problems with cmake and boost-signals - c++

Question

I'm using cmake for project with boost, I've set boost-signals as required and cmake states it finds it, but when I compile the project I get a linking error.
I can resolve it with a linker directive set(CMAKE_EXE_LINKER_FLAGS -lboost_signals) but
this seems contrary to what it should be doing. Can someone suggest a better way? Thanks
in CMakeLists.txt
IF(UNIX)
find_package(Boost COMPONENTS system filesystem random regex signals thread program_options date_time REQUIRED)
INCLUDE_DIRECTORIES( ${Boost_INCLUDE_DIRS} )
ENDIF()
Running cmake:
$ cmake ../
-- Boost version: 1.49.0
-- Found the following Boost libraries:
-- system
-- filesystem
-- random
-- regex
-- signals
-- thread
-- program_options
-- date_time
-- Configuring done
-- Generating done
-- Build files have been written to: /home/me/myproject/build
Linker error:
/usr/bin/ld: /usr/local/lib/libwt.so: undefined reference to symbol '_ZN5boost7signals9trackableD2Ev'
/usr/bin/ld: note: '_ZN5boost7signals9trackableD2Ev' is defined in DSO /usr/lib/libboost_signals.so.1.49.0 so try adding it to the linker command line
/usr/lib/libboost_signals.so.1.49.0: could not read symbols: Invalid operation
collect2: error: ld returned 1 exit status

Answer 1

Boost Signals is not a header-only library. In addition to giving the include directory, you need to tell CMake to link against it too.
add_executable(MyProgram [...] )
target_link_libraries(MyProgram ${Boost_LIBRARIES})
In case you plan to build on Windows as well, you might also want to disable auto-linking:
add_definitions(-DBOOST_ALL_NO_LIB)
Note that Boost Signals has been deprecated and replaced by Signals2, which is in fact a header-only library. If it is up to you to make the choice, consider using Signals2 instead.