
- <var>main-dependency-template</var> has the same syntax as a
- dependency field in a binary package control file, except that
- the string <tt>#MINVER#</tt> is replaced by a version
- restriction like <tt>(>= <var>version</var>)</tt> or by
- nothing if an unversioned dependency is deemed sufficient.
- The version restriction will be based on which symbols from
- the shared library are referenced and the version at which
- they were introduced (see below). In nearly all
- cases, <var>main-dependency-template</var> will
- be <tt><var>package</var> #MINVER#</tt>,
- where <var>package</var> is the name of the binary package
- containing the shared library. This adds a simple,
- possibly-versioned dependency on the shared library package.
- In some rare cases, such as when multiple packages provide the
- same shared library ABI, the dependency template may need to
- be more complex.
- </p>
+ <sect1 id="sharedlibs-updates">
+ <heading>Shared library ABI changes</heading>
<p>
- In our example, the first line of
- the <tt>zlib1g</tt> <file>symbols</file> file would be:
- <example compact="compact">
-libz.so.1 zlib1g #MINVER#
- </example>
+ Maintaining a shared library package using
+ either <file>symbols</file> or <file>shlibs</file> files
+ requires being aware of the exposed ABI of the shared library
+ and any changes to it. Both <file>symbols</file>
+ and <file>shlibs</file> files record every change to the ABI
+ of the shared library; <file>symbols</file> files do so per
+ public symbol, whereas <file>shlibs</file> files record only
+ the last change for the entire library.
</p>
<p>
- Each public symbol exported by the shared library must have a
- corresponding symbol line, indented by one
- space. <var>symbol</var> is the exported symbol (which, for
- C++, means the mangled symbol) followed by <tt>@</tt> and the
- symbol version, or the string <tt>Base</tt> if there is no
- symbol version. <var>minimal-version</var> is the most recent
- version of the shared library that changed the behavior of
- that symbol, whether by adding it, changing its function
- signature (the parameters, their types, or the return type),
- or its behavior in a way that is visible to a
- caller. <var>id-of-dependency-template</var> is an optional
- field that references
- an <var>alternative-dependency-template</var>; see below for a
- full description.
- </p>
-
- <p>
- For example, <tt>libz.so.1</tt> contains the
- symbols <tt>compress</tt>
- and <tt>compressBound</tt>. <tt>compress</tt> has no symbol
- version and last changed its behavior in upstream
- version <tt>1:1.1.4</tt>. <tt>compressBound</tt> has the
- symbol version <tt>ZLIB_1.2.0</tt>, was introduced in upstream
- version <tt>1:1.2.0</tt>, and has not changed its behavior.
- Its <file>symbols</file> file therefore contains the lines:
- <example compact="compact">
- compress@Base 1:1.1.4
- compressBound@ZLIB_1.2.0 1:1.2.0
- </example>
- Packages using only <tt>compress</tt> would then get a
- dependency of <tt>zlib1g (>= 1:1.1.4)</tt>, but packages
- using <tt>compressBound</tt> would get a dependency
- of <tt>zlib1g (>= 1:1.2.0)</tt>.
- </p>
-
- <p>
- One or more <var>alternative-dependency-template</var> lines
- may be provided. These are used in cases where some symbols
- in the shared library should use one dependency template while
- others should use a different template. The alternative
- dependency templates are used only if a symbol line contains
- the <var>id-of-dependency-template</var> field. The first
- alternative dependency template is numbered 1, the second 2,
- and so forth.<footnote>
- An example of where this may be needed is with a library
- that implements the libGL interface. All GL implementations
- provide the same set of base interfaces, and then may
- provide some additional interfaces only used by programs
- that require that specific GL implementation. So, for
- example, libgl1-mesa-glx may use the
- following <file>symbols</file> file:
- <example>
-libGL.so.1 libgl1
-| libgl1-mesa-glx #MINVER#
- publicGlSymbol@Base 6.3-1
- [...]
- implementationSpecificSymbol@Base 6.5.2-7 1
- [...]
- </example>
- Binaries or shared libraries using
- only <tt>publicGlSymbol</tt> would depend only
- on <tt>libgl1</tt> (which may be provided by multiple
- packages), but ones
- using <tt>implementationSpecificSymbol</tt> would get a
- dependency on <tt>libgl1-mesa-glx (>= 6.5.2-7)</tt>
- </footnote>
- </p>
-
- <p>
- Finally, the entry for the library may contain one or more
- metadata fields. Currently, the only
- supported <var>field-name</var>
- is <tt>Build-Depends-Package</tt>, whose value lists
- the <qref id="sharedlibs-dev">library development
- package</qref> on which packages using this shared library
- declare a build dependency. If this field is
- present, <prgn>dpkg-shlibdeps</prgn> uses it to ensure that
- the resulting binary package dependency on the shared library
- is at least as strict as the source package dependency on the
- shared library development package.<footnote>
- This field should normally not be necessary, since if the
- behavior of any symbol has changed, the corresponding
- symbol <var>minimal-version</var> should have been
- increased. But including it makes the <tt>symbols</tt>
- system more robust by tightening the dependency in cases
- where the package using the shared library specifically
- requires at least a particular version of the shared library
- development package for some reason.
- </footnote>
- For our example, the <tt>zlib1g</tt> <file>symbols</file> file
- would contain:
- <example compact="compact">
- * Build-Depends-Package: zlib1g-dev
- </example>
- (Don't forget the leading space.)
+ There are two types of ABI changes: ones that are
+ backward-compatible and ones that are not. An ABI change is
+ backward-compatible if any binary was linked with the previous
+ version of the shared library will still work correctly with
+ the new version of the shared library. Adding new symbols to
+ the shared library is a backward-compatible change. Removing
+ symbols from the shared library is not. Changing the behavior
+ of a symbol may or may not be backward-compatible depending on
+ the change; for example, changing a function to accept a new
+ enum constant not previously used by the library is generally
+ backward-compatible, but changing the members of a struct that
+ is passed into library functions is generally not unless the
+ library takes special precautions to accept old versions of
+ the data structure.
</p>
<p>
- Also see <manref name="deb-symbols" section="5">.
