Linking Boost thread library

Question

I am trying to include Boost's thread library in my C++ project. My CMake file is like so:

cmake_minimum_required(VERSION 3.6)
project(LearningC)

find_package(Boost REQUIRED)
include_directories(${Boost_INCLUDE_DIR})

set(CMAKE_CXX_STANDARD 11)

set(SOURCE_FILES main.cpp Student.cpp Student.h)

add_executable(LearningC ${SOURCE_FILES})

target_link_libraries(LearningC ${Boost_LIBRARIES})

I get an error:

Undefined symbols for architecture x86_64:
  "boost::this_thread::interruption_point()", referenced from:
      boost::condition_variable::wait(boost::unique_lock<boost::mutex>&) in main.cpp.o
   [More stack traces...]

What am I doing wrong?

Answer 1

Ok, I see you've found a solution, but there are some improvements I'd like to propose (as soon as you require CMake 3.6):

• use imported targets to manage compiler/linker options per target, instead of "global" variables and functions (like include_directories() , ...)
• use full signature of project() to define a bunch of PROJECT_xxx variables, then use them
• provide explicit list of languages do you use to avoid default and possible redundant checks
• in case of Boost, you don't need to find and link with implicit dependencies -- FindBoost.cmake would do it for you. Just specify components only what you really need and use.

Here is a modified CMakeLists.txt :

cmake_minimum_required(VERSION 3.6)
project(LearningCxx VERSION 1.0.0 LANGUAGES CXX)

set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

find_package(Boost COMPONENTS thread REQUIRED)

add_executable(
    ${PROJECT_NAME}
    main.cpp
    Student.cpp
  )

target_link_libraries(
    ${PROJECT_NAME}
    Boost::thread
  )

---

Update: I've done an example for this project, but remove Students.cpp and replace main.cpp with the following code:

#include <boost/thread.hpp>
#include <iostream>

int main()
{
    std::cout << boost::thread::hardware_concurrency() << std::endl;
}

Here is my test run:

zaufi@gentop〉…/tests/boost-thread-cmake/build〉empty dir〉cmake ..
-- The CXX compiler identification is GNU 5.4.0
-- Check for working CXX compiler: /usr/lib/outproc/bin/c++ -- works
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features - done
-- Looking for C++ include pthread.h - found
-- Looking for pthread_create - not found
-- Looking for pthread_create in pthreads - not found
-- Looking for pthread_create in pthread - found
-- Found Threads: TRUE
-- Boost version: 1.62.0
-- Found the following Boost libraries:
--   thread
--   chrono
--   system
--   date_time
--   atomic
-- Configuring done
-- Generating done
-- Build files have been written to: /work/tests/boost-thread-cmake/build
zaufi@gentop〉…/tests/boost-thread-cmake/build〉default〉pfx: /usr/local〉make
Scanning dependencies of target LearningCxx
[ 50%] Building CXX object CMakeFiles/LearningCxx.dir/main.cpp.o
[100%] Linking CXX executable LearningCxx
[100%] Built target LearningCxx
zaufi@gentop〉…/tests/boost-thread-cmake/build〉default〉pfx: /usr/local〉ldd ./LearningCxx
        linux-vdso.so.1 (0x00007fff73b75000)
        libboost_thread.so.1.62.0 => /usr/lib64/libboost_thread.so.1.62.0 (0x00007fd1adafd000)
        libboost_chrono.so.1.62.0 => /usr/lib64/libboost_chrono.so.1.62.0 (0x00007fd1ad8f6000)
        libboost_system.so.1.62.0 => /usr/lib64/libboost_system.so.1.62.0 (0x00007fd1ad6f2000)
        libboost_date_time.so.1.62.0 => /usr/lib64/libboost_date_time.so.1.62.0 (0x00007fd1ad4e1000)
        libboost_atomic.so.1.62.0 => /usr/lib64/libboost_atomic.so.1.62.0 (0x00007fd1ad2df000)
        libpthread.so.0 => /lib64/libpthread.so.0 (0x00007fd1ad0c3000)
        libstdc++.so.6 => /usr/lib/gcc/x86_64-pc-linux-gnu/6.3.0/libstdc++.so.6 (0x00007fd1accc8000)
        libm.so.6 => /lib64/libm.so.6 (0x00007fd1ac9cd000)
        libgcc_s.so.1 => /usr/lib/gcc/x86_64-pc-linux-gnu/6.3.0/libgcc_s.so.1 (0x00007fd1ac7b6000)
        libc.so.6 => /lib64/libc.so.6 (0x00007fd1ac41d000)
        librt.so.1 => /lib64/librt.so.1 (0x00007fd1ac215000)
        /lib64/ld-linux-x86-64.so.2 (0x00007fd1add25000)
zaufi@gentop〉…/tests/boost-thread-cmake/build〉default〉pfx: /usr/local〉cmake --version
cmake version 3.7.1

Answer 2

I found a solution. Basically, Boost has most of its code in C++ headers (.hpp). Some of the libraries however need to be compiled and linked... The code below works!

cmake_minimum_required(VERSION 3.6)
project(LearningC)

set(CMAKE_CXX_STANDARD 11)

set(SOURCE_FILES main.cpp Student.cpp Student.h)

add_executable(LearningC ${SOURCE_FILES})

find_package(Boost COMPONENTS thread system REQUIRED)

include_directories(${Boost_INCLUDE_DIR})
target_link_libraries(LearningC ${Boost_LIBRARIES})