[Boost-users] [thread_safe_signals] Qt/MOC Linker problem with header-only thread_safe_signals-library

From: raimar wagner (raimar.wagner_at_[hidden])
Date: 2008-01-29 09:40:03

Hi!
I'm using the "thread_safe_signals"-library in a Qt-Context. I have a
file "foo.cpp" containing Qt-stuff which is processed by the moc
before it compiles.

foo.cpp:
> #include "foo.h"
>
> ... Qt-stuff ...
>

foo.h:
> #include "bar.h"
>
> ... Qt-declarations ..
>

bar.h:
> #include <boost/thread_safe_signal.hpp>
> #include <boost/thread_safe_signals/multi_threaded.hpp>
> #include <boost/bind.hpp>
>
> ...
>

Now the following happens:

1.) The Qt moc creates moc_foo.cpp based on foo.cpp
2.) everything compiles fine ("g++ (GCC) 4.1.0 (SUSE Linux)" using
SCons on SUSE 10.1)
3.) The linking process fails with:

> build/release/src/foo.os: In function `boost::signalslib::null_deleter(void const*)':
> /path_to_boost/include/boost/thread_safe_signals/connection.hpp:42: multiple definition of `
> boost::signalslib::null_deleter(void const*)'
> build/release/src/bar.os:/path_to_boost/include/boost/thread_safe_signals/connection.hpp:42: first
> defined here
> build/release/src/foo_moc.os: In function `boost::signalslib::null_deleter(void const*)':
> /path_to_boost/include/boost/thread_safe_signals/connection.hpp:42: multiple definition of
> `boost::signalslib::null_deleter(void const*)'
> build/release/src/bar.os:/path_to_boost/include/boost/thread_safe_signals/connection.hpp:42: first
> defined here
> collect2: ld returned 1 exit status

Our workaround was to edit connection.hpp from:

42: > void null_deleter(const void*) {}

to

42: > void null_deleter(const void*);

and add to bar.cpp:

> namespace boost
> {
>         namespace signalslib
>         {
>                 void null_deleter(const void*) {}
> 	}
> }

This works, but maybe there is a better solution to cope with this
problem. Any ideas?

Kindest regards
Raimar Wagner