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.

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-shlibs(5), deb-symbols(5), dpkg-gensymbols(1).

1.19.0.5							    2018-04-16							 dpkg-shlibdeps(1)