- </p>
- </sect1>
-
- <sect1 id="providing-symbols">
- <heading>Providing a <file>symbols</file> file</heading>
-
- <p>
- If your package provides a shared library, you should arrange
- to include a <file>symbols</file> control file following the
- format described above in that package. You must include
- either a <file>symbols</file> control file or
- a <file>shlibs</file> control file.
- </p>
-
- <p>
- Normally, this is done by creating a <file>symbols</file> in
- the source package
- named <file>debian/<var>package</var>.symbols</file>
- or <file>debian/symbols</file>, possibly
- with <file>.<var>arch</var></file> appended if the symbols
- information varies by architecture. This file may use the
- extended syntax documented
- in <manref name="dpkg-gensymbols" section="1">. Then,
- call <prgn>dpkg-gensymbols</prgn> as part of the package build
- process. It will create <file>symbols</file> files in the
- package staging area based on the binaries and libraries in
- the package staging area and the <file>symbols</file> files in
- the source package.<footnote>
- If you are
- using <tt>debhelper</tt>, <prgn>dh_makeshlibs</prgn> will
- take care of calling either <prgn>dpkg-gensymbols</prgn>
- or generating a <file>shlibs</file> file as appropriate.
- </footnote>
+ ABI changes that are not backward-compatible normally require
+ changing the <tt>SONAME</tt> of the library and therefore the
+ shared library package name, which forces rebuilding all
+ packages using that shared library to update their
+ dependencies and allow them to use the new version of the
+ shared library. For more information,
+ see <ref id="sharedlibs-runtime">. The remainder of this
+ section will deal with backward-compatible changes.
</p>
<p>
- Packages that provide <file>symbols</file> files must keep
- them up-to-date to ensure correct dependencies in packages
- that use the shared libraries. This means updating
- the <file>symbols</file> file whenever a new public symbol is
- added, changing the <var>minimal-version</var> field whenever
- a symbol changes behavior or signature, and changing
- the <var>library-soname</var>
- and <var>main-dependency-template</var>, and probably all of
- the <var>minimal-version</var> fields, when the library
- changes <tt>SONAME</tt>. Removing a public symbol from
- the <file>symbols</file> file because it's no longer provided
- by the library normally requires changing the <tt>SONAME</tt>
- of the library. See <ref id="sharedlibs-runtime">.
+ Backward-compatible changes require either updating or
+ recording the <var>minimal-version</var> for that symbol
+ in <file>symbols</file> files or updating the version in
+ the <var>dependencies</var> in <file>shlibs</file> files. For
+ more information on how to do this in the two formats, see
+ <ref id="symbols"> and <ref id="shlibs">. Below are general
+ rules that apply to both files.
</p>
<p>
- Special care should be taken in updating
- the <var>minimal-version</var> field when the behavior of a
- public symbol changes. This is easy to neglect, since there
- is no automated method of determining such changes, but
- failing to update <var>minimal-version</var> in this case may
+ The easy case is when a public symbol is added. Simply add
+ the version at which the symbol was introduced
+ (for <file>symbols</file> files) or update the dependency
+ version (for <file>shlibs</file>) files. But special care
+ should be taken to update dependency versions when the
+ behavior of a public symbol changes. This is easy to neglect,
+ since there is no automated method of determining such
+ changes, but failing to update versions in this case may
result in binary packages with too-weak dependencies that will
fail at runtime, possibly in ways that can cause security
vulnerabilities. If the package maintainer believes that a
symbol behavior change may have occurred but isn't sure, it's
- safer to update the <var>minimal-version</var> of all possibly
- affected symbols to the current upstream version rather than
- leave them unmodified. This may result in unnecessarily
- strict dependencies, but it ensures that packages whose
- dependencies are satisfied will work properly.
+ safer to update the version rather than leave it unmodified.
+ This may result in unnecessarily strict dependencies, but it
+ ensures that packages whose dependencies are satisfied will
+ work properly.
</p>
<p>
- A common example of when a change
- to <var>minimal-version</var> is required is a function that
- takes an enum or struct argument that controls what the
- function does. For example:
+ A common example of when a change to the is required is a
+ function that takes an enum or struct argument that controls
+ what the function does. For example:
<example>
-enum library_op { OP_FOO, OP_BAR };
-int library_do_operation(enum library_op);
+ enum library_op { OP_FOO, OP_BAR };
+ int library_do_operation(enum library_op);
</example>
If a new operation, <tt>OP_BAZ</tt>, is added,
the <var>minimal-version</var>
- of <tt>library_do_operation</tt> must be increased to the
+ of <tt>library_do_operation</tt> (for <file>symbols</file>
+ files) or the version in the dependency for the shared library
+ (for <file>shlibs</file> files) must be increased to the
version at which <tt>OP_BAZ</tt> was introduced. Otherwise, a
binary built against the new version of the library (having
detected at compile-time that the library
</p>
<p>
- The <var>minimal-version</var> field normally should not
- contain the Debian revision of the package, since the library
- behavior is normally fixed for a particular upstream version
- and any Debian packaging of that upstream version will have
- the same behavior. In the rare case that the library behavior
- was changed in a particular Debian revision,
- appending <tt>~</tt> to the end of
- the <var>minimal-version</var> that includes the Debian
- revision is recommended, since this allows backports of the
- shared library package using the normal backport versioning
- convention to satisfy the dependency.
+ Dependency versions in either <file>symbols</file>
+ or <file>shlibs</file> files normally should not contain the
+ Debian revision of the package, since the library behavior is
+ normally fixed for a particular upstream version and any
+ Debian packaging of that upstream version will have the same
+ behavior. In the rare case that the library behavior was
+ changed in a particular Debian revision, appending <tt>~</tt>
+ to the end of the version that includes the Debian revision is
+ recommended, since this allows backports of the shared library
+ package using the normal backport versioning convention to
+ satisfy the dependency.
