Linker Issues with boost::thread under linux using Eclipse and CMake - linux

Question

I'm in the process of attempting to port some code across from PC to Ubuntu, and am having some issues due to limited experience developing under linux.
We use CMake to generate all our build stuff. Under windows I'm making VS2010 projects, and under Linux I'm making Eclipse projects. I've managed to get my OpenCV stuff ported across successfully, but am having major headaches trying to port my threaded boost apps.
Just so we're clear, the steps I have followed so-far on a clean Ubuntu 12 installation. (I've done 2 clean re-installs to try and fix potential library cock-ups, now I'm just giving up and asking):
Install Eclipse and Eclipse CDT using my package manager
Install CMake and CMake Gui using my package manager
Install libboost-all-dev using my package manager
So-far that's all I've done. I can create the eclipse project using CMake with no errors, so CMake is successfully finding my boost install. When I try and build through eclipse is when I get issues; The app I'm attempting to build uses boost::asio for some UDP I/O and boost::thread to create worker threads for the asio I/O services. I can successfully compile each module, but when I come to link I get spammed with errors such as:
/usr/bin/c++ CMakeFiles/RE05DevelopmentDemo.dir/main.cpp.o CMakeFiles/RE05DevelopmentDemo.dir/RE05FusionListener/RE05FusionListener.cpp.o CMakeFiles/RE05DevelopmentDemo.dir/NewEye/NewEye.cpp.o -o RE05DevelopmentDemo -rdynamic -Wl,-Bstatic -lboost_system-mt -lboost_date_time-mt -lboost_regex-mt -lboost_thread-mt -Wl,-Bdynamic
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../../lib/libboost_thread-mt.a(thread.o): In function `void boost::call_once<void (*)()>(boost::once_flag&, void (*)()) [clone .constprop.98]':
make[2]: Leaving directory `/home/david/Code/Build/Support/RE05DevDemo'
(.text+0xc8): undefined reference to `pthread_key_create'
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../../lib/libboost_thread-mt.a(thread.o): In function `boost::this_thread::interruption_enabled()':
(.text+0x540): undefined reference to `pthread_getspecific'
make[1]: Leaving directory `/home/david/Code/Build/Support/RE05DevDemo'
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../../lib/libboost_thread-mt.a(thread.o): In function `boost::this_thread::disable_interruption::disable_interruption()':
(.text+0x570): undefined reference to `pthread_getspecific'
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../../lib/libboost_thread-mt.a(thread.o): In function `boost::this_thread::disable_interruption::disable_interruption()':
(.text+0x59f): undefined reference to `pthread_getspecific'
Some Gotchas that I have collected from other StackOverflow posts and have already checked:
The boost libs are all present at /usr/lib
I am not getting any compile errors for inability to find the boost headers, so they must be getting found.
I am trying to link statically, but I believe eclipse should be passing the correct arguments to make that happen since my CMakeLists.txt includes SET(Boost_USE_STATIC_LIBS ON)
I'm officially out of ideas here, I have tried doing local builds of boost and a bunch of other stuff with no more success. I even re-installed Ubuntu to ensure I haven't completely fracked the libs directories and links with multiple weird versions or anything else. Any help would be muchly appreciated.

Answer 1

Correct mechanism is to use Threads package:
find_package(Threads)
#...
target_link_libraries(my_app ${CMAKE_THREAD_LIBS_INIT} ...)
See also cmake and libpthread

Answer 2

When you are building your targets, add -lpthread and it will compile.
See this other thread.

Answer 3

OK, so I found the solution.
It was to do with the absence of the -lpthread flag in the link command. In order to get CMake to link appropriately, then the TARGET_LINK_LIBRARIES line needs to be edited. My edit is:
Original:
TARGET_LINK_LIBRARIES( RE05DevelopmentDemo ${Boost_LIBRARIES} )
Modified and working:
IF(WIN32)
TARGET_LINK_LIBRARIES( RE05DevelopmentDemo ${Boost_LIBRARIES} )
ELSE(WIN32)
TARGET_LINK_LIBRARIES( RE05DevelopmentDemo ${Boost_LIBRARIES} pthread )
ENDIF(WIN32)
I'm guessing that I should probably change the ELSE(WIN32) to an elseif for or use the CMake command FindThreads to link in pthread if needed, but I'm not sure how to do that at the moment and have more imporatant things on my plate given the time I've lost. Interestingly enough, I noticed my link command now has two -lpthread flags appended at the end, one after another, but everything is still compiling quite happily.