libwt requires an explicit link to libboost_signals

[Uqbar]

If you don't link the objects against libboost_signals, you'll get unresolved symbols.
Same sourcecode was working fine without up to Natty.

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: libwt-dev 3.1.10-1build0.1
ProcVersionSignature: Ubuntu 3.0.0-12.19~ppa1-generic-pae-ck 3.0.4-ck1
Uname: Linux 3.0.0-12-generic-pae-ck i686
ApportVersion: 1.23-0ubuntu4
Architecture: i386
Date: Mon Dec 5 17:07:27 2011
InstallationMedia: Kubuntu 11.10 "Oneiric Ocelot" - Release i386 (20111012)
ProcEnviron:
 LANGUAGE=
 LC_COLLATE=C
 PATH=(custom, user)
 LANG=it_IT.UTF-8
 SHELL=/bin/bash
SourcePackage: witty
UpgradeStatus: No upgrade log present (probably fresh install)

[Pau Garcia Quiles (pgquiles)]

How is this a bug in Wt? It looks more like a bug in your application's build system :-? You should never count on a shared library providing third-party symbols.

[Uqbar (uqbar)]

My build system is a command line in a fresh installed Ubuntu.
Something like:
g++ -o application file1.c++ file2.c++ -lwt -lwthttp

[Pau Garcia Quiles (pgquiles)]

Your command line is missing a few -lboost_blahblah

[Pau Garcia Quiles (pgquiles)]

Reporter wrongly assumed Wt libraries would transitively provide third-party symbols.

[Boris (starius)]

Hello!

This is actually a problem of Wt, not of code using Wt.

See test case. It does not use boost.signals directly.

I can compile this test on Ubuntu Natty and Debian Squeeze:

 g++ -lwt -lwthttp 900354.cpp -o 900354

Errors on Ubuntu Lucid (e.g., undefined reference to `boost::signals::detail::slot_base::create_connection()')

Errors on Debian Squeeze with manually built Wt 3.2.0. (undefined reference to symbol 'boost::signals::trackable::~trackable())

I'm suspecting fresh Ubuntu Oneiric to fail. Can anyone test this?

3.2.1-1~natty~pgquiles1: no errors

Natty with ppa https://launchpad.net/~pgquiles/+archive/wt/+build/2618285
no errors

Maybe, it is a bug of some Wt version, not of Debian or Ubuntu packages.

[Pau Garcia Quiles (pgquiles)]

#6

g++ -lwt -lwthttp 900354.cpp -o 900354

is wrong

-l goes at the end:

g++ 900354.cpp -o 900354 -lwt -lwthttp

Please try that and tell me if you still have the problem.

Also, please add the output of:

$ objdump -x /usr/lib/libwt.so
$ objdump -x /usr/lib/libwthttp.so

No need to add everything, I'm only interested in the DT_NEEDED sections, i. e. the first 30 or so lines.

[Boris (starius)]

(only for Debian Squeeze with manually built Wt 3.2.1, Ubuntu Lucid will be latter)

I have tried "g++ 900354.cpp -o 900354 -lwt -lwthttp" -- the same result:

/usr/bin/ld: /tmp/ccB6Voar.o: undefined reference to symbol 'boost::signals::trackable::~trackable()'
/usr/bin/ld: note: 'boost::signals::trackable::~trackable()' is defined in DSO /usr/lib/libboost_signals.so.1.42.0 so try adding it to the linker command line
/usr/lib/libboost_signals.so.1.42.0: could not read symbols: Invalid operation
collect2: ld returned 1 exit status

objdump -x /usr/lib/libwt.so
 NEEDED libboost_thread.so.1.42.0
 NEEDED libboost_regex.so.1.42.0
 NEEDED libboost_signals.so.1.42.0
 NEEDED libboost_system.so.1.42.0
 NEEDED libboost_date_time.so.1.42.0
 NEEDED libssl.so.0.9.8
 NEEDED libcrypto.so.0.9.8
 NEEDED libGraphicsMagick.so.3
 NEEDED libpangoft2-1.0.so.0
 NEEDED libpango-1.0.so.0
 NEEDED libgobject-2.0.so.0
 NEEDED libglib-2.0.so.0
 NEEDED libpthread.so.0
 NEEDED libstdc++.so.6
 NEEDED libm.so.6
 NEEDED libgcc_s.so.1
 NEEDED libc.so.6

