Strange linking problem with 11.2

English Open Build Service (OBS)
1

I’m building IM client called kadu (home:zawel1:kadu) in OSC. This project compiles some plugins (shared libraries loaded on demand by main program). One of them relies on libXss which is linked with (apparent) success:
line

/usr/bin/c++  -fPIC -O3 -DNDEBUG -lXss -shared -Wl,-soname,libidle.so -o libidle.so CMakeFiles/idle.dir/idle.cpp.o CMakeFiles/idle.dir/idle_x11.cpp.o CMakeFiles/idle.dir/moc_idle.cxx.o -Ldocking -Lqt4_docking

goes without a problem. But resulting libidle.so from final rpm for 11.2 haven’t got Xss linked:

 pc028:/pub/zawel # ldd libidle.so 
        linux-gate.so.1 =>  (0xffffe000)             
        libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0xb75da000)
        libgcc_s.so.1 => /lib/libgcc_s.so.1 (0xb75ba000)      
        libc.so.6 => /lib/libc.so.6 (0xb745a000)              
        libm.so.6 => /lib/libm.so.6 (0xb7431000)              
        /lib/ld-linux.so.2 (0xb7716000)

What is more strange, when I compile this rpm on my own machine the Xss IS linked:

pc028:/pub/zawel # ldd libidle.so 
        linux-gate.so.1 =>  (0xffffe000)                                            
        libXss.so.1 => /usr/lib/libXss.so.1 (0xb7793000)                            
        libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0xb769f000)                      
        libm.so.6 => /lib/libm.so.6 (0xb7676000)                                    
        libgcc_s.so.1 => /lib/libgcc_s.so.1 (0xb7656000)                            
        libc.so.6 => /lib/libc.so.6 (0xb74f5000)                                    
        libX11.so.6 => /usr/lib/libX11.so.6 (0xb73c0000)                            
        libXext.so.6 => /usr/lib/libXext.so.6 (0xb73ae000)                          
        /lib/ld-linux.so.2 (0xb77df000)                                             
        libxcb.so.1 => /usr/lib/libxcb.so.1 (0xb738f000)                            
        libdl.so.2 => /lib/libdl.so.2 (0xb738a000)                                  
        libXau.so.6 => /usr/lib/libXau.so.6 (0xb7385000)

Any ideas what can be wrong with OSC compilation? Rpms for other suse versions (11.0, 11.1) are properly compiled.
ZAWEL

2

man ld and search for --as-needed, it is used by default since openSUSE 11.2.

You can also search in the man page for “-l namespec”. In the third paragraph you can see that your link command is wrong even if it happens to work.

When -lXss is read the linker sees that it doesn’t provides any symbol needed by any previous object, so ignores it. If it is really needed put it AFTER the .o’s.

3

Thank you for pointing me --as-needed, this way I found the bug in compilation scrips. This command come from Makefile which in turn was generated by cmake. The real error was that -lXss was added to properties LINK_FLAGS and not via target_link_libraries(). I’ve corrected that and everything looks ok now. I will send info to original authors of the software. Thanks again for quick reply.