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.
- -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
- Print substitution variable settings to standard output,
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. Numerous messages are displayed to
explain what dpkg-shlibdeps does.
- -xpackage
- Exclude the package from the generated dependencies. 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. 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. 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. 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. The
default location is /var/lib/dpkg.
- -?, --help
- Show the usage message and exit.
- --version
- Show the version and exit.
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 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 to LD_LIBRARY_PATH. 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 LD_LIBRARY_PATH 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-shlibs(5),
deb-symbols(5),
dpkg-gensymbols(1).