</p>
</sect1>
- </sect>
- <sect id="sharedlibs-shlibdeps">
- <heading>Dependencies between the library and other packages -
- the <tt>shlibs</tt> system</heading>
+ <sect1 id="sharedlibs-symbols">
+ <heading>The <tt>symbols</tt> system</heading>
- <p>
- The <tt>shlibs</tt> system is an alternative to
- the <tt>symbols</tt> system for declaring dependencies for
- shared libraries. It predated the <tt>symbols</tt> system and
- is therefore frequently seen in older packages. It is also
- required for udebs, which do not support <tt>symbols</tt>.
- </p>
+ In the following sections, we will first describe where the
+ various <file>symbols</file> files are to be found, then
+ the <file>symbols</file> file format, and finally how to
+ create <file>symbols</file> files if your package contains a
+ shared library.
+ </p>
- <p>
- <file>shlibs</file> files do not provide as detailed of
- information as <file>symbols</file> files. They only provide
- information about the library as a whole, not individual
- symbols, and therefore have to force tighter dependencies since
- they have no way of relaxing dependencies for binaries and
- libraries that only use symbols whose behavior has not changed.
- Because of this, and because of some problems with
- how <file>shlibs</file> files represent the
- library <tt>SONAME</tt>, <file>symbols</file> files are
- recommended instead for any shared library package that isn't a
- udeb.
- </p>
+ <sect2 id="symbols-paths">
+ <heading>The <file>symbols</file> files present on the
+ system</heading>
- <p>
- In the following sections, we will first describe where the
- various <file>shlibs</file> files are to be found, then how to
- use <prgn>dpkg-shlibdeps</prgn>, and finally
- the <file>shlibs</file> file format and how to create them if
- your package contains a shared library. Much of the information
- about <file>shlibs</file> files is the same as
- for <file>symbols</file> files, so only the differences will be
- mentioned.
- </p>
+ <p>
+ <file>symbols</file> files for a shared library are normally
+ provided by the shared library package, but there are
+ several override paths that are checked first in case that
+ information is wrong or missing. The following list gives
+ them in the order in which they are read
+ by <prgn>dpkg-shlibdeps</prgn> The first one that contains
+ the required information is used.
+ <list>
+ <item>
+ <p><file>debian/*/DEBIAN/symbols</file></p>
+
+ <p>
+ During the package build, if the package itself
+ contains shared libraries with <file>symbols</file>
+ files, they will be generated in these staging
+ directories by <prgn>dpkg-gensymbols</prgn>
+ (see <ref id="providing-symbols">). <file>symbols</file>
+ files found in the build tree take precedence
+ over <file>symbols</file> files from other binary
+ packages.
+ </p>
+
+ <p>
+ These files must exist
+ before <prgn>dpkg-shlibdeps</prgn> is run or the
+ dependencies of binaries and libraries from a source
+ package on other libraries from that same source
+ package will not be correct. In practice, this means
+ that <prgn>dpkg-gensymbols</prgn> must be run
+ before <prgn>dpkg-shlibdeps</prgn> during the package
+ build.<footnote>
+ An example may clarify. Suppose the source
+ package <tt>foo</tt> generates two binary
+ packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
+ When building the binary packages, the contents of
+ the packages are staged in the
+ directories <file>debian/libfoo2</file>
+ and <file>debian/foo-runtime</file> respectively.
+ (<file>debian/tmp</file> could be used instead of
+ one of these.) Since <tt>libfoo2</tt> provides
+ the <tt>libfoo</tt> shared library, it will contain
+ a <tt>symbols</tt> file, which will be installed
+ in <file>debian/libfoo2/DEBIAN/symbols</file>,
+ eventually to be included as a control file in that
+ package. When <prgn>dpkg-shlibdeps</prgn> is run on
+ the
+ executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
+ it will examine
+ the <file>debian/libfoo2/DEBIAN/symbols</file> file
+ to determine whether <tt>foo-prog</tt>'s library
+ dependencies are satisfied by any of the libraries
+ provided by <tt>libfoo2</tt>. Since those binaries
+ were linked against the just-built shared library as
+ part of the build process, the <file>symbols</file>
+ file for the newly-built <tt>libfoo2</tt> must take
+ precedence over a <file>symbols</file> file for any
+ other <tt>libfoo2</tt> package already installed on
+ the system.
+ </footnote>
+ </p>
+ </item>
- <sect1 id="shlibs-paths">
- <heading>The <file>shlibs</file> files present on the
- system</heading>
+ <item>
+ <p>
+ <file>/etc/dpkg/symbols/<var>package</var>.symbols.<var>arch</var></file>
+ and <file>/etc/dpkg/symbols/<var>package</var>.symbols</file>
+ </p>
+
+ <p>
+ Per-system overrides of shared library dependencies.
+ These files normally do not exist. They are
+ maintained by the local system administrator and must
+ not be created by any Debian package.
+ </p>
+ </item>
- <p>
- There are several places where <tt>shlibs</tt> files are
- found. The following list gives them in the order in which
- they are read by <prgn>dpkg-shlibdeps</prgn>. (The first one
- which gives the required information is used.)
- <list>
- <item>
- <p><file>debian/shlibs.local</file></p>
+ <item>
+ <p><file>symbols</file> control files for packages
+ installed on the system</p>
+
+ <p>
+ The <file>symbols</file> control files for all the
+ packages currently installed on the system are
+ searched last. This will be the most common source of
+ shared library dependency information. These are
+ normally found
+ in <file>/var/lib/dpkg/info/*.symbols</file>, but
+ packages should not rely on this and instead should
+ use <tt>dpkg-query --control-path <var>package</var>
+ symbols</tt> if for some reason these files need to be
+ examined.
+ </p>
+ </item>
+ </list>
+ </p>
- <p>
- This lists overrides for this package. This file should
- normally not be used, but may be needed temporarily in
- unusual situations to work around bugs in other
- packages, or in unusual cases where the normally
- declared dependency information in the
- installed <file>shlibs</file> file for a library cannot
- be used. This file overrides information obtained from
- any other source.
- </p>
- </item>
+ <p>
+ Be aware that if a <file>debian/shlibs.local</file> exists
+ in the source package, it will override
+ any <file>symbols</file> files. This is the only case where
+ a <file>shlibs</file> is used despite <file>symbols</file>
+ files being present. See <ref id="shlibs-paths">
+ and <ref id="sharedlibs-shlibdeps"> for more information.
