c - Is it safe to use realloc?

Question

Some time ago a friend of mine told me not to use realloc because it's unsafe, but he couldn't tell me why, so I made some research on the subject and the nearest references to my doubt were:

1. First
2. Second

I want to know if I can continue to use realloc in my code or if it's unsafe is there any other way to reallocate memory?

Answer 1

It's perfectly safe to use realloc. It is the way to reallocate memory in a C program.

However you should always check the return value for an error condition. Don't fall into this common trap:

p = realloc(p, new_size); // don't do this!

If this fails, realloc returns NULL and you have lost access to p. Instead do this:

new_p = realloc(p, new_size);
if (new_p == NULL)
    ...handle error
p = new_p;