title: Compiling error opencv
body: <p>I'm working on opencv implemented codes which I downloaded already by svn. These codes such as SIFT or SURF and codes for opencv were working perfectly before, but suddenly I got this error while I want to compile any code concerns opencv</p>
  
  <pre><code>/usr/lib/gcc/i486-linux-gnu/4.4.3/../../../../lib/crt1.o: In function `_start':
  (.text+0x18): undefined reference to `main'
  collect2: ld returned 1 exit status
  </code></pre>
  
  <p>So how can I solve it please, I have red already some problems but they were not helpful with my case, such as I have to change the compilation code from <code>g++ SIFT.cpp -o SIFT ....</code> to <code>g++ -o SIFT SIFT.cpp ....</code> but it didn't work out with me.</p>
  
  <p>Thank you.  </p>