+ </p>
+ </sect2>
- <item>
- <p><file>/etc/dpkg/shlibs.override</file></p>
+ <sect2 id="symbols">
+ <heading>The <file>symbols</file> File Format</heading>
- <p>
- This lists global overrides. This list is normally
- empty. It is maintained by the local system
- administrator.
- </p>
- </item>
+ <p>
+ The following documents the format of
+ the <file>symbols</file> control file as included in binary
+ packages. These files are built from
+ template <file>symbols</file> files in the source package
+ by <prgn>dpkg-gensymbols</prgn>. The template files support
+ a richer syntax that allows <prgn>dpkg-gensymbols</prgn> to
+ do some of the tedious work involved in
+ maintaining <file>symbols</file> files, such as handling C++
+ symbols or optional symbols that may not exist on particular
+ architectures. When writing <file>symbols</file> files for
+ a shared library package, refer
+ to <manref name="dpkg-gensymbols" section="1"> for the
+ richer syntax.
+ </p>
- <item>
- <p><file>DEBIAN/shlibs</file> files in the "build
- directory"</p>
+ <p>
+ A <file>symbols</file> may contain one or more entries, one
+ for each shared library contained in the package
+ corresponding to that <file>symbols</file>. Each entry has
+ the following format:
+ </p>
- <p>
- When packages are being built,
- any <file>debian/shlibs</file> files are copied into the
- control information file area of the temporary build
- directory and given the name <file>shlibs</file>. These
- files give details of any shared libraries included in
- the same package.
- </p>
- </item>
+ <p>
+ <example>
+ <var>library-soname</var> <var>main-dependency-template</var>
+ [| <var>alternative-dependency-template</var>]
+ [...]
+ [* <var>field-name</var>: <var>field-value</var>]
+ [...]
+ <var>symbol</var> <var>minimal-version</var>[ <var>id-of-dependency-template</var> ]
+ </example>
+ </p>
- <item>
- <p><file>shlibs</file> control files for packages
- installed on the system</p>
+ <p>
+ To explain this format, we'll use the the <tt>zlib1g</tt>
+ package as an example, which (at the time of writing)
+ installs the shared
+ library <file>/usr/lib/libz.so.1.2.3.4</file>. Mandatory
+ lines will be described first, followed by optional lines.
+ </p>
- <p>
- The <file>shlibs</file> control files for all the
- packages currently installed on the system. These are
- normally found
- in <file>/var/lib/dpkg/info/*.symbols</file>, but
- packages should not rely on this and instead should
- use <tt>dpkg-query --control-path <var>package</var>
- shlibs</tt> if for some reason these files need to be
- examined.
- </p>
- </item>
+ <p>
+ <var>library-soname</var> must contain exactly the value of
+ the ELF <tt>SONAME</tt> attribute of the shared library. In
+ our example, this is <tt>libz.so.1</tt>.<footnote>
+ This can be determined by using the command
+ <example compact="compact">
+ readelf -d /usr/lib/libz.so.1.2.3.4 | grep SONAME
+ </example>
+ </footnote>
+ </p>
- <item>
- <p><file>/etc/dpkg/shlibs.default</file></p>
+ <p>
+ <var>main-dependency-template</var> has the same syntax as a
+ dependency field in a binary package control file, except
+ that the string <tt>#MINVER#</tt> is replaced by a version
+ restriction like <tt>(>= <var>version</var>)</tt> or by
+ nothing if an unversioned dependency is deemed sufficient.
+ The version restriction will be based on which symbols from
+ the shared library are referenced and the version at which
+ they were introduced (see below). In nearly all
+ cases, <var>main-dependency-template</var> will
+ be <tt><var>package</var> #MINVER#</tt>,
+ where <var>package</var> is the name of the binary package
+ containing the shared library. This adds a simple,
+ possibly-versioned dependency on the shared library package.
+ In some rare cases, such as when multiple packages provide
+ the same shared library ABI, the dependency template may
+ need to be more complex.
+ </p>
- <p>
- This file lists any shared libraries whose packages have
- failed to provide correct <file>shlibs</file> files. It
- was used when the <file>shlibs</file> setup was first
- introduced, but it is now normally empty. It is
- maintained by the <tt>dpkg</tt> maintainer.
- </p>
- </item>
- </list>
- </p>
+ <p>
+ In our example, the first line of
+ the <tt>zlib1g</tt> <file>symbols</file> file would be:
+ <example compact="compact">
+ libz.so.1 zlib1g #MINVER#
+ </example>
+ </p>
- <p>
- If a <file>symbols</file> file for a shared library package
- is available, <prgn>dpkg-shlibdeps</prgn> will always use it
- in preference to a <file>shlibs</file>, with the exception
- of <file>debian/shlibs.local</file>. The latter overrides any
- other <file>shlibs</file> or <file>symbols</file> files.
- </p>
- </sect1>
+ <p>
+ Each public symbol exported by the shared library must have
+ a corresponding symbol line, indented by one
+ space. <var>symbol</var> is the exported symbol (which, for
+ C++, means the mangled symbol) followed by <tt>@</tt> and
+ the symbol version, or the string <tt>Base</tt> if there is
+ no symbol version. <var>minimal-version</var> is the most
+ recent version of the shared library that changed the
+ behavior of that symbol, whether by adding it, changing its
+ function signature (the parameters, their types, or the
+ return type), or its behavior in a way that is visible to a
+ caller. <var>id-of-dependency-template</var> is an optional
+ field that references
+ an <var>alternative-dependency-template</var>; see below for
+ a full description.
