dpkg-shlibdeps(1) dpkg suite dpkg-shlibdeps(1)
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
Prepend 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
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.
-Ipackage-build-dir
Ignore package-build-dir when looking for shlibs, symbols, and
shared library files (since dpkg 1.18.5). You can use this option
multiple times.
--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.
ENVIRONMENT
DPKG_COLORS
Sets the color mode (since dpkg 1.18.5). The currently accepted
values are: auto (default), always and never.
DPKG_NLS
If set, it will be used to decide whether to activate Native
Language Support, also known as internationalization (or i18n)
support (since dpkg 1.19.0). The accepted values are: 0 and 1
(default).
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 use 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 as 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 added by the -l option,
directories listed in the LD_LIBRARY_PATH environment variable,
cross multiarch directories (ex. /lib/arm64-linux-gnu,
/usr/lib/arm64-linux-gnu), standard public directories (/lib,
/usr/lib), directories listed in /etc/ld.so.conf, and obsolete
multilib directories (/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.
SEE ALSO
deb-substvars(5), deb-shlibs(5), deb-symbols(5), dpkg-gensymbols(1).
1.21.22 2023-05-11 dpkg-shlibdeps(1)
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