link error with gold in kdebase

Andreas Hartmetz ahartmetz at
Mon May 31 17:02:05 BST 2010

On Monday 31 May 2010 17:41:31 Andreas Hartmetz wrote:
> On Sunday 30 May 2010 16:53:38 Tobias Koenig wrote:
> > Hej,
> > 
> > since the recent changes to nepomuk, kdebase doesn't compile any longer
> > with gold linker:
> > 
> > Linking CXX shared module ../../../../lib/
> > /usr/bin/ld: warning: hidden symbol
> > 'DBusConnectionPool::threadConnection()' in
> > CMakeFiles/nepomukfilewatch.dir/__/__/common/dbusconnectionpool.o is
> > referenced by DSO /opt/kde-trunk/lib/ /usr/bin/ld:
> > error: treating warnings as errors
> > collect2: ld returned 1 exit status
> > make[2]: *** [lib/] Error 1
> > make[1]: ***
> > [runtime/nepomuk/services/filewatch/CMakeFiles/nepomukfilewatch.dir/all]
> > Error 2 make: *** [all] Error 2
> > 
> > Any idea how to fix it?
> I get the same error. DBusConnectionPool::threadConnection() exists in both
> kdelibs and kdebase, which might somehow confuse gold. The whole thread-
> connection thing is a bit ugly because, AFAIK, it is a workaround for a
> libdbus bug. Due to that it is questionable if it should be part of any
> official API and of the public interface of kdelibs.
> AFAICS it should be OK that the symbol is hidden in the object file
> dbusconnectionpool.o; otherwise one couldn't link together any object files
> that use each other's hidden symbols. Hidden symbols are only supposed to
> be hidden from the end product, the .so file (right?).
> I'm not sure if it's OK that there are two eligible definitions of the
> symbol, the exported one from kdelibs and the hidden one from kdebase.
> I have fixed the problem locally by installing the header from kdelibs that
> exports  DBusConnectionPool::threadConnection() and deleting the copy in
> kdebase. This is not generally applicable until a decision about the
> correct basic approach to the libdbus bug is made.

I should have read the actual error message:
gold complains about
/opt/kde-trunk/lib/ trying to use the hidden symbol 
 'DBusConnectionPool::threadConnection()' from someplace that is not (where it is exported == has default visibility).
I don't know why gold tries to resolve symbols of *used* libraries at all - 
possibly to prevent runtime errors. This is strange because gold also tries to 
be as fast as possible.
Additionally it warns (fatally, due to --fatal-warnings) about a symbol being 
hidden in one place even though it is not hidden in another. is 
actually in the list of linked libraries, so gold should find it and its  

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