title: What does 'corrupted double-linked list' mean
body: <p>I've recently gotten the following error from my PHP:</p>
  
  <pre><code>WARNING: [pool www] child 42475 said into stderr: "*** glibc detected *** php-fpm: pool www: corrupted double-linked list: 0x00000000013fe680 ***"
  </code></pre>
  
  <p>I'm not very bothered by this issue, and not very interested in fixing it. 
  But I'm very interested in understanding what this error 'corrupted double-linked list' actually means, because I haven't seen it before. I believe to know what a double-linked list is, but I failed to produce a program that triggers this error. </p>
  
  <p>Could somebody provide me a short snippet of code that causes the glibc to say 'corrupted double-linked list' when I compile and execute it?</p>