title: What are the useful GCC flags for C?
body: <p>Beyond setting <code>-Wall</code>, and setting <code>-std=XXX</code>, what other really useful, but less known compiler flags are there for use in C?</p>
  
  <p>I'm particularly interested in any additional warnings, and/or and turning warnings into errors in some cases to absolutely minimize any accidental type mismatches.</p>