title: What Does This Valgrind Warning Mean? - warning set address range perms
body: <p>When I was running my program against valgrind, I encountered the following warning.</p>
  
  <pre><code>Warning: set address range perms: large range [0x4d59d040, 0x6159d040) (undefined)
  Warning: set address range perms: large range [0x194f7030, 0x2d4f7050) (noaccess)
  Warning: set address range perms: large range [0x3959d030, 0x6159d050) (noaccess)
  </code></pre>
  
  <p>After some googling I found at <a href="http://www.network-theory.co.uk/docs/valgrind/valgrind_29.html">here</a> that it is a <code>Diagnostic message, mostly for benefit of the Valgrind developers, to do with memory permissions</code>, which doesn't tell me much.</p>
  
  <p>My program does allocate a large amount of memory on heap. (Can reach 2-3 GB of ram after a whole bunch of <code>realloc</code>'s)</p>
  
  <p>However, the warning appeared despite none of the allocations failed.</p>
  
  <p>So, I'm wondering what this message really means? I don't have some sort of memory permission? (But allocation succeeded) </p>