objdump -x /usr/lib/libwthttp.so
  NEEDED libwt.so.31
  NEEDED libz.so.1
  NEEDED libssl.so.0.9.8
  NEEDED libcrypto.so.0.9.8
  NEEDED libboost_thread.so.1.42.0
  NEEDED libboost_filesystem.so.1.42.0
  NEEDED libboost_program_options.so.1.42.0
  NEEDED libboost_date_time.so.1.42.0
  NEEDED libpthread.so.0
  NEEDED libboost_regex.so.1.42.0
  NEEDED libboost_signals.so.1.42.0
  NEEDED libboost_system.so.1.42.0
  NEEDED libGraphicsMagick.so.3
  NEEDED libpangoft2-1.0.so.0
  NEEDED libpango-1.0.so.0
  NEEDED libgobject-2.0.so.0
  NEEDED libglib-2.0.so.0
  NEEDED libstdc++.so.6 ...

[Pau Garcia Quiles (pgquiles)]

This is an upstream problem. They are not setting a reduced link interface:

http://techbase.kde.org/Development/CMake_KDE_4_2#New:_The_reduced_link_interface

http://cmake.org/cmake/help/v2.8.8/cmake.html#command:target_link_libraries

I'll talk to upstream and we may work on it this summer but it's definitely not a bug in the packaging.

BTW, 3.2.1 is available from the Wt PPA, as usual:

http://launchpad.net/~pgquiles/+archive/wt/

[Pau Garcia Quiles (pgquiles)]

Hi,

A while ago a bug was reported in Ubuntu:

https://bugs.launchpad.net/ubuntu/+source/witty/+bug/900354

It boils down to this: building an application which uses Wt requires
linking to some libraries (Boost Signals, etc), even if the
application does not directly use them. That can be solved by
establishing a so-called "link interface" for libwt, libwthttp, etc.
It's documented here:

http://techbase.kde.org/Development/CMake_KDE_4_2#New:_The_reduced_link_interface
http://cmake.org/cmake/help/v2.8.8/cmake.html#command:target_link_libraries

I cannot work on this on my (nonexistent) spare time[*] at the moment,
just mentioning the problem and the solution in case other people are
affected.

[*] But of course if someone is interested in sponsoring, do not
hesitate to contact me

--
Pau Garcia i Quiles
http://www.elpauer.org
(Due to my workload, I may need 10 days to answer)

[Boris (starius)]

On Ubuntu Oneiric (fresh install with Universe repo enabled):

/usr/bin/ld: /tmp/ccDHQ6ub.o: undefined reference to symbol 'boost::signals::trackable::~trackable()'
/usr/bin/ld: note: 'boost::signals::trackable::~trackable()' is defined in DSO /usr/lib/libboost_signals.so.1.46.1 so try adding it to the linker command line
/usr/lib/libboost_signals.so.1.46.1: could not read symbols: Invalid operation
collect2: ld returned 1 exit status

objdump -x /usr/lib/libwt.so
  NEEDED libboost_thread.so.1.46.1
  NEEDED libboost_regex.so.1.46.1
  NEEDED libboost_signals.so.1.46.1
  NEEDED libboost_system.so.1.46.1
  NEEDED libboost_date_time.so.1.46.1
  NEEDED libboost_filesystem.so.1.46.1
  NEEDED libhpdf-2.1.0.so
  NEEDED libGraphicsMagick.so.3
  NEEDED libpthread.so.0
  NEEDED libstdc++.so.6
  NEEDED libm.so.6
  NEEDED libgcc_s.so.1
  NEEDED libc.so.6

objdump -x /usr/lib/libwthttp.so
  NEEDED libwt.so.29
  NEEDED libz.so.1
  NEEDED libssl.so.1.0.0
  NEEDED libcrypto.so.1.0.0
  NEEDED libboost_thread.so.1.46.1
  NEEDED libboost_filesystem.so.1.46.1
  NEEDED libboost_program_options.so.1.46.1
  NEEDED libpthread.so.0
  NEEDED libboost_system.so.1.46.1
  NEEDED libstdc++.so.6
  NEEDED libgcc_s.so.1
  NEEDED libc.so.6

[Boris (starius)]

Errors on Ubuntu Lucid turned out to be nonreproducible.
So the only affected Ubuntu version is Oneiric