15

I am trying to run simple OpenMP program in CLion IDE. When I run it I get an ERROR:

CMakeFiles\openmp_test_clion.dir/objects.a(main.cpp.obj): In function `main':
D:/.../openmp_test_clion/main.cpp:9: undefined reference to 'omp_get_thread_num'
collect2.exe: error: ld returned 1 exit status

Here is my code:

#include <stdio.h>
#include <omp.h>

int main()
{
    int id;
#pragma omp parallel private(id)
    {
        id = omp_get_thread_num();
        printf("%d: Hello World!\n", id);
    }
    return 0;
}

Here is my CMakeLists.txt:

cmake_minimum_required(VERSION 3.6)
project(openmp_test_clion)

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")

set(SOURCE_FILES main.cpp)
add_executable(openmp_test_clion ${SOURCE_FILES})

message(STATUS "Checking OpenMP")
find_package(OpenMP)
IF(OPENMP_FOUND)
    message("Found OpenMP!)
    # add flags for OpenMP
    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${OpenMP_C_FLAGS}")
    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${OpenMP_CXX_FLAGS}")
    set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} ${OpenMP_SHARED_LINKER_FLAGS}")
    set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} ${OpenMP_EXE_LINKER_FLAGS}")
ELSE()
    message("Missed OpenMP!")
ENDIF()

Here is screen of my toolchains: enter image description here

I have zero experience with OpenMP and I am beginner programmer in C++ so please give me a bit of an explanation how to setup my project.

PeterB
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1 Answers1

25

So after a while I figured it out. I changed CmakeLists.txt as following:

cmake_minimum_required(VERSION 3.6)
project(openmp_test_clion)

# added -fopenmp
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -fopenmp")

set(SOURCE_FILES main.cpp)
add_executable(openmp_test_clion ${SOURCE_FILES})

And I needed to install openmp via TDM-GCC installer .

PeterB
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    [This answer](https://stackoverflow.com/a/12404666/1662425) shows a better setup that supports multiple compilers, rather than hardcoding the gcc flags. – tera Feb 21 '18 at 15:59
  • Unfortunately this did not work for me. This was the only answer that worked for me on Mac OS with CLion: https://stackoverflow.com/questions/34203252/osx-and-clion-cant-find-omp-h – Shane Sepac Mar 27 '21 at 18:40