+ </p>
- <sect1>
- <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
- <file>shlibs</file> files</heading>
+ <p>
+ For example, <tt>libz.so.1</tt> contains the
+ symbols <tt>compress</tt>
+ and <tt>compressBound</tt>. <tt>compress</tt> has no symbol
+ version and last changed its behavior in upstream
+ version <tt>1:1.1.4</tt>. <tt>compressBound</tt> has the
+ symbol version <tt>ZLIB_1.2.0</tt>, was introduced in
+ upstream version <tt>1:1.2.0</tt>, and has not changed its
+ behavior. Its <file>symbols</file> file therefore contains
+ the lines:
+ <example compact="compact">
+ compress@Base 1:1.1.4
+ compressBound@ZLIB_1.2.0 1:1.2.0
+ </example>
+ Packages using only <tt>compress</tt> would then get a
+ dependency of <tt>zlib1g (>= 1:1.1.4)</tt>, but packages
+ using <tt>compressBound</tt> would get a dependency
+ of <tt>zlib1g (>= 1:1.2.0)</tt>.
+ </p>
- <p>
- Use of <prgn>dpkg-shlibdeps</prgn> with <file>shlibs</file>
- files is generally the same as with <file>symbols</file>
- files. See <ref id="dpkg-shlibdeps">.
- </p>
+ <p>
+ One or more <var>alternative-dependency-template</var> lines
+ may be provided. These are used in cases where some symbols
+ in the shared library should use one dependency template
+ while others should use a different template. The
+ alternative dependency templates are used only if a symbol
+ line contains the <var>id-of-dependency-template</var>
+ field. The first alternative dependency template is
+ numbered 1, the second 2, and so forth.<footnote>
+ An example of where this may be needed is with a library
+ that implements the libGL interface. All GL
+ implementations provide the same set of base interfaces,
+ and then may provide some additional interfaces only used
+ by programs that require that specific GL implementation.
+ So, for example, libgl1-mesa-glx may use the
+ following <file>symbols</file> file:
+ <example>
+ libGL.so.1 libgl1
+ | libgl1-mesa-glx #MINVER#
+ publicGlSymbol@Base 6.3-1
+ [...]
+ implementationSpecificSymbol@Base 6.5.2-7 1
+ [...]
+ </example>
+ Binaries or shared libraries using
+ only <tt>publicGlSymbol</tt> would depend only
+ on <tt>libgl1</tt> (which may be provided by multiple
+ packages), but ones
+ using <tt>implementationSpecificSymbol</tt> would get a
+ dependency on <tt>libgl1-mesa-glx (>= 6.5.2-7)</tt>
+ </footnote>
+ </p>
- <p>
- If you are creating a udeb for use in the Debian Installer,
- you will need to specify that <prgn>dpkg-shlibdeps</prgn>
- should use the dependency line of type <tt>udeb</tt> by
- adding the <tt>-tudeb</tt> option<footnote>
- <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
- will automatically add this option if it knows it is
- processing a udeb.
- </footnote>. If there is no dependency line of
- type <tt>udeb</tt> in the <file>shlibs</file>
- file, <prgn>dpkg-shlibdeps</prgn> will fall back to the
- regular dependency line.
- </p>
+ <p>
+ Finally, the entry for the library may contain one or more
+ metadata fields. Currently, the only
+ supported <var>field-name</var>
+ is <tt>Build-Depends-Package</tt>, whose value lists
+ the <qref id="sharedlibs-dev">library development
+ package</qref> on which packages using this shared library
+ declare a build dependency. If this field is
+ present, <prgn>dpkg-shlibdeps</prgn> uses it to ensure that
+ the resulting binary package dependency on the shared
+ library is at least as strict as the source package
+ dependency on the shared library development
+ package.<footnote>
+ This field should normally not be necessary, since if the
+ behavior of any symbol has changed, the corresponding
+ symbol <var>minimal-version</var> should have been
+ increased. But including it makes the <tt>symbols</tt>
+ system more robust by tightening the dependency in cases
+ where the package using the shared library specifically
+ requires at least a particular version of the shared
+ library development package for some reason.
+ </footnote>
+ For our example, the <tt>zlib1g</tt> <file>symbols</file>
+ file would contain:
+ <example compact="compact">
+ * Build-Depends-Package: zlib1g-dev
+ </example>
+ </p>
+
+ <p>
+ Also see <manref name="deb-symbols" section="5">.
+ </p>
+ </sect2>
+
+ <sect2 id="providing-symbols">
+ <heading>Providing a <file>symbols</file> file</heading>
+
+ <p>
+ If your package provides a shared library, you should
+ arrange to include a <file>symbols</file> control file
+ following the format described above in that package. You
+ must include either a <file>symbols</file> control file or
+ a <file>shlibs</file> control file.
+ </p>
+
+ <p>
+ Normally, this is done by creating a <file>symbols</file> in
+ the source package
+ named <file>debian/<var>package</var>.symbols</file>
+ or <file>debian/symbols</file>, possibly
+ with <file>.<var>arch</var></file> appended if the symbols
+ information varies by architecture. This file may use the
+ extended syntax documented in <manref name="dpkg-gensymbols"
+ section="1">. Then, call <prgn>dpkg-gensymbols</prgn> as
+ part of the package build process. It will
+ create <file>symbols</file> files in the package staging
+ area based on the binaries and libraries in the package
+ staging area and the <file>symbols</file> files in the
+ source package.<footnote>
+ If you are
+ using <tt>debhelper</tt>, <prgn>dh_makeshlibs</prgn> will
+ take care of calling either <prgn>dpkg-gensymbols</prgn>
+ or generating a <file>shlibs</file> file as appropriate.
+ </footnote>
+ </p>
+
+ <p>
+ Packages that provide <file>symbols</file> files must keep
+ them up-to-date to ensure correct dependencies in packages
+ that use the shared libraries. This means updating
+ the <file>symbols</file> file whenever a new public symbol
+ is added, changing the <var>minimal-version</var> field
+ whenever a symbol changes behavior or signature in a
+ backward-compatible way (see <ref id="sharedlibs-updates">),
+ and changing the <var>library-soname</var>
+ and <var>main-dependency-template</var>, and probably all of
+ the <var>minimal-version</var> fields, when the library
+ changes <tt>SONAME</tt>. Removing a public symbol from
+ the <file>symbols</file> file because it's no longer
+ provided by the library normally requires changing
+ the <tt>SONAME</tt> of the library.
+ See <ref id="sharedlibs-runtime"> for more information
+ on <tt>SONAME</tt>s.
