title: How do I get available memory from lwIP's mem_malloc?
body: <p>I'm using lwIP on an embedded device, and I feel that I may be running into some bugs related to running out of memory. I know that the mem_malloc function itself will return null when a memory allocation fails, but is there any way to get a rough assessment of the available memory at an arbitrary point in time? It would be great to be able to monitor it directly, to determine which usage patterns are leaking memory.</p>
  
  <p>Thanks.</p>