Undefined reference to "function name from external library" - c++

Question

I'm using Ubuntu 12 64 bit, installed fftw library version 2.1.5.
I have a c++ project with use CMake to build the make file. This is my cmakelist.text:
project(MP)
cmake_minimum_required(VERSION 2.8)
if(TYPE STREQUAL "Debug")
set(CMAKE_BUILD_TYPE "Debug")
else()
set(CMAKE_BUILD_TYPE "Release")
endif()
if(CMAKE_COMPILER_IS_GNUCXX)
add_definitions( -std=c++11 )
endif()
find_package(GLUT REQUIRED)
find_package(OpenGL REQUIRED)
find_library(GLUI libglui.a ./vendor/lib)
include_directories(${OPENGL_INCLUDE_DIR}
./vendor/include)
LINK_DIRECTORIES(/usr/local/lib)
LINK_DIRECTORIES(/usr/lib)
LINK_DIRECTORIES(/usr/bin)
aux_source_directory(. SRC_LIST)
add_executable(${PROJECT_NAME} ${SRC_LIST})
target_link_libraries(${PROJECT_NAME} GL GLU glut ${GLUI})
When I tried running the make file create by Cmake, i got this problem:
CMakeFiles/SciVis.dir/Simulation.cc.o: In function `Simulation::init_simulation(unsigned long)':
Simulation.cc:(.text+0x2d5): undefined reference to `rfftw2d_create_plan'
Simulation.cc:(.text+0x2ee): undefined reference to `rfftw2d_create_plan'
CMakeFiles/SciVis.dir/Simulation.cc.o: In function `Simulation::solve()':
Simulation.cc:(.text+0x881): undefined reference to `rfftwnd_one_real_to_complex'
Simulation.cc:(.text+0x891): undefined reference to `rfftwnd_one_real_to_complex'
Simulation.cc:(.text+0xa7f): undefined reference to `rfftwnd_one_complex_to_real'
Simulation.cc:(.text+0xa8f): undefined reference to `rfftwnd_one_complex_to_real'
CMakeFiles/SciVis.dir/Simulation.cc.o: In function `Simulation::FFT(int, void*)':
Simulation.cc:(.text+0x390): undefined reference to `rfftwnd_one_complex_to_real'
Simulation.cc:(.text+0x3a0): undefined reference to `rfftwnd_one_real_to_complex'
collect2: error: ld returned 1 exit status
make[2]: *** [SciVis] Error 1
make[1]: *** [CMakeFiles/SciVis.dir/all] Error 2
make: *** [all] Error 2
In my Simulation.cc file:
#include <fftw.h>
void Simulation::init_simulation(size_t n)
{
//Allocate data structures
size_t dim = n * 2 * (n / 2 + 1);
vx = new fftw_real[dim];
vy = new fftw_real[dim];
vx0 = new fftw_real[dim];
vy0 = new fftw_real[dim];
fx = new fftw_real[n * n];
fy = new fftw_real[n * n];
rho = new fftw_real[n * n];
rho0 = new fftw_real[n * n];
plan_rc = rfftw2d_create_plan(n, n, FFTW_REAL_TO_COMPLEX, FFTW_IN_PLACE);
plan_cr = rfftw2d_create_plan(n, n, FFTW_COMPLEX_TO_REAL, FFTW_IN_PLACE);
// Initialize data structures to 0
for (size_t i = 0; i < n * n; i++)
{
vx[i] = vy[i] = vx0[i] = vy0[i] = fx[i] = fy[i] = rho[i] = rho0[i] = 0.0f;
}
}
void Simulation::FFT(int direction,void* vx)
{
if(direction==1) rfftwnd_one_real_to_complex(plan_rc,(fftw_real*)vx,(fftw_complex*)vx);
else rfftwnd_one_complex_to_real(plan_cr,(fftw_complex*)vx,(fftw_real*)vx);
}
I dont know where I were wrong, can someone please help me ?
Thank you very much.

Answer 1

You're not linking against FFTW, you need to make CMake find the library and link against it first, put this file in your project's directory under a new folder "CMakeModules".
FindFFTW.cmake
# - Find FFTW
# Find the native FFTW includes and library
#
# FFTW_INCLUDES - where to find fftw3.h
# FFTW_LIBRARIES - List of libraries when using FFTW.
# FFTW_FOUND - True if FFTW found.
if (FFTW_INCLUDES)
# Already in cache, be silent
set (FFTW_FIND_QUIETLY TRUE)
endif (FFTW_INCLUDES)
find_path (FFTW_INCLUDES fftw3.h)
find_library (FFTW_LIBRARIES NAMES fftw3)
# handle the QUIETLY and REQUIRED arguments and set FFTW_FOUND to TRUE if
# all listed variables are TRUE
include (FindPackageHandleStandardArgs)
find_package_handle_standard_args (FFTW DEFAULT_MSG FFTW_LIBRARIES FFTW_INCLUDES)
mark_as_advanced (FFTW_LIBRARIES FFTW_INCLUDES)
Next, add this line to the top of your CMakeLists.txt:
project(MP)
cmake_minimum_required(VERSION 2.8)
set(CMAKE_MODULE_PATH "${CMAKE_SOURCE_DIR}/CMakeModules" ${CMAKE_MODULE_PATH})
Now try this:
find_package(FFTW REQUIRED)
include_directories(${OPENGL_INCLUDE_DIR} ${FFTW_INCLUDES}
./vendor/include)
...
target_link_libraries(${PROJECT_NAME} GL GLU glut ${GLUI} ${FFTW_LIBRARIES})