title: What does -Wall flag do when I compile it with the program?
body: <p>I am following a tutorial that says how to profile the program using 
  gprof and the command given is like this</p>
  
  <blockquote>
    <p>gcc -Wall -pg test_gprof.c test_gprof_new.c -o test_gprof</p>
  </blockquote>
  
  <p>But it doesn'y give any explanation for this flag (-Wall)</p>