title: Undefined reference for external library (C++, QT, Ubuntu 14, CCV)
body: <p>I'm trying to run the CCV library linked at <a href="http://libccv.org/" rel="nofollow">http://libccv.org/</a> in QT Creator on Ubuntu 14. I followed this tutorial <a href="http://libccv.org/tutorial/" rel="nofollow">http://libccv.org/tutorial/</a> and I'm trying now to run the first simple example. I get these errors:</p>
  
  <ul>
  <li>error: undefined reference to ccv_read_impl(void const*, ccv_dense_matrix_t**, int, int, int, int)</li>
  <li>error: undefined reference to ccv_write(ccv_dense_matrix_t*, char*, int*, int, void*)</li>
  </ul>
  
  <p>This  is the .pro file of the project:</p>
  
  <pre><code>TEMPLATE = app
  CONFIG += console
  CONFIG -= app_bundle
  CONFIG -= qt
  
  SOURCES += main.cpp
  
  unix:!macx: LIBS += -L$$PWD/../../../CNN/ccv/lib/ -lccv
  
  INCLUDEPATH += $$PWD/../../../CNN/ccv/lib
  DEPENDPATH += $$PWD/../../../CNN/ccv/lib
  
  unix:!macx: PRE_TARGETDEPS += $$PWD/../../../CNN/ccv/lib/libccv.a
  </code></pre>
  
  <p>Finally this is the command generated by QT in the compile output:</p>
  
  <ul>
  <li>g++ -m64 -o ccv1 main.o   -L/home/fabri/QT/CCV1/ccv1/../../../CNN/ccv/lib/ -lccv </li>
  </ul>
  
  <p>I suppose it's a compiler problem but I don't know what. Thank you.</p>