+ </p>
+ </sect2>
</sect1>
- <sect1 id="shlibs">
- <heading>The <file>shlibs</file> File Format</heading>
+ <sect1 id="sharedlibs-shlibdeps">
+ <heading>The <tt>shlibs</tt> system</heading>
<p>
- Each <file>shlibs</file> file has the same format. Lines
- beginning with <tt>#</tt> are considered to be comments and
- are ignored. Each line is of the form:
- <example compact="compact">
-[<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
- </example>
+ The <tt>shlibs</tt> system is an simpler alternative to
+ the <tt>symbols</tt> system for declaring dependencies for
+ shared libraries. It may be more appropriate for C++
+ libraries and other cases where tracking individual symbols is
+ too difficult. It predated the <tt>symbols</tt> system and is
+ therefore frequently seen in older packages. It is also
+ required for udebs, which do not support <tt>symbols</tt>.
</p>
<p>
- We will explain this by reference to the example of the
- <tt>zlib1g</tt> package, which (at the time of writing)
- installs the shared
- library <file>/usr/lib/libz.so.1.2.3.4</file>.
+ In the following sections, we will first describe where the
+ various <file>shlibs</file> files are to be found, then how to
+ use <prgn>dpkg-shlibdeps</prgn>, and finally
+ the <file>shlibs</file> file format and how to create them.
</p>
- <p>
- <var>type</var> is an optional element that indicates the type
- of package for which the line is valid. The only type
- currently in use is <tt>udeb</tt>. The colon and space after
- the type are required.
- </p>
+ <sect2 id="shlibs-paths">
+ <heading>The <file>shlibs</file> files present on the
+ system</heading>
- <p>
- <var>library-name</var> is the name of the shared library, in
- this case <tt>libz</tt>. (This must match the name part of
- the soname, see below.)
- </p>
+ <p>
+ There are several places where <tt>shlibs</tt> files are
+ found. The following list gives them in the order in which
+ they are read by <prgn>dpkg-shlibdeps</prgn>. (The first
+ one which gives the required information is used.)
+ <list>
+ <item>
+ <p><file>debian/shlibs.local</file></p>
+
+ <p>
+ This lists overrides for this package. This file
+ should normally not be used, but may be needed
+ temporarily in unusual situations to work around bugs
+ in other packages, or in unusual cases where the
+ normally declared dependency information in the
+ installed <file>shlibs</file> file for a library
+ cannot be used. This file overrides information
+ obtained from any other source.
+ </p>
+ </item>
- <p>
- <var>soname-version</var> is the version part of the
- ELF <tt>SONAME</tt> attribute of the library.
- The <tt>SONAME</tt> is the thing that must exactly match for
- the library to be recognized by the dynamic linker, and is
- usually of the
- form <tt><var>name</var>.so.<var>major-version</var></tt>, in
- our example, <tt>libz.so.1</tt>.
- The version part is the part which comes after
- <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname
- may instead be of the
- form <tt><var>name</var>-<var>major-version</var>.so</tt>,
- such as <tt>libdb-5.1.so</tt>, in which case the name would
- be <tt>libdb</tt> and the version would be <tt>5.1</tt>.
- </p>
+ <item>
+ <p><file>/etc/dpkg/shlibs.override</file></p>
- <p>
- <var>dependencies</var> has the same syntax as a dependency
- field in a binary package control file. It should give
- details of which packages are required to satisfy a binary
- built against the version of the library contained in the
- package. See <ref id="depsyntax"> for details.
- </p>
+ <p>
+ This lists global overrides. This list is normally
+ empty. It is maintained by the local system
+ administrator.
+ </p>
+ </item>
- <p>
- In our example, if the last change to the <tt>zlib1g</tt>
- package that could change behavior for a client of that
- library was in version <tt>1:1.2.3.3.dfsg-1</tt>, then
- the <tt>shlibs</tt> entry for this library could say:
- <example compact="compact">
-libz 1 zlib1g (>= 1:1.2.3.3.dfsg-1)
- </example>
- This version restriction must be new enough that any binary
- built against the current version of the library will work
- with any version of the shared library that satisfies that
- dependency.
- </p>
+ <item>
+ <p><file>DEBIAN/shlibs</file> files in the "build
+ directory"</p>
+
+ <p>
+ These files are generated as part of the package build
+ process and staged for inclusion as control files in
+ the binary packages being built. They provide details
+ of any shared libraries included in the same package.
+ </p>
+ </item>
- <p>
- As zlib1g also provides a udeb containing the shared library,
- there would also be a second line:
- <example compact="compact">
-udeb: libz 1 zlib1g-udeb (>= 1:1.2.3.3.dfsg-1)
- </example>
- </p>
- </sect1>
+ <item>
+ <p><file>shlibs</file> control files for packages
+ installed on the system</p>
+
+ <p>
+ The <file>shlibs</file> control files for all the
+ packages currently installed on the system. These are
+ normally found
+ in <file>/var/lib/dpkg/info/*.symbols</file>, but
+ packages should not rely on this and instead should
+ use <tt>dpkg-query --control-path <var>package</var>
+ shlibs</tt> if for some reason these files need to be
+ examined.
+ </p>
+ </item>
- <sect1>
- <heading>Providing a <file>shlibs</file> file</heading>
+ <item>
+ <p><file>/etc/dpkg/shlibs.default</file></p>
+
+ <p>
+ This file lists any shared libraries whose packages
+ have failed to provide correct <file>shlibs</file>
+ files. It was used when the <file>shlibs</file> setup
+ was first introduced, but it is now normally empty.
+ It is maintained by the <tt>dpkg</tt> maintainer.
+ </p>
+ </item>
+ </list>
+ </p>
- <p>
- If your package provides a shared library, you need to create
- a <file>shlibs</file> file following the format described
- above. It is usual to call this
- file <file>debian/shlibs</file> (but if you have multiple
- binary packages, you might want to call
- it <file>debian/<var>package</var>.shlibs</file> instead).
