is it necessary to call pointer = NULL when initializing?
when I create a pointer to certain struct, do I have to set it to NULL, then alloc it then use it? and why?
Answer
No, you don't have to set it to NULL, but some consider it good practice as it gives a new pointer a value that makes it explicit it's not pointing at anything (yet).
If you are creating a pointer and then immediately assigning another value to it, then there's really not much value in setting it to NULL.
It is a good idea to set a pointer to NULL after you free the memory it was pointing to, though.