Provided by: dpkg-dev_1.14.16.6ubuntu3_all bug


       dpkg-gensymbols  -  generate  symbols  files (shared library dependency


       dpkg-gensymbols [options]


       dpkg-gensymbols scans a temporary build tree  (debian/tmp  by  default)
       looking for libraries and generate a symbols file describing them. This
       file, if non-empty, is then installed in the DEBIAN subdirectory of the
       build  tree  so  that it ends up included in the control information of
       the package.

       When generating those files,  it  uses  as  input  some  symbols  files
       provided  by  the maintainer. It looks for the following files (and use
       the first that is found):

       ·   debian/package.symbols.arch

       ·   debian/symbols.arch

       ·   debian/package.symbols

       ·   debian/symbols

       The main interest of those files is  to  provide  the  minimal  version
       associated  to  each  symbol  provided  by  the  libraries.  Usually it
       corresponds to the first version of  that  package  that  provided  the
       symbol, but it can be manually incremented by the maintainer if the ABI
       of the symbol is extended  without  breaking  backwards  compatibility.
       It’s  the  responsibility  of the maintainer to keep those files up-to-
       date and accurate, but dpkg-gensymbols helps him.

       When the generated symbols files differ from  the  maintainer  supplied
       one,  dpkg-gensymbols  will  print  a  diff  between  the two versions.
       Furthermore if the difference are too significant, it  will  even  fail
       (you  can  customize  how  much difference you can tolerate, see the -c


       The symbols files are really useful only if they reflect the  evolution
       of  the  package  through  several releases. Thus the maintainer has to
       update them every  time  that  a  new  symbol  is  added  so  that  its
       associated  minimal version matches reality. To do this properly he can
       use the diffs contained in the build logs.  In  most  cases,  the  diff
       applies directly to his debian/package.symbols file. That said, further
       tweaks are usually needed: it’s recommended for  example  to  drop  the
       Debian revision from the minimal version so that backports with a lower
       version  number  but  the  same  upstream  version  still  satisfy  the
       generated  dependencies.   If  the  Debian  revision  can’t  be dropped
       because the symbol really got added by the Debian specific change, then
       one should suffix the version with "~".

       Before  applying  any  patch to the symbols file, the maintainer should
       double-check that  it’s  sane.  Public  symbols  are  not  supposed  to
       disappear, so the patch should ideally only add new lines.

   Using includes
       When  the set of exported symbols differ between architectures, it’s no
       more possible to  use  a  common  symbols  file.  Using  one  file  per
       architecture works, but it can also lead to duplication of information.
       In those cases, you can factorize the common part in some external file
       and  include  that  file  in your package.symbols.arch file by using an
       include directive like this:

       #include "packages.symbols.common"

       The symbols files are read line by line,  and  include  directives  are
       processed  as soon as they are encountered. This means that the content
       of the included file can override any content that appeared before  the
       include directive and that any content after the directive can override
       anything contained in the included file.

       An included file can repeat the header line containing  the  SONAME  of
       the  library.  In  that  case,  it overrides any header line previously
       read.  However, in general it’s best to avoid duplicating header lines.
       One way to do it is the following:

       #include "libsomething1.symbols.common"
        arch_specific_symbol@Base 1.0

   Using wildcards with versioned symbols
       Well  maintained  libraries  have  versioned symbols where each version
       corresponds to the upstream version where  the  symbol  got  added.  If
       that’s  the  case,  it’s possible to write a symbols file with wildcard
       entries like "*@GLIBC_2.0" that would match any  symbol  associated  to
       the  version GLIBC_2.0. It’s still possible to include specific symbols
       in the file, they’ll take precedence over any matching wildcard  entry.
       An example: libc6 #MINVER#
        *@GLIBC_2.0 2.0
        *@GLIBC_2.7 2.7
        access@GLIBC_2.0 2.2

       The  symbol access@GLIBC_2.0 will lead to a minimal dependency on libc6
       version 2.2 despite the wildcard  entry  *@GLIBC_2.0  which  associates
       symbols versioned as GLIBC_2.0 with the minimal version 2.0.  Note that
       using wildcards means that dpkg-gensymbols can’t check for symbols that
       might   have   disappeared  and  can’t  generate  a  diff  between  the
       maintainer-supplied symbols file and the generated one  in  the  binary

   Good library management
       A well-maintained library has the following features:

       ·   its  API  is  stable  (public  symbols  are never dropped, only new
           public symbols are added) and changes  in  incompatible  ways  only
           when the SONAME changes;

       ·   ideally, it uses symbol versioning to achieve ABI stability despite
           internal changes and API extension;

       ·   it doesn’t export private symbols.

       While maintaining the symbols file, it’s easy to notice appearance  and
       disappearance of symbols. But it’s more difficult to catch incompatible
       API and ABI change. Thus the  maintainer  should  read  thoroughly  the
       upstream  changelog  looking  for cases where the rules of good library
       management have been broken. If potential problems are discovered,  the
       upstream  author should be notified as an upstream fix is always better
       than a Debian specific work-around.


              Scan package-build-dir instead of debian/tmp.

              Define the package  name.  Required  if  more  than  one  binary
              package   is   listed   in  debian/control  (or  if  there’s  no
              debian/control file).

              Define the package version. Defaults to  the  version  extracted
              from  debian/changelog.  Required  if called outside of a source
              package tree.

              Only analyze libraries explicitly listed instead of finding  all
              public  libraries.  You can use a regular expression in library-
              file  to  match  multiple  libraries  with  a  single   argument
              (otherwise you need multiple -e).

              Use filename as reference file to generate the symbols file that
              is integrated in the package itself.

       -O     Print the generated symbols file to standard output, rather than
              being stored in the package build tree.

              Store  the  generated  symbols  file as filename. If filename is
              pre-existing, its content is used as  basis  for  the  generated
              symbols file.  You can use this feature to update a symbols file
              so that it matches a newer upstream version of your library.

              Define the checks to do when  comparing  the  generated  symbols
              file  with the file used as starting point. By default the level
              is 1.  Increasing levels do more checks and include  all  checks
              of  lower levels.  Level 0 disables all checks. Level 1 fails if
              some symbols have disappeared. Level 2 fails if some new symbols
              have  been  introduced.   Level  3  fails if some libraries have
              disappeared.  Level  4  fails  if  some  libraries   have   been

              This  value  can  be  overridden  by  the  environment  variable

       -d     Enable debug mode. Numerous messages are  displayed  to  explain
              what dpkg-gensymbols does.

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

              Show the version and exit.

       deb-symbols(5), dpkg-shlibdeps(1).


       Copyright (C) 2007 Raphaël Hertzog

       This  is free software; see the GNU General Public Licence version 2 or
       later for copying conditions. There is NO WARRANTY.