cmake set linker flags for boost - linker

Question

I'm trying to compile a boost tutorial example from http://www.boost.org/doc/libs/1_36_0/doc/html/boost_asio/tutorial/tuttimer1.html.
My CMakeLists.txt looks like the following:
project(boost)
add_executable(timer1 timer1.cpp)
set_target_properties(timer1 PROPERTIES LINK_FLAGS -lboost_system,-lpthread)
trying to build the whole thing with cmake, I get:
/var/www/C++/boost/build$ make
-- Configuring done
-- Generating done
-- Build files have been written to: /var/www/C++/boost/build
Scanning dependencies of target timer1
[100%] Building CXX object CMakeFiles/timer1.dir/timer1.cpp.o
Linking CXX executable timer1
/usr/bin/ld: cannot find -lboost_system,-lpthread
collect2: ld returned 1 exit status
make[2]: *** [timer1] Błąd 1
make[1]: *** [CMakeFiles/timer1.dir/all] Błąd 2
make: *** [all] Błąd 2
But when I run:
g++ timer1.cpp -lboost_system -lpthread -o timer1
manually, everything works fine. Can someone please point me on what do I do wrong?
PS
When I try to use solution described in Turning on linker flags with CMake, I add to cmake the following lines:
set(CMAKE_SHARED_LINKER_FLAGS "-lboost_system,-lpthread")
set(CMAKE_MODULE_LINKER_FLAGS "-lboost_system,-lpthread")
set(CMAKE_EXE_LINKER_FLAGS "-lboost_system,-lpthread")
and I get the same error as above.

Answer 1

I strongly suggest that you use the CMake integrated FindPackage. CMake will find boost and pthreads for you.
Your CMakeLists.txt should look like this:
find_package( Boost COMPONENTS thread system filesystem REQUIRED ) #whatever libs you need
include_directories( ${Boost_INCLUDE_DIRS} )
find_package( Threads )
In the subfolder src:
set( LIBS_TO_LINK
${Boost_LIBRARIES}
${CMAKE_THREAD_LIBS_INIT}
)
target_link_libraries( myApp
${LIBS_TO_LINK}
)

Answer 2

/usr/bin/ld: cannot find -lboost_system,-lpthread
Here the linker is looking for a library libboost_system,-lpthread.so. It is exceedingly unlikely that such a library exists on any UNIX system.
You probably want:
set(CMAKE_EXE_LINKER_FLAGS "-lboost_system -lpthread")