target_link_libraries for lpthread, ldl, and lutils

albertchristianto · May 19, 2020, 8:27am

Hello, i am new at using cmake for compiling and building c++ code.

here is my CMakeLists.txt

cmake_minimum_required(VERSION 3.0)
project(example)
add_subdirectory(pybind11)

find_package( Threads REQUIRED )
#find_package( OpenCV REQUIRED )

include_directories( ${OpenCV_INCLUDE_DIRS})

set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
set(CMAKE_CXX_EXTENSIONS OFF)

add_executable(demo demo_python.cpp)

target_link_libraries(demo ${CMAKE_THREAD_LIBS_INIT} ${CMAKE_DL_LIBS})

target_link_libraries(demo pybind11::embed)# ${OpenCV_LIBS})

i have checked and ensured that my computer has the required library. and i am keep getting this error, which say that i haven’t linked pthread, ldl, and lutil.

/usr/local/lib/libpython3.7m.a(thread.o): In function `PyThread_tss_create':
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:750: undefined reference to `pthread_key_create'
/usr/local/lib/libpython3.7m.a(thread.o): In function `PyThread_tss_delete':
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:767: undefined reference to `pthread_key_delete'
/usr/local/lib/libpython3.7m.a(thread.o): In function `PyThread_start_new_thread':
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:222: undefined reference to `pthread_create'
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:239: undefined reference to `pthread_detach'
/usr/local/lib/libpython3.7m.a(thread.o): In function `PyThread_acquire_lock_timed':
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:372: undefined reference to `sem_wait'
/usr/local/lib/libpython3.7m.a(thread.o): In function `PyThread_start_new_thread':
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:203: undefined reference to `pthread_attr_setstacksize'
/usr/local/lib/libpython3.7m.a(thread.o): In function `PyThread_tss_delete':
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:767: undefined reference to `pthread_key_delete'
/usr/local/lib/libpython3.7m.a(thread.o): In function `_pythread_pthread_set_stacksize':
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:640: undefined reference to `pthread_attr_setstacksize'
/usr/local/lib/libpython3.7m.a(thread.o): In function `PyThread_create_key':
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:677: undefined reference to `pthread_key_create'
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:682: undefined reference to `pthread_key_delete'
/usr/local/lib/libpython3.7m.a(thread.o): In function `PyThread_set_key_value':
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:712: undefined reference to `pthread_setspecific'
/usr/local/lib/libpython3.7m.a(thread.o): In function `PyThread_delete_key':
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:696: undefined reference to `pthread_key_delete'
/usr/local/lib/libpython3.7m.a(thread.o): In function `PyThread_delete_key_value':
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:704: undefined reference to `pthread_setspecific'
/usr/local/lib/libpython3.7m.a(thread.o): In function `PyThread_get_key_value':
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:723: undefined reference to `pthread_getspecific'
/usr/local/lib/libpython3.7m.a(thread.o): In function `PyThread_allocate_lock':
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:292: undefined reference to `sem_init'
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:292: undefined reference to `sem_init'
/usr/local/lib/libpython3.7m.a(thread.o): In function `PyThread_free_lock':
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:317: undefined reference to `sem_destroy'
/usr/local/lib/libpython3.7m.a(thread.o): In function `PyThread_acquire_lock_timed':
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:369: undefined reference to `sem_trywait'
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:369: undefined reference to `sem_trywait'
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:372: undefined reference to `sem_wait'
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:372: undefined reference to `sem_wait'
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:369: undefined reference to `sem_trywait'
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:372: undefined reference to `sem_wait'
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:369: undefined reference to `sem_trywait'
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:369: undefined reference to `sem_trywait'
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:369: undefined reference to `sem_trywait'
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:372: undefined reference to `sem_wait'
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:369: undefined reference to `sem_trywait'
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:366: undefined reference to `sem_timedwait'
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:372: undefined reference to `sem_wait'
/usr/local/lib/libpython3.7m.a(thread.o): In function `PyThread_release_lock':
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:441: undefined reference to `sem_post'
/usr/local/lib/libpython3.7m.a(thread.o): In function `PyThread_tss_set':
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:776: undefined reference to `pthread_setspecific'
/usr/local/lib/libpython3.7m.a(thread.o): In function `PyThread_tss_get':
/home/ion/Documents/Python-3.7.7/Python/thread_pthread.h:784: undefined reference to `pthread_getspecific'
/usr/local/lib/libpython3.7m.a(dynload_shlib.o): In function `_PyImport_FindSharedFuncptr':
/home/ion/Documents/Python-3.7.7/./Python/dynload_shlib.c:96: undefined reference to `dlopen'
/home/ion/Documents/Python-3.7.7/./Python/dynload_shlib.c:127: undefined reference to `dlsym'
/home/ion/Documents/Python-3.7.7/./Python/dynload_shlib.c:102: undefined reference to `dlerror'
/home/ion/Documents/Python-3.7.7/./Python/dynload_shlib.c:96: undefined reference to `dlopen'
/home/ion/Documents/Python-3.7.7/./Python/dynload_shlib.c:83: undefined reference to `dlsym'
/usr/local/lib/libpython3.7m.a(posixmodule.o): In function `os_forkpty_impl':
/home/ion/Documents/Python-3.7.7/./Modules/posixmodule.c:6048: undefined reference to `forkpty'
/usr/local/lib/libpython3.7m.a(posixmodule.o): In function `os_openpty_impl':
/home/ion/Documents/Python-3.7.7/./Modules/posixmodule.c:5954: undefined reference to `openpty'
/usr/local/lib/libpython3.7m.a(signalmodule.o): In function `signal_pthread_sigmask_impl':
/home/ion/Documents/Python-3.7.7/./Modules/signalmodule.c:855: undefined reference to `pthread_sigmask'
/usr/local/lib/libpython3.7m.a(signalmodule.o): In function `signal_pthread_kill_impl':
/home/ion/Documents/Python-3.7.7/./Modules/signalmodule.c:1124: undefined reference to `pthread_kill'
/usr/local/lib/libpython3.7m.a(timemodule.o): In function `time_pthread_getcpuclockid':
/home/ion/Documents/Python-3.7.7/./Modules/timemodule.c:342: undefined reference to `pthread_getcpuclockid'
/usr/local/lib/libpython3.7m.a(faulthandler.o): In function `faulthandler_thread':
/home/ion/Documents/Python-3.7.7/./Modules/faulthandler.c:564: undefined reference to `pthread_sigmask'
collect2: error: ld returned 1 exit status
CMakeFiles/demo.dir/build.make:84: recipe for target 'demo' failed
make[2]: *** [demo] Error 1
CMakeFiles/Makefile2:95: recipe for target 'CMakeFiles/demo.dir/all' failed
make[1]: *** [CMakeFiles/demo.dir/all] Error 2
Makefile:83: recipe for target 'all' failed
make: *** [all] Error 2

