dpkg-shlibdeps - Online in the Cloud

PROGRAM:

NAME

dpkg-shlibdeps - generate shared library substvar dependencies

SYNOPSIS

dpkg-shlibdeps [option...] [-e]executable [option...]

DESCRIPTION

dpkg-shlibdeps calculates shared library dependencies for executables named in its
arguments. The dependencies are added to the substitution variables file debian/substvars
as variable names shlibs:dependency-field where dependency-field is a dependency field
name. Any other variables starting with shlibs: are removed from the file.

dpkg-shlibdeps has two possible sources of information to generate dependency information.
Either symbols files or shlibs files. For each binary that dpkg-shlibdeps analyzes, it
finds out the list of libraries that it's linked with. Then, for each library, it looks
up either the symbols file, or the shlibs file (if the former doesn't exist or if
debian/shlibs.local contains the relevant dependency). Both files are supposed to be
provided by the library package and should thus be available as
/var/lib/dpkg/info/package.symbols or /var/lib/dpkg/info/package.shlibs. The package name
is identified in two steps: find the library file on the system (looking in the same
directories that ld.so would use), then use dpkg -S library-file to lookup the package
providing the library.

Symbols files
Symbols files contain finer-grained dependency information by providing the minimum
dependency for each symbol that the library exports. The script tries to find a symbols
file associated to a library package in the following places (first match is used):

debian/*/DEBIAN/symbols
Shared library information generated by the current build process that also invoked
dpkg-shlibdeps. They are generated by dpkg-gensymbols(1). They are only used if
the library is found in a package's build tree. The symbols file in that build tree
takes precedence over symbols files from other binary packages.

/etc/dpkg/symbols/package.symbols.arch

/etc/dpkg/symbols/package.symbols
Per-system overriding shared library dependency information. arch is the
architecture of the current system (obtained by dpkg-architecture -qDEB_HOST_ARCH).

Output from “dpkg-query --control-path package symbols”
Package-provided shared library dependency information. Unless overridden by
--admindir, those files are located in /var/lib/dpkg.

While scanning the symbols used by all binaries, dpkg-shlibdeps remembers the (biggest)
minimal version needed for each library. At the end of the process, it is able to write
out the minimal dependency for every library used (provided that the information of the
symbols files are accurate).

As a safe-guard measure, a symbols file can provide a Build-Depends-Package meta-
information field and dpkg-shlibdeps will extract the minimal version required by the
corresponding package in the Build-Depends field and use this version if it's higher than
the minimal version computed by scanning symbols.

Shlibs files
Shlibs files associate directly a library to a dependency (without looking at the
symbols). It's thus often stronger than really needed but very safe and easy to handle.

The dependencies for a library are looked up in several places. The first file providing
information for the library of interest is used:

debian/shlibs.local
Package-local overriding shared library dependency information.

/etc/dpkg/shlibs.override
Per-system overriding shared library dependency information.

debian/*/DEBIAN/shlibs
Shared library information generated by the current build process that also invoked
dpkg-shlibdeps. They are only used if the library is found in a package's build
tree. The shlibs file in that build tree takes precedence over shlibs files from
other binary packages.

Output from “dpkg-query --control-path package shlibs”
Package-provided shared library dependency information. Unless overridden by
--admindir, those files are located in /var/lib/dpkg.

/etc/dpkg/shlibs.default
Per-system default shared library dependency information.

The extracted dependencies are then directly used (except if they are filtered out because
they have been identified as duplicate, or as weaker than another dependency).

OPTIONS

dpkg-shlibdeps interprets non-option arguments as executable names, just as if they'd been
supplied as -eexecutable.

-eexecutable
Include dependencies appropriate for the shared libraries required by executable.
This option can be used multiple times.

-ldirectory
Add directory to the list of directories to search for private shared libraries
(since dpkg 1.17.0). This option can be used multiple times.

Note: Use this option instead of setting LD_LIBRARY_PATH, as that environment
variable is used to control the run-time linker and abusing it to set the shared
library paths at build-time can be problematic when cross-compiling for example.

-ddependency-field
Add dependencies to be added to the control file dependency field dependency-field.
(The dependencies for this field are placed in the variable shlibs:dependency-
field.)

The -ddependency-field option takes effect for all executables after the option,
until the next -ddependency-field. The default dependency-field is Depends.

If the same dependency entry (or set of alternatives) appears in more than one of
the recognized dependency field names Pre-Depends, Depends, Recommends, Enhances or
Suggests then dpkg-shlibdeps will automatically remove the dependency from all
fields except the one representing the most important dependencies.

-pvarname-prefix
Start substitution variables with varname-prefix: instead of shlibs:. Likewise,
any existing substitution variables starting with varname-prefix: (rather than
shlibs:) are removed from the the substitution variables file.

-O[filename]
Print substitution variable settings to standard output (or filename if specified,
since dpkg 1.17.2), rather than being added to the substitution variables file
(debian/substvars by default).

-ttype Prefer shared library dependency information tagged for the given package type. If
no tagged information is available, falls back to untagged information. The default
package type is deb. Shared library dependency information is tagged for a given
type by prefixing it with the name of the type, a colon, and whitespace.

-Llocal-shlibs-file
Read overriding shared library dependency information from local-shlibs-file
instead of debian/shlibs.local.

-Tsubstvars-file
Write substitution variables in substvars-file; the default is debian/substvars.

-v Enable verbose mode (since dpkg 1.14.8). Numerous messages are displayed to
explain what dpkg-shlibdeps does.

-xpackage
Exclude the package from the generated dependencies (since dpkg 1.14.8). This is
useful to avoid self-dependencies for packages which provide ELF binaries
(executables or library plugins) using a library contained in the same package.
This option can be used multiple times to exclude several packages.

