title: OpenCv No rule to make target
body: <p>this is my first example with OpenCv:</p>
  
  <pre><code>    #include &lt;stdlib.h&gt;
  #include &lt;stdio.h&gt;
  #include &lt;math.h&gt;
  #include "opencv/cv.h"
  #include "opencv/highgui.h"
  
  int main(int argc, char *argv[])
  {
    IplImage* img = 0;
  
    img=cvLoadImage("/home/michele/Pictures/sensor.png");     // carica l'immagine
  
    cvNamedWindow("mainWin", CV_WINDOW_AUTOSIZE);       // crea la finestra
  
    cvShowImage("mainWin", img );    //  mostra l'immagine
  
    cvWaitKey(0);    // wait for a key
  
    cvReleaseImage(&amp;img );    //rilascia l'immagine
  
    system("PAUSE");
    return 0;
  }
  </code></pre>
  
  <p>If I click on BuildAll I've this error returned:</p>
  
  <pre><code>make: *** No rule to make target `1st.o', needed by `firstOpenCV'.  Stop.
  </code></pre>
  
  <p>What I have to do?</p>
  
  <p>Thanks.</p>