Undefined reference to omp_get_thread_num using OpenMP?

Applications Programming
1

I am using a large code-base that compiled successfully before using

make

with a makefile and cmake. However, now that I'm trying to use openmp with it, I'm now getting the errors

undefined reference to `omp_get_thread_num'
    undefined reference to `omp_get_num_threads'

I don't think this is a problem with tthe CMakeLists.txt file, because I created a seperate directory and successfully built and compiled a helloworld OpenMP program. So what is causing this error?

I edited the CMakeLists.txt in

project/src/project

so to include

-fopenmp

so it contains the line

set(CMAKE_CXX_FLAGS "-Wall -pedantic -Wextra -fopenmp")
     ....
      TARGET_LINK_LIBRARIES(PROJECT  ${OpenMP_CXX_LIBRARIES} ${PROJECT_LINK_LIBS}).

The CMakeLists.txt already has the lines

FIND_PACKAGE( OpenMP)
      if(OPENMP_FOUND)
         message("OPENMP FOUND")
         set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${OpenMP_C_FLAGS}")
         set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${OpenMP_CXX_FLAGS}")
         set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} ${OpenMP_EXE_LINKER_FLAGS}")
      endif()
     include_directories(SYSTEM ${OpenMP_INCLUDE_PATH})

Although if I type

cmake ..

, I see the output

OPENMP FOUND

, I don't see

fopenmp

in any of the makefiles and I didn't see

CXXFLAGS

OR

LDFLAGS

in any of the makefiles.