title: Meaning of g++ flags -Wall -W -Werror
body: <p>What are these and what do they do?</p>
  
  <pre><code>-Wall -W -Werror
  </code></pre>
  
  <p>I am using terminal in Ubuntu to compile programs with this command:</p>
  
  <pre><code>$ g++ -Wall -W -Werror main.cpp -o exec
  </code></pre>
  
  <p>Could anyone explain this to me?</p>