-Spackage-build-dir
Look into package-build-dir first when trying to find a library (since dpkg
1.14.15). This is useful when the source package builds multiple flavors of the
same library and you want to ensure that you get the dependency from a given binary
package. You can use this option multiple times: directories will be tried in the
same order before directories of other binary packages.

--ignore-missing-info
Do not fail if dependency information can't be found for a shared library (since
dpkg 1.14.8). Usage of this option is discouraged, all libraries should provide
dependency information (either with shlibs files, or with symbols files) even if
they are not yet used by other packages.

--warnings=value
value is a bit field defining the set of warnings that can be emitted by
dpkg-shlibdeps (since dpkg 1.14.17). Bit 0 (value=1) enables the warning “symbol
sym used by binary found in none of the libraries”, bit 1 (value=2) enables the
warning “package could avoid a useless dependency” and bit 2 (value=4) enables the
warning “binary should not be linked against library”. The default value is 3: the
first two warnings are active by default, the last one is not. Set value to 7 if
you want all warnings to be active.

--admindir=dir
Change the location of the dpkg database (since dpkg 1.14.0). The default location
is /var/lib/dpkg.

-?, --help
Show the usage message and exit.

--version
Show the version and exit.

DIAGNOSTICS

Warnings
Since dpkg-shlibdeps analyzes the set of symbols used by each binary of the generated
package, it is able to emit warnings in several cases. They inform you of things that can
be improved in the package. In most cases, those improvements concern the upstream sources
directly. By order of decreasing importance, here are the various warnings that you can
encounter:

symbol sym used by binary found in none of the libraries.
The indicated symbol has not been found in the libraries linked with the binary.
The binary is most likely a library and it needs to be linked with an additional
library during the build process (option -llibrary of the linker).

binary contains an unresolvable reference to symbol sym: it's probably a plugin
The indicated symbol has not been found in the libraries linked with the binary.
The binary is most likely a plugin and the symbol is probably provided by the
program that loads this plugin. In theory a plugin doesn't have any SONAME but this
binary does have one and as such it could not be clearly identified as such.
However the fact that the binary is stored in a non-public directory is a strong
indication that's it's not a normal shared library. If the binary is really a
plugin, then disregard this warning. But there's always the possibility that it's a
real library and that programs linking to it are using an RPATH so that the dynamic
loader finds it. In that case, the library is broken and needs to be fixed.

package could avoid a useless dependency if binary was not linked against library (it uses
none of the library's symbols)
None of the binaries that are linked with library use any of the symbols provided
by the library. By fixing all the binaries, you would avoid the dependency
associated to this library (unless the same dependency is also generated by another
library that is really used).

package could avoid a useless dependency if binaries were not linked against library (they
uses none of the library's symbols)
Exactly the same as the above warning, but for multiple binaries.

binary should not be linked against library (it uses none of the library's symbols)
The binary is linked to a library that it doesn't need. It's not a problem but some
small performance improvements in binary load time can be obtained by not linking
this library to this binary. This warning checks the same information than the
previous one but does it for each binary instead of doing the check globally on all
binaries analyzed.

Errors
dpkg-shlibdeps will fail if it can't find a public library used by a binary or if this
library has no associated dependency information (either shlibs file or symbols file). A
public library has a SONAME and is versioned (libsomething.so.X). A private library (like
a plugin) should not have a SONAME and doesn't need to be versioned.

couldn't find library library-soname needed by binary (its RPATH is 'rpath')
The binary uses a library called library-soname but dpkg-shlibdeps has been unable
to find the library. dpkg-shlibdeps creates a list of directories to check as
following: directories listed in the RPATH of the binary, directories listed in
/etc/ld.so.conf, directories added by the -l option, directories listed in the
LD_LIBRARY_PATH environment variable, and standard public directories (/lib,
/usr/lib, /lib32, /usr/lib32, /lib64, /usr/lib64). Then it checks those directories
in the package's build tree of the binary being analyzed, in the packages' build
trees indicated with the -S command-line option, in other packages' build trees
that contains a DEBIAN/shlibs or DEBIAN/symbols file and finally in the root
directory. If the library is not found in any of those directories, then you get
this error.

If the library not found is in a private directory of the same package, then you
want to add the directory with -l. If it's in another binary package being built,
you want to make sure that the shlibs/symbols file of this package is already
created and that -l contains the appropriate directory if it also is in a private
directory.

no dependency information found for library-file (used by binary).
The library needed by binary has been found by dpkg-shlibdeps in library-file but
dpkg-shlibdeps has been unable to find any dependency information for that library.
To find out the dependency, it has tried to map the library to a Debian package
with the help of dpkg -S library-file. Then it checked the corresponding shlibs
and symbols files in /var/lib/dpkg/info/, and in the various package's build trees
(debian/*/DEBIAN/).

This failure can be caused by a bad or missing shlibs or symbols file in the
package of the library. It might also happen if the library is built within the
same source package and if the shlibs files has not yet been created (in which case
you must fix debian/rules to create the shlibs before calling dpkg-shlibdeps). Bad
RPATH can also lead to the library being found under a non-canonical name (example:
/usr/lib/openoffice.org/../lib/libssl.so.0.9.8 instead of /usr/lib/libssl.so.0.9.8)
that's not associated to any package, dpkg-shlibdeps tries to work around this by
trying to fallback on a canonical name (using realpath(3)) but it might not always
work. It's always best to clean up the RPATH of the binary to avoid problems.

Calling dpkg-shlibdeps in verbose mode (-v) will provide much more information
about where it tried to find the dependency information. This might be useful if
you don't understand why it's giving you this error.

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