What is the correct usage of realloc() when it fails and returns NULL?

Question

Can anyone summarize what is the correct usage of realloc()?

What do you do when realloc() fails?

From what I have seen so far, it

Answer 1

From http://www.c-faq.com/malloc/realloc.html

If realloc cannot find enough space at all, it returns a null pointer, and leaves the previous region allocated.

Therefore you would indeed need to free the previously allocated memory still.