title: What does equals sign g "=g" in GCC inline assembly mean / do?
body: <p>I'm not sure what this inline assembly does:</p>
  
  <pre><code>asm ("mov %%esp, %0" : "=g" (esp));
  </code></pre>
  
  <p>especially the <code>: "=g" (esp)</code> part.</p>