- Then let <file>debian/rules</file> install it in the control
- information file area:
- <example compact="compact">
-install -m644 debian/shlibs debian/tmp/DEBIAN
- </example>
- or, in the case of a multi-binary package:
- <example compact="compact">
-install -m644 debian/<var>package</var>.shlibs debian/<var>package</var>/DEBIAN/shlibs
- </example>
- An alternative way of doing this is to create
- the <file>shlibs</file> file in the control information file
- area directly from <file>debian/rules</file> without using
- a <file>debian/shlibs</file> file at all,<footnote>
- This is what <prgn>dh_makeshlibs</prgn> in
- the <package>debhelper</package> suite does. If your package
- also has a udeb that provides a shared
- library, <prgn>dh_makeshlibs</prgn> can automatically
- generate the <tt>udeb:</tt> lines if you specify the name of
- the udeb with the <tt>--add-udeb</tt> option.
- </footnote>
- since the <file>debian/shlibs</file> file itself is ignored by
- <prgn>dpkg-shlibdeps</prgn>.
- </p>
+ <p>
+ If a <file>symbols</file> file for a shared library package
+ is available, <prgn>dpkg-shlibdeps</prgn> will always use it
+ in preference to a <file>shlibs</file>, with the exception
+ of <file>debian/shlibs.local</file>. The latter overrides
+ any other <file>shlibs</file> or <file>symbols</file> files.
+ </p>
+ </sect2>
- <p>
- Since <prgn>dpkg-shlibdeps</prgn> reads
- the <file>DEBIAN/shlibs</file> files in all of the binary
- packages being built from this source package, all of
- the <file>DEBIAN/shlibs</file> files should be installed
- before <prgn>dpkg-shlibdeps</prgn> is called on any of the
- binary packages.
- </p>
+ <sect2 id="shlibs">
+ <heading>The <file>shlibs</file> File Format</heading>
+
+ <p>
+ Each <file>shlibs</file> file has the same format. Lines
+ beginning with <tt>#</tt> are considered to be comments and
+ are ignored. Each line is of the form:
+ <example compact="compact">
+ [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
+ </example>
+ </p>
+
+ <p>
+ We will explain this by reference to the example of the
+ <tt>zlib1g</tt> package, which (at the time of writing)
+ installs the shared
+ library <file>/usr/lib/libz.so.1.2.3.4</file>.
+ </p>
+
+ <p>
+ <var>type</var> is an optional element that indicates the
+ type of package for which the line is valid. The only type
+ currently in use is <tt>udeb</tt>. The colon and space
+ after the type are required.
+ </p>
+
+ <p>
+ <var>library-name</var> is the name of the shared library,
+ in this case <tt>libz</tt>. (This must match the name part
+ of the soname, see below.)
+ </p>
+
+ <p>
+ <var>soname-version</var> is the version part of the
+ ELF <tt>SONAME</tt> attribute of the library, determined the
+ same way that the <var>soversion</var> component of the
+ recommended shared library package name is determined.
+ See <ref id="sharedlibs-runtime"> for the details.
+ </p>
+
+ <p>
+ <var>dependencies</var> has the same syntax as a dependency
+ field in a binary package control file. It should give
+ details of which packages are required to satisfy a binary
+ built against the version of the library contained in the
+ package. See <ref id="depsyntax"> for details on the
+ syntax, and <ref id="sharedlibs-updates"> for details on how
+ to maintain the dependency version constraint.
+ </p>
+
+ <p>
+ In our example, if the last change to the <tt>zlib1g</tt>
+ package that could change behavior for a client of that
+ library was in version <tt>1:1.2.3.3.dfsg-1</tt>, then
+ the <tt>shlibs</tt> entry for this library could say:
+ <example compact="compact">
+ libz 1 zlib1g (>= 1:1.2.3.3.dfsg-1)
+ </example>
+ This version restriction must be new enough that any binary
+ built against the current version of the library will work
+ with any version of the shared library that satisfies that
+ dependency.
+ </p>
+
+ <p>
+ As zlib1g also provides a udeb containing the shared
+ library, there would also be a second line:
+ <example compact="compact">
+ udeb: libz 1 zlib1g-udeb (>= 1:1.2.3.3.dfsg-1)
+ </example>
+ </p>
+ </sect2>
+
+ <sect2>
+ <heading>Providing a <file>shlibs</file> file</heading>
+
+ <p>
+ To provide a <file>shlibs</file> file for a shared library
+ binary package, create a <file>shlibs</file> file following
+ the format described above and place it in
+ the <file>DEBIAN</file> directory for that package during
+ the build. It will then be included as a control file for
+ that package<footnote>
+ This is what <prgn>dh_makeshlibs</prgn> in
+ the <package>debhelper</package> suite does. If your
+ package also has a udeb that provides a shared
+ library, <prgn>dh_makeshlibs</prgn> can automatically
+ generate the <tt>udeb:</tt> lines if you specify the name
+ of the udeb with the <tt>--add-udeb</tt> option.
+ </footnote>.
+ </p>
+
+ <p>
+ Since <prgn>dpkg-shlibdeps</prgn> reads
+ the <file>DEBIAN/shlibs</file> files in all of the binary
+ packages being built from this source package, all of
+ the <file>DEBIAN/shlibs</file> files should be installed
+ before <prgn>dpkg-shlibdeps</prgn> is called on any of the
+ binary packages.
+ </p>
+ </sect2>
</sect1>
</sect>
</chapt>
<heading>File System Structure</heading>
<p>
- The location of all installed files and directories must
- comply with the Filesystem Hierarchy Standard (FHS),
- version 2.3, with the exceptions noted below, and except
- where doing so would violate other terms of Debian
- Policy. The following exceptions to the FHS apply:
+ The location of all files and directories must comply with the
+ Filesystem Hierarchy Standard (FHS), version 2.3, with the
+ exceptions noted below, and except where doing so would
+ violate other terms of Debian Policy. The following
+ exceptions to the FHS apply:
<enumlist>
<item>
symlinked there, is relaxed to a recommendation.