Please help me. I am very frustrated and tired because of this error. i have spent 2 days of ssearching and trying with no result.
thank you very much.

best regards,
Albert Christianto

ben.boeckel · May 19, 2020, 10:37am

Could you post the link line that gets used for that link step and the value of the variables in the target_link_libraries?

albertchristianto · May 25, 2020, 7:07am

Hi @ben.boeckel,
Sorry for my late response because I was distracted on another task.
Thank you very much for your responses. Actually, I have successfully solved it in 3 hours after i posted this question. It turns out, the problem is in my own python interpreter library which hasn’t been linked with pthread libs, dl libs, and utility libs correctly.

However, i am quite confuse though why i can’t force my own apps to be linked with these 3 libraries.
So, the value of the variables in the target_link_libraries
here is my CMakeLists.txt

cmake_minimum_required(VERSION 3.0)
project(example)
add_subdirectory(pybind11)

find_package( Threads REQUIRED )
#find_package( Utils REQUIRED )

include_directories( ${OpenCV_INCLUDE_DIRS})

message(${CMAKE_THREAD_LIBS_INIT})#pthread library
message(${CMAKE_DL_LIBS})#dl libs
#message(lutil)#utility libs
message(pybind11::embed)#pybind library

set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
set(CMAKE_CXX_EXTENSIONS OFF)

add_executable(demo demo_python.cpp)

target_link_libraries(demo ${CMAKE_THREAD_LIBS_INIT} ${CMAKE_DL_LIBS} lutil)

target_link_libraries(demo pybind11::embed)

and here the output of the cmake

-- The C compiler identification is GNU 5.4.0
-- The CXX compiler identification is GNU 5.4.0
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found PythonInterp: /usr/bin/python3.7 (found version "3.7.7")
-- Found PythonLibs: /usr/lib/libpython3.7m.so
-- Performing Test HAS_CPP14_FLAG
-- Performing Test HAS_CPP14_FLAG - Success
-- pybind11 v2.4.dev4
-- Looking for pthread.h
-- Looking for pthread.h - found
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD - Failed
-- Looking for pthread_create in pthreads
-- Looking for pthread_create in pthreads - not found
-- Looking for pthread_create in pthread
-- Looking for pthread_create in pthread - found
-- Found Threads: TRUE
pthread
dl
pybind11::embed
-- Configuring done
-- Generating done
-- Build files have been written to: /home/ion/Documents/embed_python

and I am still don’t know what the flags is for lutil in cmake.

best regards,
Albert Christianto

ben.boeckel · May 25, 2020, 8:57pm

You probably just want util, not lutil. The first l is part of the flags to tell it what library to link to.

albertchristianto · May 28, 2020, 3:45am

hi @ben.boeckel,
Thank you. Now i know the cmake flag for the utility library.
so right now i can’t reproduce the error, since i have fixed the python library.
I will try to read CMake documentation once again to fix my lacks of knowledge in CMake. ^v^
best regards,
Albert Christianto