</p>
</item>
+ <item>
+ <p>
+ The additional directory <file>/run</file> in the root
+ file system is allowed. <file>/run</file>
+ replaces <file>/var/run</file>, and the
+ subdirectory <file>/run/lock</file>
+ replaces <file>/var/lock</file>, with
+ the <file>/var</file> directories replaced by symlinks
+ for backwards compatibility. <file>/run</file>
+ and <file>/run/lock</file> must follow all of the
+ requirements in the FHS for <file>/var/run</file>
+ and <file>/var/lock</file>, respectively, such as file
+ naming conventions, file format requirements, or the
+ requirement that files be cleared during the boot
+ process. Files and directories residing
+ in <file>/run</file> should be stored on a temporary
+ file system.
+ </p>
+ </item>
<item>
<p>
The following directories in the root filesystem are
though the spool may still be physically located there.
</p>
</sect1>
+
+ <sect1 id="fhs-run">
+ <heading><file>/run</file> and <file>/run/lock</file></heading>
+
+ <p>
+ The directory <file>/run</file> is cleared at boot, normally
+ by being a mount point for a temporary file system. Packages
+ therefore must not assume that any files or directories
+ under <file>/run</file> other than <file>/run/lock</file>
+ exist unless the package has arranged to create those files or
+ directories since the last reboot. Normally, this is done by
+ the package via an init script. See <ref id="writing-init">
+ for more information.
+ </p>
+
+ <p>
+ Packages must not include files or directories
+ under <file>/run</file>, or under the
+ older <file>/var/run</file> and <file>/var/lock</file> paths.
+ The latter paths will normally be symlinks or other
+ redirections to <file>/run</file> for backwards compatibility.
+ </p>
+ </sect1>
</sect>
<sect>
</p>
<p>
- <file>/var/run</file> and <file>/var/lock</file> may be mounted
- as temporary filesystems<footnote>
- For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
- options in <file>/etc/default/rcS</file>.
- </footnote>, so the <file>init.d</file> scripts must handle this
- correctly. This will typically amount to creating any required
- subdirectories dynamically when the <file>init.d</file> script
- is run, rather than including them in the package and relying on
- <prgn>dpkg</prgn> to create them.
+ Files and directories under <file>/run</file>, including ones
+ referred to via the compatibility paths <file>/var/run</file>
+ and <file>/var/lock</file>, are normally stored on a temporary
+ filesystem and are normally not persistent across a reboot.
+ The <file>init.d</file> scripts must handle this correctly.
+ This will typically mean creating any required subdirectories
+ dynamically when the <file>init.d</file> script is run.
+ See <ref id="fhs-run"> for more information.
</p>
</sect1>
must be linked against all libraries that they use symbols from
in the same way that binaries are. This ensures the correct
functioning of the <qref id="sharedlibs-symbols">symbols</qref>
- and <qref id="sharedlibs-shlibdeps">shlibs</qref>
+ and <qref id="sharedlibs-shlibdeps">shlibs</qref>
systems and guarantees that all libraries can be safely opened
with <tt>dlopen()</tt>. Packagers may wish to use the gcc
option <tt>-Wl,-z,defs</tt> when building a shared library.
<p>
You may wish to restrict your script to SUSv3 features plus the
above set when possible so that it may use <file>/bin/sh</file>
- as its interpreter. If your script works with <prgn>dash</prgn>
- (originally called <prgn>ash</prgn>), it probably complies with
- the above requirements, but if you are in doubt, use
- <file>/bin/bash</file>.
+ as its interpreter. Checking your script
+ with <prgn>checkbashisms</prgn> from
+ the <package>devscripts</package> package or running your script
+ with an alternate shell such as <prgn>posh</prgn> may help
+ uncover violations of the above requirements. If in doubt
+ whether a script complies with these requirements,
+ use <file>/bin/bash</file>.
</p>
<p>
You should not use the copyright file as a general <file>README</file>
file. If your package has such a file it should be
installed in <file>/usr/share/doc/<var>package</var>/README</file> or
- <file>README.Debian</file> or some other appropriate place.</p>
+ <file>README.Debian</file> or some other appropriate place.
+ </p>
+
+ <sect1 id="copyrightformat">
+ <heading>Machine-readable copyright information</heading>
+
+ <p>
+ A specification for a standard, machine-readable format
+ for <file>debian/copyright</file> files is maintained as part
+ of the <package>debian-policy</package> package. This
+ document may be found in the <file>copyright-format</file>
+ files in the <package>debian-policy</package> package. It is
+ also available from the Debian web mirrors at
+ <tt><url name="/doc/packaging-manuals/copyright-format/1.0/"
+ id="http://www.debian.org/doc/packaging-manuals/copyright-format/1.0/"></tt>.
+ </p>
+
+ <p>
+ Use of this format is optional.
+ </p>
+ </sect1>
</sect>
<sect>
the <prgn>PATH</prgn> if necessary, and pass its
second and subsequent arguments to the command it
calls. If no <var>root-command</var> is supplied
- then <var>dpkg-buildpackage</var> will take no
- special action to gain root privilege, so that for
- most packages it will have to be invoked as root to
- start with.</p>
+ then <var>dpkg-buildpackage</var> will use
+ the <prgn>fakeroot</prgn> command, which is sufficient
+ to build most packages without actually requiring root
+ privileges.</p>
</item>
<tag><tt>-b</tt>, <tt>-B</tt></tag>
<item>
<prgn>dpkg-genchanges</prgn>.</p>
</sect1>
+ <sect1 id="pkg-dpkg-shlibdeps">
+ <heading>
+ <prgn>dpkg-shlibdeps</prgn> - calculates shared library
+ dependencies
+ </heading>
+
+ <p>
+ See <manref name="dpkg-shlibdeps" section="1">.
+ </p>
+ </sect1>
+
<sect1 id="pkg-dpkg-distaddfile">
<heading>
<prgn>dpkg-distaddfile</prgn> - adds a file to
dpkg-divert --package smailwrapper --remove --rename \
--divert /usr/sbin/smail.real /usr/sbin/smail
fi
- </example> where <tt>1.02-2</tt> is the version at which the
+ </example> where <tt>1.0-2</tt> is the version at which the
diversion was first added to the package. The postrm should not
remove the diversion on upgrades both because there's no reason to
remove the diversion only to immediately re-add it and since the
projects / debian / debian-policy.git / blobdiff